Journals >Chinese Optics Letters
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2005
Volume: 3 Issue 0s
136 Article(s)
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Research Article
Biophotonics of molecular oxygen: activation efficiencies upon direct and photosensitized excitation
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With a goal of mimicking the mechanisms of the biological effect of low intensity laser radiation, we have measured the rates of oxygenation of chemical traps of singlet oxygen in air-saturated organic solvents and deuterium oxide upon direct (1270 nm) excitation of the 1Δg -> 3Σg- transition in oxygen molecules.With a goal of mimicking the mechanisms of the biological effect of low intensity laser radiation, we have measured the rates of oxygenation of chemical traps of singlet oxygen in air-saturated organic solvents and deuterium oxide upon direct (1270 nm) excitation of the 1Δg -> 3Σg- transition in oxygen molecules. The data were used for estimation of the molar absorption coefficients of oxygen corresponding to this transition. The obtained values were compared with the radiative lifetimes of singlet oxygen calculated from the quantum yields of singlet oxygen phosphorescence. The quantum efficiencies (the ratios of the photoreaction rates to the irradiation intensities) of oxygenation were compared upon porphyrin-photosensitized and direct oxygen excitation..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 1 (2005)
Photonic crystal devices for wavelength division multiplexing and slow photon generation
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Photonic crystal based nanophotonic devices have been studied for various applications. One important type of devices are optical add-drop multiplexers (OADMs) that consist of photonic crystal cavities and waveguides. We show some novel device architectures and concepts to achieve better performance for such devices anPhotonic crystal based nanophotonic devices have been studied for various applications. One important type of devices are optical add-drop multiplexers (OADMs) that consist of photonic crystal cavities and waveguides. We show some novel device architectures and concepts to achieve better performance for such devices and discuss the non-vanishing backscattering issue. We fabricate high-quality photonic crystal waveguides on silicon-on-insulator substrates toward the ultimate goal of implementing the proposed OADM. Low optical loss, slow group velocity, and high dispersion are demonstrated in the fabricated waveguides, which is of interest to slow photon generation and optical delay line applications as well..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 5 (2005)
Diode-pumped lasers with intracavity Raman conversion
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The result of experimental investigation of continuous-wave (CW) diode-pumped microchip and mini lasers with an intracavity Raman conversion in a set of crystals is presented. Self-frequency Raman conversion effect in Nd:KGW, Yb:KYW, Nd:YVO4, and Nd:BaWO4 media in these lasers has been demonstrated for the first time tThe result of experimental investigation of continuous-wave (CW) diode-pumped microchip and mini lasers with an intracavity Raman conversion in a set of crystals is presented. Self-frequency Raman conversion effect in Nd:KGW, Yb:KYW, Nd:YVO4, and Nd:BaWO4 media in these lasers has been demonstrated for the first time to our best knowledge. Diode pumped microchip lasers with intracavity Raman conversion were proposed and realized in several nitrate, tungstate, and vanadate crystals. CW Raman generation in the mini lasers pumped by an Ar laser and a diode laser was demonstrated. Laser systems based on the Raman conversion and operating at fixed wavelengths as well as in the tunable spectral range of 188-1800 nm were designed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 9 (2005)
Morphology and lateral distribution of self-organized InP islands grown on GaxIn_(1-x)P buffer layers
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The morphology of self-organized InP islands on GaInP buffer layers were probed by the whole island energy and surface energy. The island morphology was affected by Mismatch between GaxIn~~(1-x)P buffer layer and InP island (MBI). With MBI increasing, the island elongates itself. The calculation also shows that the islThe morphology of self-organized InP islands on GaInP buffer layers were probed by the whole island energy and surface energy. The island morphology was affected by Mismatch between GaxIn_(1-x)P buffer layer and InP island (MBI). With MBI increasing, the island elongates itself. The calculation also shows that the island metamorphosis was elongated with the increasing of the island volume. The morphology of different InP/GaxIn_(1-x)P systems, grown on GaAs substrate by metal organic chemical vapor deposition (MOCVD) method, was consistent with calculations. The self-organized islands at the surface of buffer layers were analyzed by scaling theories to show a periodical distribution. Buffer layers such as the mismatched GaInP on the GaAs (100) tilt to (111) 15 Celsius degree could improve the periodicity of the island separation distribution. The result also shows that the dislocations had different functions in island distribution along different directions, [110] and [1-10] directions..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 12 (2005)
Modelling nonlinear optical effects in guest-host systems
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We briefly outline a modelling strategy, combining quantum chemistry and molecular dynamics simulations, for obtaining macroscopic nonlinear optical coeffcients in guest-host systems like chromophores in solutions or in polymer matrices. The parameters required for the calculation of the macroscopic nonlinear optical pWe briefly outline a modelling strategy, combining quantum chemistry and molecular dynamics simulations, for obtaining macroscopic nonlinear optical coeffcients in guest-host systems like chromophores in solutions or in polymer matrices. The parameters required for the calculation of the macroscopic nonlinear optical property, like the chromophore number density, local field factors, and the order parameter of the chromophore molecules, are derived. These parameters, together with the molecular first hyperpolarizabilities, obtained from quantum chemistry calculations, are used to estimate the macroscopic electro-optic coeffcients. The combined approach leads to some new conclusions about the relation of the chromophore property and its solvent interactions in order to optimize the nonlinear optical coeffcient. For instance, from the simulation results a totally different notion is derived about the collective properties of octupolar molecules. We find that such molecules receive a solvent induced dipole moment that makes it possible to pole them by an external electric field, but also that they can aggregate as an effect of this solvent interaction..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 17 (2005)
Nonlinear absorption and nonlinear refraction in ruthenium alkynyl complexes
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The studies of third-order nonlinear optical properties of organometallic compounds containing ruthenium and 'pi'-conjugated organic segments (phenylene, ethenylene, and ethynylene) is described. Our special interest has been in trigonal (octupolar) structures and in extending the structures towards dendrimers.The studies of third-order nonlinear optical properties of organometallic compounds containing ruthenium and 'pi'-conjugated organic segments (phenylene, ethenylene, and ethynylene) is described. Our special interest has been in trigonal (octupolar) structures and in extending the structures towards dendrimers. The merit of these compounds as nonlinear absorbers and for use in electrically-controlled nonlinear devices is discussed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 23 (2005)
Deformation and cleavage of microtubules studied with optical tweezers
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The mechanical properties of fluorescent microtubules (MTs) are probed with dual-optical tweezers system. The results indicate that the fluorescent MTs are much easier to be extended compared with those without fluorescence. Such MT can be extended by 30% and force for breaking up it is only several piconewtons. FurtheThe mechanical properties of fluorescent microtubules (MTs) are probed with dual-optical tweezers system. The results indicate that the fluorescent MTs are much easier to be extended compared with those without fluorescence. Such MT can be extended by 30% and force for breaking up it is only several piconewtons. Furthermore, we find that the breakup of the protofilaments is not simultaneous but step-by-step. Finally, the mechanism of the breaking is discussed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 26 (2005)
Growing process, surface morphology and nonlinear optical characteristics of vanadyl-phthalocyanine thin film fabricated on alkali halide substrate
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Nonlinear optical materials adopting optoelectronics elements are required to have a third-order nonlinear optical susceptibility of 10^(-9) order [esu]. However, the relationship between nonlinear optical characteristics and the morphology of the meal-phthalocyanine thin film prepared on alkali-halide substrate remainNonlinear optical materials adopting optoelectronics elements are required to have a third-order nonlinear optical susceptibility of 10^(-9) order [esu]. However, the relationship between nonlinear optical characteristics and the morphology of the meal-phthalocyanine thin film prepared on alkali-halide substrate remains unclear. Therefore, the growing process of vanadyl-phthalocyanine (VOPc) thin films fabricated on alkali-halide substrate were investigated by UV/Vis spectra, AFM images, and the incident angle dependence of second harmonic (SH) and third harmonic (TH) intensities measured by Marker fringe. It is recognized that VOPc thin film prepared on KBr (100) is an island-like growth, on KCl (100) it is step-terrace growth..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 28 (2005)
Experimental characterization improving the design of InGaAs/InP APD for single photon detection
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The passively quenched operation of avalanche photodiode (APD) has been used to characterizing InGaAs/InP APD including punch through voltage, avalanche voltage and break down voltage that are all important in the design of APD for single photon detection. The punch through voltage at certain doping level can be relateThe passively quenched operation of avalanche photodiode (APD) has been used to characterizing InGaAs/InP APD including punch through voltage, avalanche voltage and break down voltage that are all important in the design of APD for single photon detection. The punch through voltage at certain doping level can be related to the thickness of the InP multiplication layer and the thickness of the un-intentionally doped n-type InP layer can be adjusted in according to the experimental data. The analysis indicates that the punch through voltage should be close to the breakdown voltage that can be realized by adjusting the thickness of InP multiplication layer..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 31 (2005)
Excited state absorption and optical limiting of platinum(II) 4'-arylterpyridyl acetylide complexes
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The excited state absorption and optical limiting of a series of platinum(II) 4'-arylterpyridyl acetylide complexes have been investigated. These complexes possess relatively long triplet excited state lifetime that varies from tens of nanoseconds to several microseconds; and exhibit broad triplet excited state absThe excited state absorption and optical limiting of a series of platinum(II) 4'-arylterpyridyl acetylide complexes have been investigated. These complexes possess relatively long triplet excited state lifetime that varies from tens of nanoseconds to several microseconds; and exhibit broad triplet excited state absorption in most of the visible to near infrared spectral region. Nonlinear transmission experiments demonstrate that all of the complexes show pronounced optical limiting for ns laser pulses at 532 nm. The photophysical properties and optical limiting characteristics are influenced significantly by the nature of 4'-aryl substituent and the acetylide ligand..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 34 (2005)
Numerical study of laser-induced surface acoustic waves in different thickness pipes
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The surface acoustic waves generated by a pulsed laser in pipes are studied by using the finite element method. The time domain waveforms of guided waves in three different thickness pipes are obtained in the near field. The numerical results denoted that the excited waves by a pulsed laser in a thin-walled pipe are tyThe surface acoustic waves generated by a pulsed laser in pipes are studied by using the finite element method. The time domain waveforms of guided waves in three different thickness pipes are obtained in the near field. The numerical results denoted that the excited waves by a pulsed laser in a thin-walled pipe are typical lamb wave like in a thin plate, while in a thick pipe the main features of the surface waves are two kinds of waves: the surface skimming longitudinal wave and the Rayleigh wave, which will be useful in the applications in non-destructive evaluation of pipes..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 38 (2005)
Transient process in the triplet states of phosphorescent Ir(ppy)3 material doped in organic materials: peak shift of the emission band in polycarbonate
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Red shift of green-emission band has been observed for fac tris(2-phenylpyridine) iridium (Ir(ppy)3) doped in polycarbonate at 8 K during time evolution after 355-nm laser of 1-ns pulse width. We explain the peak shift and vibronic structure of the emission band using the Franck-Condon principle and the model of (1) thRed shift of green-emission band has been observed for fac tris(2-phenylpyridine) iridium (Ir(ppy)3) doped in polycarbonate at 8 K during time evolution after 355-nm laser of 1-ns pulse width. We explain the peak shift and vibronic structure of the emission band using the Franck-Condon principle and the model of (1) three zero-field splitting substates of the triplet state, (2) relaxation processes among the three substates, and (3) different Huang-Rhys factors for these substates. Good agreement was obtained between the calculated and measured emission spectra at various delay times..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 41 (2005)
Energy transfer between Ir(ppy)3 dopant and TPD host observed from the photoluminescence intensity and lifetime of Ir(ppy)3
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Numerical calculation has been undertaken on the temperature dependence of photoluminescence (PL) intensity and PL lifetime offac tris(2-phenylpyridine) iridium (Ir(ppy)3) phosphorescent material doped in 4,4'-bis[N-(p-tolyl)-N-phenyl-amino] biphenyl (TPD) and compared with the experimental result. Good agreement iNumerical calculation has been undertaken on the temperature dependence of photoluminescence (PL) intensity and PL lifetime offac tris(2-phenylpyridine) iridium (Ir(ppy)3) phosphorescent material doped in 4,4'-bis[N-(p-tolyl)-N-phenyl-amino] biphenyl (TPD) and compared with the experimental result. Good agreement is obtained between the observed and calculated PL intensities and lifetimes. Calculation is also made for the PL intensity and lifetime of the emission from the triplet state of TPD..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 44 (2005)
Slow and superluminal pulse propagation in temporal nonlocal response Kerr media with a CW pump
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Slow and superluminal light propagation in temporal nonlocal response Kerr media has been investigated. The group velocity, as low as tens of few centimeters per second, can be easily obtained by tuning the wavelength of a continuous-wave (CW) laser in a typical Kerr material, such as in alexandrite.Slow and superluminal light propagation in temporal nonlocal response Kerr media has been investigated. The group velocity, as low as tens of few centimeters per second, can be easily obtained by tuning the wavelength of a continuous-wave (CW) laser in a typical Kerr material, such as in alexandrite..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 47 (2005)
Synthesis and two-photon induced fluorescence spectroscopy of a novel nonlinear optical chromophore
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A novel organic chromophore (A1) is designed and synthesized with a fine structure for two-photon absorption (TPA). The single-photon induced fluorescence spectra and the fluorescence lifetime have been studied for A1, excited respectively by 297-, 355-, 422-nm laser. And the two-photon induced fluorescence spectra werA novel organic chromophore (A1) is designed and synthesized with a fine structure for two-photon absorption (TPA). The single-photon induced fluorescence spectra and the fluorescence lifetime have been studied for A1, excited respectively by 297-, 355-, 422-nm laser. And the two-photon induced fluorescence spectra were surveyed when A1 was excited by 820- and 910-nm laser. The results show that the curves of up-converted fluorescence spectra are almost same and have the same peak value at 518 nm. Accordingly, we can draw a conclusion that the TPA occurs when A1 is excited by 820- and 910-nm laser separately and though the absorption-transition pathway is different, the transition-emission pathway is the same..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 50 (2005)
Design of two-photon photochromic diarylethenes and application in 3D data storage
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A series of diarylethene derivatives with two-photon absorption was designed and synthesized. The nonlinear properties of two-photon induced fluorescence of the compounds were examined. A strategy for the design of molecules with large two-photon absorption (TRA) was developed. These compounds were also successfully apA series of diarylethene derivatives with two-photon absorption was designed and synthesized. The nonlinear properties of two-photon induced fluorescence of the compounds were examined. A strategy for the design of molecules with large two-photon absorption (TRA) was developed. These compounds were also successfully applied in two-photon three-dimensional (3D) optical data storage based on single beam two-photon femtosecond writing and one-photon fluorescence reading..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 53 (2005)
A real-coded genetic algorithm for distributed fiber Bragg grating sensor
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A real-coded genetic algorithm (RGA) for fiber Bragg grating (FBG) distributed sensing is presented. The distributed strain fields along the fiber Bragg grating sensor (FBGS) are real coded into genes, and the concept of elitism and simulated annealing are also included in this algorithm. Compared with the binary codedA real-coded genetic algorithm (RGA) for fiber Bragg grating (FBG) distributed sensing is presented. The distributed strain fields along the fiber Bragg grating sensor (FBGS) are real coded into genes, and the concept of elitism and simulated annealing are also included in this algorithm. Compared with the binary coded genetic algorithm, this method is more simple and efficient. Only with the reflect spectrum of distributed FBGS, the strain fields distribution can be exactly demodulated even in the regions with significant strain gradients. The algorithm is a promising method for demodulating the distributed FBGS, which can be used for structural failure analysis and structural damage identification..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 55 (2005)
Fabrication of Dammann gratings in silica glass
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Dammann grating is one kind of binary optical elements. We fabricated Dammann gratings in silica glass using femtosecond laser pulses at the wavelength of 800 nm with the repetition rate of 1 kHz. By using two-dimensional (2D) scanning system, we produced successfully 5*5 Dammann gratings for He-Ne laser with the wavelDammann grating is one kind of binary optical elements. We fabricated Dammann gratings in silica glass using femtosecond laser pulses at the wavelength of 800 nm with the repetition rate of 1 kHz. By using two-dimensional (2D) scanning system, we produced successfully 5*5 Dammann gratings for He-Ne laser with the wavelength of 632.8 nm. We selected suitable writing parameters to keep the length of the refractive index changed region as 160 microns across the grating. It makes the phase shift of the modulated region close to be 'pi'. The diffraction efficiency of the fabricated Dammann grating in our experiment reached to 56%, quite close to the theoretical value of 77%..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 57 (2005)
A new method for second harmonic generation
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We report a new method for second harmonic generation (SHG) by using centro-symmetric dielectric, of which 'chi'(2) is zero, rather than common nonlinear material. By designing the unique structure of centro-symmetric dielectric, which consists of two photonic crystals and several air waveguides, the efficient We report a new method for second harmonic generation (SHG) by using centro-symmetric dielectric, of which 'chi'(2) is zero, rather than common nonlinear material. By designing the unique structure of centro-symmetric dielectric, which consists of two photonic crystals and several air waveguides, the efficient second-harmonic (SH) has obtained for the sharp enhancement of the electric quadrupole polarization. Based on finite difference time domain (FDTD) algorithm, the electromagnetic field distribution in the structure and the intensity of SH along the waveguide are analyzed. When the beam intensity of the pumping wave is 1.3 MW/mm2, the conversion efficiency of power is 0.307% for a photonic crystal waveguide with a length of 40 'mu'm..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 60 (2005)
Experimental study on the depth of electric field punching through into the absorption layer of APD
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Dark-current-voltage curves and photon-current-voltage curves were measured by a passive quenched circuit so that the voltage applied to the avalanche photodiode can be much higher than breakdown voltage in study on the depth of punch through. The photo-current-voltage curve indicated clearly the punch-through voltage Dark-current-voltage curves and photon-current-voltage curves were measured by a passive quenched circuit so that the voltage applied to the avalanche photodiode can be much higher than breakdown voltage in study on the depth of punch through. The photo-current-voltage curve indicated clearly the punch-through voltage while the dark current-voltage curve is insensitive to the punch through. Furthermore, the avalanches initiated by the photo-generated carrier at a voltage lower than that from the thermo-generated carriers and explained based on the different distribution of the carriers..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 62 (2005)
Influence of the scattering phase functions on the spatially resolved reflectance spectroscopy close to the source
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The influence of the different phase functions on the spatially resolved reflectance measurements is studied with Monte Carlo simulations. We show that the spatially resolved reflectance from a homogenous semi-infinite medium is mostly dependent on the second-order factor of tissue except for the absorption coefficientThe influence of the different phase functions on the spatially resolved reflectance measurements is studied with Monte Carlo simulations. We show that the spatially resolved reflectance from a homogenous semi-infinite medium is mostly dependent on the second-order factor of tissue except for the absorption coefficient, the reduced scattering coefficient and the refractive index at short source-detector separations. However, the effect of the high-order-factors is very weaker. Then we analyze the given conclusion and find that the parameter varies with the same current following the first-order moment for the phase functions containing two parameters..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 65 (2005)
Pyroelectric activity in polar hemicyanine Langmuir-Blodgett multilayer films
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The Langmuir-Blodgett (LB) films of hemicyanine dyes were prepared by LB technique. The films showed pyroelectric effect. The pyroelectric coefficient measured by the method of integrated charges was 12 'mu'C/(m2K) at room temperature, and the relationship between the orientation of DAEP dye in the films and teThe Langmuir-Blodgett (LB) films of hemicyanine dyes were prepared by LB technique. The films showed pyroelectric effect. The pyroelectric coefficient measured by the method of integrated charges was 12 'mu'C/(m2K) at room temperature, and the relationship between the orientation of DAEP dye in the films and temperature was studied by polarized Fourier transform infrared spectroscopy (FTIR) spectroscopy and second harmonic generation (SHG). It was indicated that the observed pyroelectricity can be ascribed preliminarily to the structure modification of the polar head groups and the deterioration of the film framework (the first-order phase transition) resulted in the change of spontaneous polarization with temperature..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 68 (2005)
Development of far field and near field optical trapping
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Optical trapping is an increasingly important technique for manipulating and probing matter ranging from nanometers to millimeters. In this paper, the theories of optical trapping to date are reviewed briefly. The typical conventional far field trapping design is introduced. A 5-micron yeast cell is trapped and manipulOptical trapping is an increasingly important technique for manipulating and probing matter ranging from nanometers to millimeters. In this paper, the theories of optical trapping to date are reviewed briefly. The typical conventional far field trapping design is introduced. A 5-micron yeast cell is trapped and manipulated with a 1.25 numerical aperture (NA) oil-immersion, 100X magnification objective by a 780 nm trapping beam at 16 mW in our experiment. Furthermore, the development of near-field optical trapping associated with evanescent wave is also discussed. Several proposed near-field trapping schemes, respectively using laser-illuminated metal tip, metal-coated fiber probe in the scanning near-field optical microscopy (SNOM) and focused evanescent wave, are also described..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 71 (2005)
Transmission properties of terahertz radiation through a single sub-wavelength circular hole in the metal foil
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The terahertz (THz) transmission properties of a single sub-wavelength circular hole in the free-standing metal foil are experimentally investigated. A THz time-domain spectroscopy (THz-TDS) is utilized to measure the transmission coefficient from 0.2 to 2.2 THz. The transmission coefficients for the aperture with diffThe terahertz (THz) transmission properties of a single sub-wavelength circular hole in the free-standing metal foil are experimentally investigated. A THz time-domain spectroscopy (THz-TDS) is utilized to measure the transmission coefficient from 0.2 to 2.2 THz. The transmission coefficients for the aperture with different diameters ranging from d=150 to 500 microns are presented. The results indicate that the samples change the temporal and spectral characteristics of the incident THz pulses. In particular, there is a remarkable stop band for d=150 microns in the transmission spectrum which the conventional diffraction theory cannot explain. Further theoretical analysis is necessary..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 74 (2005)
Study on the second-order nonlinear optical characteristics of urea L-malic acid
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The second-order nonlinear optical characteristics of a novel organic crystal, urea L-malic acid (ULMA), were studied. Both type I and type II phase-matching angles of the biaxial crystal ULMA were calculated, whose loci are in the Hobden class 9. The efficiencies of second harmonic generation (SHG) of ULMA and KDP at The second-order nonlinear optical characteristics of a novel organic crystal, urea L-malic acid (ULMA), were studied. Both type I and type II phase-matching angles of the biaxial crystal ULMA were calculated, whose loci are in the Hobden class 9. The efficiencies of second harmonic generation (SHG) of ULMA and KDP at a fundamental wavelength of 1064 nm were compared by using the Kurtz powder method. The results showed that the nonlinear coefficient of ULMA is about 1.57 times of that of KDP. High SHG efficiencies were observed over a broad range of the spectrum when ULMA was pumped by outputs generated from an optical parameter oscillator. To our knowledge, it is the first report where continuous SHG at fundamental wavelengths from 1300 to 950 nm with ULMA was achieved..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 77 (2005)
Fabrication of fused silica phase gratings with inductively coupled plasma technology
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Inductively coupled plasma (ICP) technology is a new advanced version of dry-etching technology compared with the widely used method of reactive ion etching (RIE). Plasma processing of the ICP technology is complicated due to the mixed reactions among discharge physics, chemistry and surface chemistry. Extensive experiInductively coupled plasma (ICP) technology is a new advanced version of dry-etching technology compared with the widely used method of reactive ion etching (RIE). Plasma processing of the ICP technology is complicated due to the mixed reactions among discharge physics, chemistry and surface chemistry. Extensive experiments have been done and microoptical elements have been fabricated successfully, which proved that the ICP technology is very effective in dry etching of microoptical elements. In this paper, we present the detailed fabrication of microoptical fused silica phase gratings with ICP technology. Optimized condition has been found to control the etching process of ICP technology and to improve the etching quality of microoptical elements greatly. With the optimized condition, we have fabricated lots of good gratings with different periods, depths, and duty cycles. The fabricated gratings are very useful in fields such as spectrometer, high-efficient filter in wavelength-division-multiplexing system, etc...
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 79 (2005)
Microoptical research in Shanghai Institute of Optics and Fine Mechanics
This paper summarized the recent research results of Changhe Zhou's group of Information Optics Lab in Shanghai Institute of Optics and Fine Mechanics (SIOM). The first is about the Talbot self-imaging research. We have found the symmetry rule, the regular-rearranged neighboring phase difference rule and the prime-This paper summarized the recent research results of Changhe Zhou's group of Information Optics Lab in Shanghai Institute of Optics and Fine Mechanics (SIOM). The first is about the Talbot self-imaging research. We have found the symmetry rule, the regular-rearranged neighboring phase difference rule and the prime-number decamping rule, which is briefly summarized in a recent educational publication of Optics and Photonics News, pp.46-50, November 2004. The second is about four novel microoptical gratings designed and fabricated in SIOM. The third is about the design and fabrication of novel supperresolution phase plates for beam shaping and possible use in optical storage. The fourth is to develop novel femtosecond laser information processing techniques by incorporating microoptical elements, for example, use of a pair of reflective Dammann gratings for splitting the femtosecond laser pulses. The most attractive feature of this approach is that the conventional beam splitter is avoided. The conventional beam splitter would introduce the unequal dispersion due to the broadband spectrum of ultrashort laser pulses, which will affect the splitting result. We implemented the Dammann splitting apparatus by using two-layered reflective Dammann gratings, which generates the almost same array without angular dispersion. We believe that our device is highly interesting for splitting femtosecond laser pulses..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 82 (2005)
Micro-photodiode arrays as artificial retina implant
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This paper describes a photoelectric device that is intended to serve as a replacement for degenerated photoreceptor cells in the retina. The device is a kind of silicon based micro-photodiode arrays. The final implant devices were approximately 100 microns in thickness and ranged in diameter from 2.5 to 3.5 mm. The inThis paper describes a photoelectric device that is intended to serve as a replacement for degenerated photoreceptor cells in the retina. The device is a kind of silicon based micro-photodiode arrays. The final implant devices were approximately 100 microns in thickness and ranged in diameter from 2.5 to 3.5 mm. The individual photodiode subunits on the device is approximately 250*250 (micron) and the isolated channel between these subunits is about 50-micron width. The implant feasibility of device was tested in vivo and in vitro. The results show that the device has good biocompatibility. When it was implanted into rabbits and powered by light, visual evoked potential (VEP) can be induced..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 84 (2005)
Experimental demonstration of the wideband double-pass discrete Raman amplifiers based on a gold-film reflector
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We experimentally demonstrate a wideband double-pass discrete Raman amplifier using a gold-film. In this Raman amplifier (RA), by using a one-end gilded fiber as the broadband reflector, signals and multi-pump are simultaneously reflected to propagate through the gain fiber for a second time in the opposite direction oWe experimentally demonstrate a wideband double-pass discrete Raman amplifier using a gold-film. In this Raman amplifier (RA), by using a one-end gilded fiber as the broadband reflector, signals and multi-pump are simultaneously reflected to propagate through the gain fiber for a second time in the opposite direction of the input. An increase in net gain of more than 150% has been achieved compared with that in the typical co-pumped Raman amplifier. The noise and polarization dependent gain (PDG) characteristics of such a RA are also investigated..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 86 (2005)
Experimental study on the fluorescence lifetime of ethanol-water mixtures
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The ethanol-water mixtures can emit fluorescence when excited by the ultraviolet (UV) light, which is different from pure ethanol and water. There are three emission bands of the mixtures and the center bands are located at 290, 305, and 330 nm, respectively. The fluorescence lifetimes of different emission bands are tThe ethanol-water mixtures can emit fluorescence when excited by the ultraviolet (UV) light, which is different from pure ethanol and water. There are three emission bands of the mixtures and the center bands are located at 290, 305, and 330 nm, respectively. The fluorescence lifetimes of different emission bands are tested respectively: the average lifetime of 330-nm fluorescence band is about 26.5 ns, for the 305-nm emission band 2.5 ns, and for the 290-nm band 11 ns. By the spectral characteristic and the time-resolved spectroscopy one can conclude that there are several components in the solution of ethanol-water mixture..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 88 (2005)
Possible correlation between second-order dispersion and glucose concentration investigated by low time-coherence interferometry
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A possible correlation between second-order dispersion and glucose concentration is presented for the first time. The second-order dispersions of three different glucose concentrations: hypoglycemia, normal level, and hyperglycemia are analyzed over the wavelength range from 0.55 to 0.8 micron by Fourier analysis of thA possible correlation between second-order dispersion and glucose concentration is presented for the first time. The second-order dispersions of three different glucose concentrations: hypoglycemia, normal level, and hyperglycemia are analyzed over the wavelength range from 0.55 to 0.8 micron by Fourier analysis of the interferogram. The preliminary correlation between second-order dispersion and glucose concentration is investigated by linear fitting the second-order dispersion from 0.65 to 0.75 micron. This correlation is expected to determine the different glucose concentrations by measuring the second-order dispersion, which can be considered as a potentially noninvasive method to measure glucose concentration in human eye..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 91 (2005)
A new approach to mass fabrication technology of microstructured polymer optical fiber preform
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We have successfully fabricated microstructured polymer optical fiber (MPOF) preforms by polymerization method of monomer and thermo-melting-extrusion of PMMA grains in home-made mould. Monomer-based fabrication of MPOF preform offers key advantages over both conventional capillaries stack-draw and drill-machining methWe have successfully fabricated microstructured polymer optical fiber (MPOF) preforms by polymerization method of monomer and thermo-melting-extrusion of PMMA grains in home-made mould. Monomer-based fabrication of MPOF preform offers key advantages over both conventional capillaries stack-draw and drill-machining methods. By varying structure of the mould, it is easy to make different cross-section preforms of speciality fibers with holes of arbitrary shapes and sizes in any desired arrangement. We have also exploited preparation method of MPOF preforms with chemical doping or modification of the polymer itself, and successfully incorporated laser dyes, rhodamines into core of MPOF preform..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 94 (2005)
Performance improvement of a supercontinuum continuous-wave optical source
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We have studied the influence of degenerate four wave mixing (FWM) on the performance of the multiwavelength continuous-wave (CW) optical source based on supercontinuum (SC). By suppressing degenerate FWM, a 100-channel SC CW optical source with 25-GHz spacing for 10-Gb/s dense wavelength division multiplexing (DWDM) sWe have studied the influence of degenerate four wave mixing (FWM) on the performance of the multiwavelength continuous-wave (CW) optical source based on supercontinuum (SC). By suppressing degenerate FWM, a 100-channel SC CW optical source with 25-GHz spacing for 10-Gb/s dense wavelength division multiplexing (DWDM) systems is experimentally demonstrated. Confirmation is provided with the generation of CW channel with crosstalk of other channels less than -28 dB and the presentation of 10-Gb/s eye diagram and bit error rate (BER) performance..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 96 (2005)
Numerical simulation for laser-induced breakdown thresholds and plasma formation in water
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Two models to calculate the irradiance threshold for laser-induced breakdown for water have been introduced. Both of the models have been incorporated into a computer code and code results compared to experimentally measured irradiance threshold for breakdown of pure water by nanosecond, picosecond and femtosecond laseTwo models to calculate the irradiance threshold for laser-induced breakdown for water have been introduced. Both of the models have been incorporated into a computer code and code results compared to experimentally measured irradiance threshold for breakdown of pure water by nanosecond, picosecond and femtosecond laser pulses in the visible and near-infrared. The result shows that the second one has a wider range than first one to agree with the experiment data. For nanosecond laser pulses, the generation of free electrons in distilled water is initiated by multiphoton ionization but then dominated by cascade ionization. For shorter laser pulses, multiphoton ionization gains ever more importance, and collision and recombination losses during breakdown diminish. The threshold near infrared is more depend on the initial electrons..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 100 (2005)
Numerical simulation of laser-induced plasma expansion in air
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A numerical study of the expansion of a laser-induced plasma is given by using of techniques of computational fluid dynamics. According to the experiment results reported, the density of electrons is assembled on the surface of the ionization area. In the present simulation, the model is considered as an expansion of pA numerical study of the expansion of a laser-induced plasma is given by using of techniques of computational fluid dynamics. According to the experiment results reported, the density of electrons is assembled on the surface of the ionization area. In the present simulation, the model is considered as an expansion of plasma bubble in air. The laser energy is absorbed by the surface of the plasma bubble facing to the laser beam. Numerical results show the elongation of the bubble along the laser beam direction, which agrees with the experiments..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 103 (2005)
Area-selective deposition of self-assembled monolayers on a synchrotron radiation etching pattern
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Patterning of self-assembled monolayer (SAM) was demonstrated by area-selective deposition of SAMs on a pattern made by synchrotron radiation (SR) stimulated etching SiO2 thin films. The etching was conducted by exposing the SiO2 films to SR through a Co contact mask with SF6+O2 as the reaction gas. A dodecene SAM was Patterning of self-assembled monolayer (SAM) was demonstrated by area-selective deposition of SAMs on a pattern made by synchrotron radiation (SR) stimulated etching SiO2 thin films. The etching was conducted by exposing the SiO2 films to SR through a Co contact mask with SF6+O2 as the reaction gas. A dodecene SAM was deposited on the etched surface and an octadecyltrichlorosilane SAM was deposited on the SiO2 surface. The deposited SAMs were densely packed and well ordered, which were characterized by infrared spectroscopy, ellipsometer, and water contact angle..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 106 (2005)
Serial and parallel arrangements of NOLM and NALM loop mirrors
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We present the switching equations for the nonlinear optical loop mirror (NOLM), for two NOLM loops in series, for two NOLM loops in parallel, for the nonlinear amplifying loop mirror (NALM), for two NALM loops in series, and for two NALM loops in parallel. We investigate the switching behavior of arrangements of two iWe present the switching equations for the nonlinear optical loop mirror (NOLM), for two NOLM loops in series, for two NOLM loops in parallel, for the nonlinear amplifying loop mirror (NALM), for two NALM loops in series, and for two NALM loops in parallel. We investigate the switching behavior of arrangements of two identical and two different NOLM loops in dependence of the length of the nonlinear Kerr fiber, the effective fiber core area and the coupling constant. The same investigations are carried out with two identical and two different NALM loops, where additional the dependence of the gain is considered. The coupling constant 'alpha' is kept fixed at 0.5..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 109 (2005)
Coherence measurement of a Ti:sapphire femtosecond pulsed laser
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The interference patterns produced by Gaussian-shaped broad-bandwidth femtosecond pulsed laser sources are derived. The interference pattern contains both spatial and temporal properties of laser beam. Interference intensity dependent on the bandwidth of femtosecond laser are given. We demonstrate experimentally both tThe interference patterns produced by Gaussian-shaped broad-bandwidth femtosecond pulsed laser sources are derived. The interference pattern contains both spatial and temporal properties of laser beam. Interference intensity dependent on the bandwidth of femtosecond laser are given. We demonstrate experimentally both the spatial and the temporal coherence properties of a Ti:sapphire femtosecond pulse laser, as well as its power spectrum by using a pinhole pair..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 115 (2005)
Time-resolved terahertz spectroscopy of explosive materials
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We studied terahertz spectra of hexanitrohexaazaisowurtzitane ('varepsilon'-HNIW and 'gamma'-HNIW), a kind of explosive materials, using terahertz time-domain spectroscopy (THz-TDS) in the 0.2-2.5 THz region. The experimental results show that explosive samples with different conformations have differenWe studied terahertz spectra of hexanitrohexaazaisowurtzitane ('varepsilon'-HNIW and 'gamma'-HNIW), a kind of explosive materials, using terahertz time-domain spectroscopy (THz-TDS) in the 0.2-2.5 THz region. The experimental results show that explosive samples with different conformations have different intermolecular or phonon bands. For 'varepsilon'-HNIW, the observed absorption peaks were located at 0.99, 1.32, 1.43, and 2.08 THz; for 'gamma'-HNIW, the absorption peaks were observed at 1.05, 1.52, and 1.90 THz. The frequency dependent refraction index and absorption coefficients of two samples were also extracted..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 117 (2005)
Application of single chip processor in an interrogating system for fiber Bragg grating sensors with a fiber Fabry-Perot wavelength filter
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A novel interrogation system for fiber Bragg grating (FBG) sensors with a tunable fiber Fabry-Perot (FFP) wavelength filter is proposed. The system combines a feedback loop arrangement and micro control unit (MCU), which integrates the closed-loop tracking mode into the scanning mode by varying the process of sawtooth A novel interrogation system for fiber Bragg grating (FBG) sensors with a tunable fiber Fabry-Perot (FFP) wavelength filter is proposed. The system combines a feedback loop arrangement and micro control unit (MCU), which integrates the closed-loop tracking mode into the scanning mode by varying the process of sawtooth voltage. As a result, the wavelengths of fiber grating sensor arrays can be interrogated; moreover, the wavelength of arbitrary FBG under dynamic conditions in the arrays can be tracked and then be locked. A strain resolution of <0.3-ustrain can be realized using this system..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 120 (2005)
Experimental study of the FemtoTalbot effect
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Experimental investigation of Talbot self-imaging effect of an amplitude grating under illumination of femtosecond laser pulse -- the FemtoTalbot effect is reported. Theoretical analyzed results show that Talbot images under illumination of femtosecond laser pulses are not the same as that under continuous wave illuminExperimental investigation of Talbot self-imaging effect of an amplitude grating under illumination of femtosecond laser pulse -- the FemtoTalbot effect is reported. Theoretical analyzed results show that Talbot images under illumination of femtosecond laser pulses are not the same as that under continuous wave illumination. Experimental results are in good agreement with the theoretical analysis. We believe that the experimental investigation of the FemtoTalbot effect is highly interesting for the enormous potential applications of Talbot effect..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 122 (2005)
Second-order nonlinear optical properties of centrosymmetric nanoparticles studied by hyper-Rayleigh scattering (HRS) technique
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Hyper-Rayleigh scattering (HRS) technique has been used to study second-order nonlinear optical (NLO) properties of some centrosymmetric metal and semiconductor nanoparticles. All the samples display big "per particle" first hyperpolarizabilities 'beta'~~(par). For centrosymmetric particles the contriHyper-Rayleigh scattering (HRS) technique has been used to study second-order nonlinear optical (NLO) properties of some centrosymmetric metal and semiconductor nanoparticles. All the samples display big "per particle" first hyperpolarizabilities 'beta'_(par). For centrosymmetric particles the contributions of multipolar radiations are very important to their second-order NLO responses. The metal nanoparticles show 'beta'_(par) two orders greater than that of the semiconductor ones, which can be explained by the enhancement of surface plasma resonance (SPR). It also reveals that the HRS signals are very sensitive to metal nanoparticles' aggregation..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 125 (2005)
First hyperpolarizabilities of several azobenzene derivatives studied by hyper-Rayleigh scattering (HRS)
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The first hyperpolarizabilities ('beta') of four azobenzene derivatives are measured via hyper-Rayleigh scattering (HRS) technique at 1064 nm. These compounds show weak absorbance at 532 nm and neglectable two-photon fluorescence (TPF). Their static first hyperpolarizabilities ('beta0') are estimated byThe first hyperpolarizabilities ('beta') of four azobenzene derivatives are measured via hyper-Rayleigh scattering (HRS) technique at 1064 nm. These compounds show weak absorbance at 532 nm and neglectable two-photon fluorescence (TPF). Their static first hyperpolarizabilities ('beta0') are estimated by the classical two-level model. The effects of varying the variety and number of the acceptors from chloro to nitro substituents are studied. It is concluded that the first hyperpolarizabilities will be enhanced with increasing polarity or number of the acceptors, attributed to improved transferability of their 'pi'-conjugated electron clouds..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 128 (2005)
Broadband parametric amplification in ultrafast fluorescence application
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Broadband parametric amplification is applied for the femtosecond ultrafast fluorescence research. The time resolution depends on duration of pump pulse, which works both as pump source and gate. For spectrum application, a special phase-matching angle exists for broadband amplification correspondence to the pump wavelBroadband parametric amplification is applied for the femtosecond ultrafast fluorescence research. The time resolution depends on duration of pump pulse, which works both as pump source and gate. For spectrum application, a special phase-matching angle exists for broadband amplification correspondence to the pump wavelength. The broadband amplification range from 500 to 750 nm was found for 'beta'-barium borate (BBO) crystal, pumped at 400 nm. Large dye fluorescence amplification of 10^(7) is realized. The generation of cone emission is selected as reference for system tuning. It is supposed to be a new method for ultrafast study in fluorescence comparable to fluorescence up-conversion and optical Kerr gate techniques..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 131 (2005)
Photon state-vector function
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The exclusive carrier of photonics is photon, which is a kind of microscopic particles so that obeys the generalized Schrodinger equation, namely the motion equation for a photon. A novel state-vector function that satisfies the equation with three quantum conditions has been constructed, which possesses not only the eThe exclusive carrier of photonics is photon, which is a kind of microscopic particles so that obeys the generalized Schrodinger equation, namely the motion equation for a photon. A novel state-vector function that satisfies the equation with three quantum conditions has been constructed, which possesses not only the energy and the momentum but also the angular momentum (spin) for a photon. The analyses of the state-vector function indicate that the macroscopic polarization of light is how to relate with microscopic parameters of a photon such as the probability amplitude and the phase..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 134 (2005)
Nondegenerate four-wave mixing participated by two-photon excited stimulated emission
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Two-photon excited stimulated emission at ~617 nm has been achieved in an organic chromophore solution pumped at 1064 nm. The stimulated emission can be observed only in the forward and backward directions and is characterized by its high directionality and spectral narrowing. The solution was illuminated simultaneouslTwo-photon excited stimulated emission at ~617 nm has been achieved in an organic chromophore solution pumped at 1064 nm. The stimulated emission can be observed only in the forward and backward directions and is characterized by its high directionality and spectral narrowing. The solution was illuminated simultaneously with a strong 1064-nm pump beam and a 1064-nm weak signal beam to form an induced Bragg grating. As the strong pump beam itself induced the backward two-photon excited stimulated emission, which was a reading beam, we observed backward nondegenerate four-wave mixing (NFWM). The newly generated wave by the NFWM has the same frequency as the reading beam. Due to the phase mismatching, this newly generated coherent wave was not exactly counter-propagating to the signal wave..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 136 (2005)
Spectral characteristics of cladding index modulated fiber grating
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A new class of fiber grating with only cladding index modulation is presented and analyzed theoretically. The calculation of the modes involved in this paper is based on a model of three-layer step-index fiber geometry. The transmission of a mode guided by the core through a cladding index modulated grating when evanesA new class of fiber grating with only cladding index modulation is presented and analyzed theoretically. The calculation of the modes involved in this paper is based on a model of three-layer step-index fiber geometry. The transmission of a mode guided by the core through a cladding index modulated grating when evanescent field coupling occurs is analyzed with couple-mode theory. Lower attenuation and flexible spectral characteristics can be obtained in comparison with traditional fiber core index modulated grating..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 138 (2005)
High-efficiency diffraction gratings in fused silica at the wavelength of 632.8 nm
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We describe high-efficiency diffraction gratings fabricated in fused silica at the wavelength of 632.8 nm by rigorous coupled-wave analysis (RCWA). High-density holographic gratings, if the groove density falls within the range of 1575-1630 lines/mm and the groove depth within the range of 1.1-1.3 microns, can realize We describe high-efficiency diffraction gratings fabricated in fused silica at the wavelength of 632.8 nm by rigorous coupled-wave analysis (RCWA). High-density holographic gratings, if the groove density falls within the range of 1575-1630 lines/mm and the groove depth within the range of 1.1-1.3 microns, can realize high diffraction efficiencies at the wavelength of 632.8 nm, e.g., the first Bragg diffraction efficiency can theoretically achieve more than 93% both in TE- and TM-polarized incidences, which greatly reduces the polarization-dependent losses. Note that with different groove profiles further optimized, the maximum efficiency of more than 99.69% can be achieved for TM-polarized incidence, or 97.81% for TE-polarized incidence..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 141 (2005)
Confocal microscopy of FM 4-64 tagged membranes in the living fungus Trichoderma reesei
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Visualization of the protein secretory pathway in the high secreting trichoderma reesei (T. reesei) hyphae using confocal microscopy will lead to better understanding of the cellular mechanisms involved in protein secretion and contribute to the identification of bottlenecks in the secretion of foreign proteins from fuVisualization of the protein secretory pathway in the high secreting trichoderma reesei (T. reesei) hyphae using confocal microscopy will lead to better understanding of the cellular mechanisms involved in protein secretion and contribute to the identification of bottlenecks in the secretion of foreign proteins from fungi. An introduction into visualization approaches involved the application of the fluorescent dye FM 4-64 for staining of membrane-based structures in T. reesei hyphae. Confocal microscopy studies were carried out with 24-hour old cultures of the T. reesei strain Rut-C30. Staining of the fungal hyphae and characteristics of FM 4-64 including spectral properties, time course of the labeling and double labeling with other specific organelle dyes will be discussed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 143 (2005)
Light propagation in ocular tissue with femtosecond oscillator at 800-nm wavelength
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Currently, lasers are widely used in biomedical field for both diagnoses and treatment. At the same time, new laser techniques are investigated to improve the application efficiency. Due to its ultrashort pulse duration and high pulse intensity, femtosecond laser shows distinctive advantages over long pulse lasers. SinCurrently, lasers are widely used in biomedical field for both diagnoses and treatment. At the same time, new laser techniques are investigated to improve the application efficiency. Due to its ultrashort pulse duration and high pulse intensity, femtosecond laser shows distinctive advantages over long pulse lasers. Since the characteristics of light propagation in ocular medium are basic concern for laser application in ophthalmology, in our research, light propagation in some ocular tissues was investigated. The samples were from fresh pig eyes. The laser source was femtosecond oscillator system at 800-nm wavelength. The linear and nonlinear phenomena during laser propagation in ocular medium were discussed. Without using chirped pulse amplification system, femtosecond oscillator system itself provides a low energy processing. Our experimental results suggest that the femtosecond oscillator system has a potential to ensure the precision of incision and minimize the collateral damage in glaucoma treatment..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 147 (2005)
Photobiomodulation as a cellular model of traditional Chinese medicine
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Yin-yang concepts of traditional Chinese medicine (TCM) for TCM objects such as whole body, five zangs or six fus are widely used to discuss cellular processes. In this paper, the concept of the degree of difficulty (DD) of a process was put forward to redefine yin and yang and extend TCM yin-yang model to DD yin-yang Yin-yang concepts of traditional Chinese medicine (TCM) for TCM objects such as whole body, five zangs or six fus are widely used to discuss cellular processes. In this paper, the concept of the degree of difficulty (DD) of a process was put forward to redefine yin and yang and extend TCM yin-yang model to DD yin-yang model. It was shown that healthy cells are in DD yin ping yang mi so that there is no photobiomodulation, and there is photobiomodulation on non-healthy cells until the cells become healthy so that photobiomodulation can be called cellular rehabilitation..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 150 (2005)
Spectral analysis of abnormal liver tissue using fluorescence and Raman spectroscopy
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In this paper, laser induced human serum Raman spectra of liver cancer are measured. The differences in serum spectra between normal people and liver cancer patients are analyzed. For the typical spectrum of normal serum, there are three sharp Raman peaks and relative intensity of Raman peaks excited by 514.5 nm is higIn this paper, laser induced human serum Raman spectra of liver cancer are measured. The differences in serum spectra between normal people and liver cancer patients are analyzed. For the typical spectrum of normal serum, there are three sharp Raman peaks and relative intensity of Raman peaks excited by 514.5 nm is higher than that excited by 488.0 nm. However, for the Raman spectrum of liver cancer serum there are no peaks or very weak Raman peaks at the same positions. To liver cirrhosis, the shape of Raman peak is similar to normal and fluorescence spectrum is similar to that of liver cancer from statistic data. Moreover, the liver fibrosis and liver cirrhosis were studied using the technology of laser-induced fluorescence (LIF). The experiment indicates that the blue shift of fluorescence peak differences between the normal, liver fibrosis and liver cirrhosis were observed. These results have important reference values to explore the method of laser spectrum diagnosis..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 153 (2005)
Effects of layer structure of the skin on the measured signal by optical coherence tomography
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Optical coherence tomography (OCT) is a noninvasive cross-sectional imaging modality capable of measuring tissue morphology and function with high spatial resolution. Both the amplitude and the phase of the interometric heterodyne signal can be exploited to obtain the profile of sample reflectivity related to its microOptical coherence tomography (OCT) is a noninvasive cross-sectional imaging modality capable of measuring tissue morphology and function with high spatial resolution. Both the amplitude and the phase of the interometric heterodyne signal can be exploited to obtain the profile of sample reflectivity related to its microstructure and the bi-directional blood flowing velocity information. The fact that the skin and human mucosa have a layer structure suggests that the backscattered signal from tissue arises from two sources. The first is the scattering particles within the tissue. The second is the Fresnel refraction on the interface between two layers. However, the analysis available only considers one aspect of the backscattering sources. In this paper, we report an analysis that is based on the combination of both the particle scattering within the tissue and the Fresnel reflection on the interfaces between two layers. The new model is more reasonable for establishing the relationship between the signal detected by OCT scanner and tissue structures..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 156 (2005)
Photobiomodulation on delayed onset muscle soreness
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If the radiation intensity is so low that the photodynamic effects of endogenous photosensitizers can not damage membrane or cell compartments, there would be photobiomodulation on delayed onset muscle soreness (DOMS) at the radiation dose chosen according to the biological information model of photobiomodulation sinceIf the radiation intensity is so low that the photodynamic effects of endogenous photosensitizers can not damage membrane or cell compartments, there would be photobiomodulation on delayed onset muscle soreness (DOMS) at the radiation dose chosen according to the biological information model of photobiomodulation since the intracellular proteolysis of damaged proteins by ubiquitin-proteasome pathway should be the key process for DOMS recovery..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 159 (2005)
Application of surface enhanced Raman scattering spectroscopy in rat serum
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High signal-to-noise surface enhanced Raman scattering (SERS) signal of rat serum was obtained in this article. Two methods were presented to enhance the intensity of rat serum SERS signal. The novel colloid silver was synthesized using heating method by microwave and it was introduced to be the active site of SERS, &qHigh signal-to-noise surface enhanced Raman scattering (SERS) signal of rat serum was obtained in this article. Two methods were presented to enhance the intensity of rat serum SERS signal. The novel colloid silver was synthesized using heating method by microwave and it was introduced to be the active site of SERS, "hot sites" could be detected in the active site. At same time the high numerical aperture (NA) oil immersed object lens was applied in micro-Raman system so that some new peaks come up in SERS spectrum of rat serum because of the evanescent wave was employed to excite the sample..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 161 (2005)
Analysis of the effects of intraocular lens edge design on dysphotopsia for pseudophakic patients
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The dysphotopia that is connected to the reflection of light from the intraocular lens (IOL) edge is analyzed. A new IOL with 'Sigma' edge is investigated, and other three IOLs are also studied for comparison. The interaction of rays as a function of edge design was evaluated in an experimental model of the pseThe dysphotopia that is connected to the reflection of light from the intraocular lens (IOL) edge is analyzed. A new IOL with 'Sigma' edge is investigated, and other three IOLs are also studied for comparison. The interaction of rays as a function of edge design was evaluated in an experimental model of the pseudophakic eye using the ray-tracing program of ZEMAX software (Focus Software, Inc.). The results show the rays crossing the edges of IOLs form an image with the shape of a partial ring or thin arc in the periphery of the retina, the potential of the 'Sigma' edge to lower dysphotopsia for pseudophakic patients is promising..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 164 (2005)
In vivo measurement of absorption coefficient in rat brain and statistic analysis
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A specific designed steady-state fiber spectrometer system was applied to measure the optical parameters in rat brain tissue. The reduced scattering coefficient spectrum was obtained from the responding empirical formula, while the absorption coefficient spectrum can be fitted by a unique diffusion theoretical model inA specific designed steady-state fiber spectrometer system was applied to measure the optical parameters in rat brain tissue. The reduced scattering coefficient spectrum was obtained from the responding empirical formula, while the absorption coefficient spectrum can be fitted by a unique diffusion theoretical model in near infrared range (650-850 nm). 12 rats were performed in vivo in real time measurements. The range of absorption coefficient in gray matter and white matter of rat brain tissue were obtained from the systemic statistic analysis by applying the empirical formula and theoretical model, and the results were evaluated by tissue phantom experiment. These data have great value in research and clinic applications..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 167 (2005)
Human infrared thermal imaging technology and its clinical applications
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With improvements in infrared camera technology and the promise of reduced costs and noninvasive character, infrared thermal imaging resurges in medicine. The skin temperature distribution of a healthy human body exhibits a contralateral symmetry. Any disease inside body is associated with an alteration of the thermal With improvements in infrared camera technology and the promise of reduced costs and noninvasive character, infrared thermal imaging resurges in medicine. The skin temperature distribution of a healthy human body exhibits a contralateral symmetry. Any disease inside body is associated with an alteration of the thermal distribution of human body. So human thermography is of unique value in studying the physiology of thermoregulation, diagnosing some diseases or evaluating the situation of human health. The physical principle of human thermography and its clinical applications are dicsussed. The latest progress of thermography, thermal texture maps (TTM) and its effectiveness are introduced..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 170 (2005)
Fluorescence detection system and laminate-based disposable microfluidic chip
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Development of a compact fluorescence point-of-care system (POCS) is challenging. A prototype of compact fluorescence detection system and disposable microfluidic chip reported in this letter used a blue LED, 600-micron fiber, CCD detector, mylar and polymethyl-methacrylate (PMMA), and fluorescein solution as an excitaDevelopment of a compact fluorescence point-of-care system (POCS) is challenging. A prototype of compact fluorescence detection system and disposable microfluidic chip reported in this letter used a blue LED, 600-micron fiber, CCD detector, mylar and polymethyl-methacrylate (PMMA), and fluorescein solution as an excitation source, light-guide, detector, microfluidic chip substrates and samples, respectively. The results show the system is able to detect 0.01-1000 micro-g/l fluorescein in tris buffered saline pH 8.0 and gives linear response. This prototype can be used as a platform to develop a simple and compact multichannel-fluorescence point-of-care bioassay system with an inexpensive and disposable microfluidic chip..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 173 (2005)
Detection and characterization of esophagus dysplasia using fluorescence and Raman spectroscopy
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In this paper, we present a three-parametric model using Raman and fluorescence spectroscopy for detection and analysis of esophagus dysphasia and esophagus cancer. The model was set up from more than 1000 samples. And 56 samples were used to test this algorithm of the model prospectively. The serum spectra were exciteIn this paper, we present a three-parametric model using Raman and fluorescence spectroscopy for detection and analysis of esophagus dysphasia and esophagus cancer. The model was set up from more than 1000 samples. And 56 samples were used to test this algorithm of the model prospectively. The serum spectra were excited by laser of the wavelengths 488.0 and 514.5 nm. The apparent differences of auto-fluorescence and Raman spectroscopy were observed for patients compared to the normal: the majority of the fluorescence spectra did not have violent alteration, but three Raman peaks disappeared or were found to be very weak. Moreover, 'Delta lambda' value (red shift of fluorescence peak) and 'alpha'-value (rate of fluorescence intensity) also provide the reference for future research. And I-value (intensity of Raman peak) will decrease with progression of the tumor. The result of spectral analysis is accordance with the clinical diagnosis..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 176 (2005)
Comparison of tumor vascular blood volume measured by near infrared spectroscopy and 19F NMR spectroscopy
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Near-infrared spectroscopy (NIRS) was used to measure changes of total hemoglobin concentration, 'Delta'(Hb)~~(total), and relative vascular oxygenation 'Delta'(HbO2) in rat mammary and prostate tumors in response to hyperoxic gas interventions. 19F NMR of vascular perflubron was used to compare with thNear-infrared spectroscopy (NIRS) was used to measure changes of total hemoglobin concentration, 'Delta'(Hb)_(total), and relative vascular oxygenation 'Delta'(HbO2) in rat mammary and prostate tumors in response to hyperoxic gas interventions. 19F NMR of vascular perflubron was used to compare with the NIRS observations. The consistent trends between 'Delta'(Hb)_(total) and 'Delta'V_(T-blood) demonstrated that the NIRS can serve as an accurate, non-invasive, real time, monitoring tool for tumor vascular volume measurement. Meanwhile, these results also demonstrated that different types of tumors may respond to hyperoxic gases differently, and that NIRS could be used to assess vascular oxygenation changes non-invasively for guiding tumor therapy..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 179 (2005)
Mechanism of low power laser irradiation on red blood cell deformability
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The effects of laser irradiation on erythrocyte deformability and related mechanism were investigated. Membrane attached hemoglobin (Hbm) is the determinant factor of erythrocyte deformability. After irradiation of 532 nm (30 mW, 20 minutes) or 632.8 nm (30 mW, 60 minutes), the content of Hbm lowered and the deformabilThe effects of laser irradiation on erythrocyte deformability and related mechanism were investigated. Membrane attached hemoglobin (Hbm) is the determinant factor of erythrocyte deformability. After irradiation of 532 nm (30 mW, 20 minutes) or 632.8 nm (30 mW, 60 minutes), the content of Hbm lowered and the deformability of erythrocytes increased, indicating that the decreasing of Hbm is one of the mechanisms of laser action to improve the erythrocyte deformability. The 532-nm laser is more efficient than 632.8 nm laser in the action, which is consistent with the absorption spectrum of Hbm, confirming that the Hbm is the target molecule under laser irradiation..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 182 (2005)
Photostability of thymine and its water complexes
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The photophysical and photochemical properties of electronically excited states of thymine and its water complexes are studied using resonantly enhanced multiphoton ionization spectroscopy. After initial excitation by a nanosecond laser, the excited thymine molecule is trapped in a dark state with a lifetime of tens ofThe photophysical and photochemical properties of electronically excited states of thymine and its water complexes are studied using resonantly enhanced multiphoton ionization spectroscopy. After initial excitation by a nanosecond laser, the excited thymine molecule is trapped in a dark state with a lifetime of tens of nanoseconds. Ionization from this dark state by deep ultraviolet (UV) radiation has a substantially high yield. The lifetime of the dark state is rapidly decreased by adding water molecules. These results indicate that the photostability of our genetic code is not an intrinsic property of the bases themselves. Quenching by solvent water molecules may be the key for the photostability of the DNA bases..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 185 (2005)
Changes of delayed luminescence spectra in rice of different polluted degree by Aspergillus flavus
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Light-induced delayed luminescence (DL) of living organisms contains information on the quality of the living state of these organisms. Employing a LS-55 Luminescence Spectrometer, the changes of DL spectra of rice with Aspergillus flavus treating different time were observed. Rice with Aspergillus flavus treatment forLight-induced delayed luminescence (DL) of living organisms contains information on the quality of the living state of these organisms. Employing a LS-55 Luminescence Spectrometer, the changes of DL spectra of rice with Aspergillus flavus treating different time were observed. Rice with Aspergillus flavus treatment for a shorter time had a stronger intensity of DL. The polluted degree of Aspergillus showed a negative correlation with the intensity of DL. Comparing with the intensity of DL, we found that the concentration of aflatoxin in different polluted degree rice had negative correlation with the intensity of DL. We believe DL technique may be helpful in elaborating a fast, holistic, and non-invasive method for the rapid evaluation the polluted degree of rice by Aspergillus flavus..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 188 (2005)
Basic research on intravascular low intensity laser therapy
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Intravascular low intensity laser therapy (ILILT) was popular in Russia in 1980s and in China in 1990s, respectively. There is photobiomodulation on blood cells and blood in vitro if the radiation intensity is so low that the photodynamic effects of endogenous photosensitizer can not damage membrane or cell compartmentIntravascular low intensity laser therapy (ILILT) was popular in Russia in 1980s and in China in 1990s, respectively. There is photobiomodulation on blood cells and blood in vitro if the radiation intensity is so low that the photodynamic effects of endogenous photosensitizer can not damage membrane or cell compartments and the cells are not in health or normal states. The present in vivo research is of problem as the tip intensity of the fiber-optic used in ILILT might induce the apoptosis or necrosis of the blood cells near to the tip. Obviously, the in vivo research should be further done..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 191 (2005)
Stimulated emission in quasi-periodic photonic crystals
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The stimulated emission in the quasi-periodic photonic crystals is investigated in this paper. It was found that there are some interesting phenomenons in that structure. The lasing is more abundant and stronger compared with that in periodic crystals. More stimulated emission peaks appear when the size and the gain inThe stimulated emission in the quasi-periodic photonic crystals is investigated in this paper. It was found that there are some interesting phenomenons in that structure. The lasing is more abundant and stronger compared with that in periodic crystals. More stimulated emission peaks appear when the size and the gain increase, and some lasing peaks are independent on incident direction, isotropic. These lasing peaks maybe come from the localization of the disorder in the quasi-periodic photonic crystals..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 194 (2005)
Photonic crystal-based optical beam splitter in silicon
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An optical power splitter with one input and three output ports is proposed and demonstrated for near infrared applications in the wavelength range from 2.3 to 2.5 microns. The device operates on the principle of directional coupling by introducing photonic crystal line-defect waveguides. Its functionality and performaAn optical power splitter with one input and three output ports is proposed and demonstrated for near infrared applications in the wavelength range from 2.3 to 2.5 microns. The device operates on the principle of directional coupling by introducing photonic crystal line-defect waveguides. Its functionality and performance have been numerically investigated and simulated by finite-difference time-domain method. Required optical power from each of the output waveguide can be easily controlled by adjusting the coupling length of interaction for photonic crystal line-defect waveguides. The total length of the 1*3 power splitter is 30 microns, which is significantly less than conventional non-photonic crystal power splitter. This is a promising device for future ultracompact and large-scale nanophotonic integrated circuits..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 196 (2005)
An investigation on capabilities of polarization control for immersion lithography through simulation
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The fundamental resolution limit and depth of focus of immersion lithography are described. The image contrasts for TE polarization, TM polarization, and unpolarized condition are explored in detail. There are complications associated with diffraction orders incident on the resist at large incident angles. Image contraThe fundamental resolution limit and depth of focus of immersion lithography are described. The image contrasts for TE polarization, TM polarization, and unpolarized condition are explored in detail. There are complications associated with diffraction orders incident on the resist at large incident angles. Image contrast can be improved or degraded depending on the choice of polarization states. The influence of polarization on processing windows for 65 and 45 nm 1:1 line/space patterns is studied by simulation. It shows the use of vector image lithography simulator to quantify exposure-focus processing window improvements for TE polarization as compared with TM polarization. The results show that the full resolution capabilities of immersion lithography systems can only be realized when the polarization control is used..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 198 (2005)
Femtosecond laser microfabrication of micro-optic elements in glass
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Micro-optic elements have been fabricated in silica and soda-lime glass with femtosecond laser pulses. The dependence of refractive index change on pulse duration, pulse energy and scan passes is investigated and a Fresnel zone plate is induced. A permanent computer-generated hologram encoded by the detour phase methodMicro-optic elements have been fabricated in silica and soda-lime glass with femtosecond laser pulses. The dependence of refractive index change on pulse duration, pulse energy and scan passes is investigated and a Fresnel zone plate is induced. A permanent computer-generated hologram encoded by the detour phase method is directly written by microexplosion. The stored image is reconstructed with a collimated He-Ne laser beam. Three-dimensional microchannels are drilled by water-assisted ablation. At low incident pulse energy, only one transverse microhole is observed. At high incident pulse energy, multiple transverse microholes are simultaneously drilled..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 200 (2005)
Wavelength scaling for multiphoton absorption in semiconductor quantum dots
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We report direct measurements of both magnitude and spectral dispersion of two-photon absorption in organic-capped CdSe quantum dots and three-photon absorption in organic-capped ZnO quantum dots by the use of open-aperture Z-scan technique with femtosecond laser pulses in the wavelength range of 720-950 nm. We find thWe report direct measurements of both magnitude and spectral dispersion of two-photon absorption in organic-capped CdSe quantum dots and three-photon absorption in organic-capped ZnO quantum dots by the use of open-aperture Z-scan technique with femtosecond laser pulses in the wavelength range of 720-950 nm. We find that these nonlinear coefficients are at least an order of magnitude greater than their bulk counterparts. Our experimental data are compared with theories and the rules for wavelength scaling are discussed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 203 (2005)
A new method based on finite-difference time-domain scheme for computing the band structure of 2D photonic crystals
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A finite-difference time-domain (FDTD) scheme in Cartesian coordinate system is developed to analyze the guided-wave properties of a class of two-dimensional (2D) photonic crystals formed by square or triangular arrays of metal posts. With the application of the periodic boundary condition, the computing domain can be A finite-difference time-domain (FDTD) scheme in Cartesian coordinate system is developed to analyze the guided-wave properties of a class of two-dimensional (2D) photonic crystals formed by square or triangular arrays of metal posts. With the application of the periodic boundary condition, the computing domain can be restricted to a unit cell. A modified Yee's grid is introduced to calculate the dispersive characteristic in the case of triangular lattice. As examples, several classic structures are analyzed, numerical results are compared with the results from other methods, and the agreement is found to be very good. This method can also be extended to the three-dimensioned (3D) case..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 205 (2005)
Photo-stability of water-soluble quantum dots in living cells
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Hydrophilic photo luminescent semiconductor quantum dots (QDs) are novel nanometer-size probes, which may have potential using in bio-imaging for biological objects. In this work, the photo-stability of these QDs in two kinds of living cells was studied, compared with conventional biological probes such as fluorescein Hydrophilic photo luminescent semiconductor quantum dots (QDs) are novel nanometer-size probes, which may have potential using in bio-imaging for biological objects. In this work, the photo-stability of these QDs in two kinds of living cells was studied, compared with conventional biological probes such as fluorescein isothiocyanate (FITC) and green fluorescence protein (GFP). It was found that the concentration of QDs in living cells is the dominant factor for its photo-stability in biological environment. When the concentration of the intracellular QDs was high, the QDs show good photo-stability that is much better than the organic fluorescent probes. However when its concentration was low, the QDs also can be photo-bleached quickly. Thus the reaching of the certain concentration level is the critical condition for QDs in the application of bio-imaging..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 208 (2005)
Optimum design of anti-resonant reflecting photonic crystal vertical-cavity surface-emitting lasers
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Anti-resonant reflecting photonic crystal structure in vertical-cavity surface-emitting lasers (VCSELs) to achieve photon confinement in lateral direction is introduced. This kind of design is proposed to support large aperture single-mode emission. A proper method to fabricate the proposed structure has also been discAnti-resonant reflecting photonic crystal structure in vertical-cavity surface-emitting lasers (VCSELs) to achieve photon confinement in lateral direction is introduced. This kind of design is proposed to support large aperture single-mode emission. A proper method to fabricate the proposed structure has also been discussed. Firstly a spacer layer will be fabricated between the active layer and pDBR layer. A hexagonal array of high-index cylinders will be designed by etching and re-growth on the spaced layer. The transverse modal property of the proposed structure has been investigated. An optimum design for the minimum radiation loss by considering of the cylinder diameter has been discussed in this paper..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 210 (2005)
Absorptive and refractive nonlinearity of carbon nanotubes grown on Si substrate
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The third-order susceptibility of multiwalled carbon nanotubes (MWCNTs) grown on Si substrate were measured using reflective Z-scan (RZ-scan) technique with femto-second laser pulses at 790 nm. The nonlinear absorption coefficient 'beta' and nonlinear refraction index 'gamma' were measured to be about 9The third-order susceptibility of multiwalled carbon nanotubes (MWCNTs) grown on Si substrate were measured using reflective Z-scan (RZ-scan) technique with femto-second laser pulses at 790 nm. The nonlinear absorption coefficient 'beta' and nonlinear refraction index 'gamma' were measured to be about 9*10^(2) cm/GW and 9.6*10^(-3) cm2/GW, respectively. This is about one order of magnitude larger than the measurement of MWCNTs on transparent quartz substrate. The enhanced optical nonlinearities are contributed by the enhanced local field and the photoinduced off-resonant absorption of the 'pi'-plamon of MWCNTs on Si..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 213 (2005)
Uptake of water-soluble CdTe quantum dots in living cells of euglena gracilis
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Water-soluble CdTe quantum dots (QD600) were synthesized by hydrothermal route. The uptake of QD600 in living cells of euglena gracilis was studied. The luminescence spectra show that the QD600 were bound in cells after incubation. The fluorescence images, measured by confocal laser scanning microscope, demonstrate thaWater-soluble CdTe quantum dots (QD600) were synthesized by hydrothermal route. The uptake of QD600 in living cells of euglena gracilis was studied. The luminescence spectra show that the QD600 were bound in cells after incubation. The fluorescence images, measured by confocal laser scanning microscope, demonstrate that the QD600 can penetrate into the cells. The amount of cell-bound QD600 increased with incubation time of QD600 at 25 Celsius deg., but no detectable QD600 were found in the cells when the incubation temperature was 4 Celsius deg., it was suggested that the QD600 were actively taken into the cells by endocytotic pathway. These results indicate that the water-soluble CdTe quantum dots have the potential in the application of bio-labeling..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 216 (2005)
Designing resonant cavity made up of photonic crystal
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Defect is built as that in the semiconductor when some metal posts are withdrawn regularly from the two-dimensional (2D) photonic crystal (PC) formed by triangular arrays of metal posts. Such defect can be used to design cavity. The relation among the lattice, the radius of post, the mode and frequency of this kind of Defect is built as that in the semiconductor when some metal posts are withdrawn regularly from the two-dimensional (2D) photonic crystal (PC) formed by triangular arrays of metal posts. Such defect can be used to design cavity. The relation among the lattice, the radius of post, the mode and frequency of this kind of cavity is researched in this paper. The design of this kind of cavity is introduced..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 218 (2005)
Study on the temperature measure of the gene transfection apparatus
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Electroporation is a physical process that transiently permeabilizes prokaryotic and eukaryotic cell membranes with an electrical pulse, permitting cell uptake of a variety of biological molecules. Because of the advantages of high efficiency, low toxicity popularity, and controllability, it has been applied in the fieElectroporation is a physical process that transiently permeabilizes prokaryotic and eukaryotic cell membranes with an electrical pulse, permitting cell uptake of a variety of biological molecules. Because of the advantages of high efficiency, low toxicity popularity, and controllability, it has been applied in the fields such as cell engineering, genetic engineering, and so on. The principles and characteristics of gene transfection apparatus which is made by us will be illustrated in this paper. The temperature influence is considered and the optical fiber sensor in the apparatus is proposed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 221 (2005)
Fabrication of complex nanostructures based on laser manipulation of atoms
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Atom lithography suffers from serious practical limitations, which have limited the application of this technique in practice. Double deposition method, manipulation of atoms with a linear polarization gradient laser field and moving substrate during deposition process to fabricate nanostructure with a period less thanAtom lithography suffers from serious practical limitations, which have limited the application of this technique in practice. Double deposition method, manipulation of atoms with a linear polarization gradient laser field and moving substrate during deposition process to fabricate nanostructure with a period less than half an optical wavelength, was discussed. The atomic density distribution transversal to the beam direction closely mimics the light intensity pattern, and the structures are equally complex as the inducing light intensity. The variety of patterns and the role of the different parameters were discussed. The optical focusing of group III atoms provides a new approach for controlling the spatial composition of atoms during the growth of III-V heterostructures..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 223 (2005)
Finite element analysis of the light distribution of the near infrared probe to assist brain neurosurgical guidance
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Finite element analysis is used to study the near infrared light distribution in brain tissue. The diameter of the light beam varies from 100 microns to 1 mm. The researching results indicate that the near infrared light distribution in brain tissue gets wider with rising of the beam diameter, and the distribution fielFinite element analysis is used to study the near infrared light distribution in brain tissue. The diameter of the light beam varies from 100 microns to 1 mm. The researching results indicate that the near infrared light distribution in brain tissue gets wider with rising of the beam diameter, and the distribution fields are 0.05-0.2 mm below the probe, respectively. At last, the results of finite element analysis are verified by Monte-Carlo simulation, which prove the feasibility of using near infrared light in brain surgical guidance..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 226 (2005)
Monte-Carlo study for look ahead distance of near-infrared probe for neurosurgical microwound manipulation
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Monte-Carlo simulation was used to study photon distribution in brain tissue, look ahead distance (LAD) empirical formula and theoretical model of near-infrared (NIR) neurosurgical manipulation microwound probe were obtained from the light distribution simulation. LAD empirical formula was verified by phantom and intraMonte-Carlo simulation was used to study photon distribution in brain tissue, look ahead distance (LAD) empirical formula and theoretical model of near-infrared (NIR) neurosurgical manipulation microwound probe were obtained from the light distribution simulation. LAD empirical formula was verified by phantom and intralipid experiments. The experiment results are valuable for designing neurosurgical microwound probe..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 229 (2005)
Photon theory of bio-electromagnetic athermal effect
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The formula <n>d=d/2, which describes bio-electromagnetic athermal effect, is deduced employing quantum theory. This law shows that the bio-electromagnetic athermal effect has no relation to the irradiation power, but to the structure of the living tissues. The phenomena about multi-photon absorption and bio-eThe formula <n>d=d/2, which describes bio-electromagnetic athermal effect, is deduced employing quantum theory. This law shows that the bio-electromagnetic athermal effect has no relation to the irradiation power, but to the structure of the living tissues. The phenomena about multi-photon absorption and bio-electromagnetic athermal effect may occur in cell membrane. Finally, the assumption how to test this theory is put forward..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 232 (2005)
Effects of alcohol on fluorescence spectra of erythrocyte solution
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Based on the experimental researches on the fluorescence spectra of 1% erythrocyte solution with various concentration of alcohol excited by violet light-emitting diode LED light at 407 nm, the mechanism of alcohol on the fluorescence spectra of erythrocyte solution is investigated theoretically. The experiment resultsBased on the experimental researches on the fluorescence spectra of 1% erythrocyte solution with various concentration of alcohol excited by violet light-emitting diode LED light at 407 nm, the mechanism of alcohol on the fluorescence spectra of erythrocyte solution is investigated theoretically. The experiment results indicate that induced by the LED light at 407 nm, erythrocyte solution with the concentration of 1% can emitting striking spectra with two fluorescence regions. One is the short-wave fluorescence region from 430 to 525 nm, and the other is the long-wave fluorescence region from 580 to 750 nm. When the concentration of alcohol in erythrocyte solution increasing, the fluorescence intensity of short-wave area decrease while the fluorescence intensity of long-wave area increases. Combining the blood absorb spectra to the experiment results, it is shown that the formation of the short-wave fluorescence area is because the solution transmits the fluorescence spectra and the self-absorption of erythrocyte. The long-wave fluorescence region comes from porphyrin such as protoporphyrin, zinc porphyrin etc.. And there is resonance energy transmission between the short-wave fluorophores and the long-wave ones. According to the experiment results and the physical theory in erythrocyte fluorescence, it is found that alcohol make higher self-absorption ratio of the erythrocyte which improves the resonance energy transmission between fluorophores in the two wave bands. The result will offer experimental and theoretical reference for examining the alcohol content in blood..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 235 (2005)
Image reconstruction algorithm of near infrared optical tomography
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The principle of the algorithm for stability near infrared (NIR) optical Tomography (CT) is introduced. The forward problem of optical CT is how to solve the Boltzmann transmitting equation based on finite rlement method (FEM). The influence of high reduced scattering coefficient and high absorption coefficient distribThe principle of the algorithm for stability near infrared (NIR) optical Tomography (CT) is introduced. The forward problem of optical CT is how to solve the Boltzmann transmitting equation based on finite rlement method (FEM). The influence of high reduced scattering coefficient and high absorption coefficient distribution of simulation background was discussed. The inverse problem is to reconstruct the map of the background tissue from the boundary data, and the image reconstruction algorithm is the key problem for optical CT. Generic algorithm (GA) and FEM simulation was used to solve the inverse problem..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 237 (2005)
Identification of maize seeds by terahertz scanning imaging
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Varietal purity is the most important quality parameter of maize seeds, which has direct and prominent influence on the output and quality of maize. For the first time, to our knowledge, we present a new kind of terahertz (THz) scanning imaging technology for identification of maize seeds. Terahertz images of DNA samplVarietal purity is the most important quality parameter of maize seeds, which has direct and prominent influence on the output and quality of maize. For the first time, to our knowledge, we present a new kind of terahertz (THz) scanning imaging technology for identification of maize seeds. Terahertz images of DNA samples are obtained by point-by-point scanning imaging technology. Inspection and identification of specific kinds of seeds are realized successfully by using the method of component pattern analysis. In this method, what we need are only data of image and absorption spectral information of samples; no specific features of samples are required. This technology provides a new approach for the detection and identification in biology and it can also be extended to poison inspection..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 239 (2005)
Crystal structure and PL spectrum of ZnO films prepared by DC magnetic control sputtering
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ZnO is an n-type semiconductor having a hexagonal wurtzite structure. By X-ray diffraction (XRD) and scanning electron microscope (SEM), the influences of substrate temperature, the ratio of Ar to O2 and thermal temperature on ZnO crystal quality were studied. The results show that ZnO films deaposited at substrate temZnO is an n-type semiconductor having a hexagonal wurtzite structure. By X-ray diffraction (XRD) and scanning electron microscope (SEM), the influences of substrate temperature, the ratio of Ar to O2 and thermal temperature on ZnO crystal quality were studied. The results show that ZnO films deaposited at substrate temperature of 240 Celsius degrees and Ar:O2=1:3 have the best crystallization. UV photoluminescence is observed when ZnO films are excited by He-Cd laser at room temperature. Stress at boundary causes an intrinsic UV emission peak shift to the lower energy. Oxygen vacancy or zinc interstitial causes deep-level emission. With higher substrate temperature, the crystallization is improved and the stress and deep-level green emission are reduced..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 242 (2005)
Influence of the strain on the energy levels of semiconductor quantum dots
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We systematically investigate a strain of self-assembled InAs/GaAs quantum dots (QDs) for the case of growth on a (001) substrate. The dependence of the biaxial and hydrostatic components of the strain on the quantum dot aspect ratio is studied using a finite element method. The dependence of the carrier's confininWe systematically investigate a strain of self-assembled InAs/GaAs quantum dots (QDs) for the case of growth on a (001) substrate. The dependence of the biaxial and hydrostatic components of the strain on the quantum dot aspect ratio is studied using a finite element method. The dependence of the carrier's confining potentials is then calculated in the framework of eight-band kp theory. The shifts of the energy level in three shapes of QDs are investigated. By comparing the results, the influence of the strain on the QDs are given..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 244 (2005)
Research of strain state and dislocation density in the multiple AlGaN epitaxial layers with high Al content
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In this paper, the p-i-n multiple-layer Al~~(x)Ga~~(1-x)N sample with high Al (x>0.45) content was measured by the triple-axis X-ray diffraction measurement. The strain state and screw dislocation density of each layer in Al~~(x)Ga~~(1-x)N epitaxial layers were determined by RSM (reciprocal space map) method. TheIn this paper, the p-i-n multiple-layer Al_(x)Ga_(1-x)N sample with high Al (x>0.45) content was measured by the triple-axis X-ray diffraction measurement. The strain state and screw dislocation density of each layer in Al_(x)Ga_(1-x)N epitaxial layers were determined by RSM (reciprocal space map) method. Then, the PV function was used to fit the rock curves separated from the RSM. At last, the strain and the screw dislocation density of each layer were accurately calculated by fitting these rock curves..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 246 (2005)
Optical nonlinearities and optical limiting properties of PbS semiconductor nano-belts
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The third-order nonlinearities of PbS nano-belts have been investigated using the Z-scan technique with nanosecond laser pulses at 532 nm. The effect of the PbS semiconductor nano-belt size on the third-order optical nonlinearities and optical limiting properties was studied. We found that the nonlinear absorption and The third-order nonlinearities of PbS nano-belts have been investigated using the Z-scan technique with nanosecond laser pulses at 532 nm. The effect of the PbS semiconductor nano-belt size on the third-order optical nonlinearities and optical limiting properties was studied. We found that the nonlinear absorption and nonlinear refraction have not strict dependence on the nano-belt size under our investigated condition, but their optical limiting behavior is different. The optical limiting mechanism of materials is discussed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 248 (2005)
Study of optical gain from square-nested PCFs with impurities
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Using numerical simulation method based on finite-difference time-domain (FDTD), we study the characteristics of the multiple-core photonic crystal fibers (PCFs) in which square-nested compound lattices (SNCLs) with several defect regions are introduced. We find that each line defect in the PCFs can serve as a channel Using numerical simulation method based on finite-difference time-domain (FDTD), we study the characteristics of the multiple-core photonic crystal fibers (PCFs) in which square-nested compound lattices (SNCLs) with several defect regions are introduced. We find that each line defect in the PCFs can serve as a channel in wavelength division multiplexing (WDM) communication systems. The crosstalk can be suppressed because there is a band gap among each channel in the PCFs. And PCF amplifiers are expected to be used in the super-dense WDM systems..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 251 (2005)
Optical properties of align carbon nanotubes film
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The optical properties of carbon nanotubes are studied. Align carbon nanotubes films were synthesized by chemical vapour deposition method in our lab. The diameter of carbon nanotube is about 20-30 nm. The amorphous carbon impurities in align carbon nanotubes film were removed by a series of deal with processes. CarbonThe optical properties of carbon nanotubes are studied. Align carbon nanotubes films were synthesized by chemical vapour deposition method in our lab. The diameter of carbon nanotube is about 20-30 nm. The amorphous carbon impurities in align carbon nanotubes film were removed by a series of deal with processes. Carbon nanotubes were examined up by using scanning electron microscope, transmission electron microscope and Raman spectrum.The reflected spectrum, transmission spectrum and absorption were measured. Results show that carbon nanotubes have strong absorption from visible region to mid-infrared (IR) region. Photoluminescence spectra of carbon naotubes film were studied at 488, 632.8, and 1060 nm excited laser wavelength. Results show sthat there are nonlinear processes in luminescence of carbon nanotubes under ultrafast laser excitation (1064 nm, 60 ps) conditions. A broad photoluminescence peak was location at 1.6 eV (about 768 nm), this phenomenon was considered to relate to van Hove singularities, and was a three-photon-absorption process..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 253 (2005)
Imaging and tracking single fluorescent nanobeads in solution
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In single-particle tracking (SPT), fluorescence video microscopy is used to record the motion images of single particle or single molecule. Here, by using a total-internal-reflection microscope equipped with an argon ion laser and a charge-coupled device (CCD) camera with high-speed and high-sensitivity, video images oIn single-particle tracking (SPT), fluorescence video microscopy is used to record the motion images of single particle or single molecule. Here, by using a total-internal-reflection microscope equipped with an argon ion laser and a charge-coupled device (CCD) camera with high-speed and high-sensitivity, video images of single nanobeads in solutions were obtained. From the trajectories, the diffusion coefficient of individual nanobead was determined by the mean square displacements as a function of time. The sizes of nanobeads were calculated by Stokes-Einstein equation, and the results were compared with the actual values..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 256 (2005)
Preparation and spectral characteristics of ZnS:Cu modification with nanoparticles ZnO
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The nanoparticles ZnO had been prepared on the surface of ZnS:Cu by homogeneous precipitate method. The urea was used as precipitator in the process of hydrolysis reaction. X-ray diffraction (XRD) and infrared (IR) spectra indicated that ZnO was formed. We also observed fluorescence spectra, there was some difference bThe nanoparticles ZnO had been prepared on the surface of ZnS:Cu by homogeneous precipitate method. The urea was used as precipitator in the process of hydrolysis reaction. X-ray diffraction (XRD) and infrared (IR) spectra indicated that ZnO was formed. We also observed fluorescence spectra, there was some difference between the raw material and coated materials in fluorescence intensity..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 259 (2005)
Time-resolved photoluminescent spectra of CdSe quantum dots with surface treatment
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The surface morphology is one of the important factors to determine the optical properties of colloidal quantum dots. Colloidal CdSe dots were synthesized by the injection of precursor molecules in a hot surfactant, and a series of samples were obtained by partially replacing the ligands on the surface of these dots wiThe surface morphology is one of the important factors to determine the optical properties of colloidal quantum dots. Colloidal CdSe dots were synthesized by the injection of precursor molecules in a hot surfactant, and a series of samples were obtained by partially replacing the ligands on the surface of these dots with 2-mercaptoethanol. 2-mercaptoethanol results in the decrease of the photoluminescent quantum yield, and the time-resolved photoluminescent (PL) spectra are significantly modified. The effect of the surface morphology is discussed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 261 (2005)
Characterization of the dynamics of photonic crystal molecules with Kerr nonlinearity by numerical pump-probe simulations
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We investigate the dynamics of photonic crystal (PC) molecules with Kerr nonlinearity by numerical simulations in a pump-probe scheme based on the finite-difference time-domain technique. The constitutional PC atoms of the nonlinear PC molecules are intentionally chosen to be multimode so that the pump and probe waves We investigate the dynamics of photonic crystal (PC) molecules with Kerr nonlinearity by numerical simulations in a pump-probe scheme based on the finite-difference time-domain technique. The constitutional PC atoms of the nonlinear PC molecules are intentionally chosen to be multimode so that the pump and probe waves can be set at different frequencies, ensuring the clear identification of the dynamics of nonlinear PC molecules. Being more complicated than the dynamics of nonlinear PC atoms, we reveal that the coupling between the PC atoms plays an important role in determining the dynamical responses of nonlinear PC molecules to the excitation of ultrashort pulses. It is reflected in fact that PC molecules with different spectral shapes exhibit different dynamical response behaviors..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 263 (2005)
Effect of multi-point defects on the bandgap and defect mode of two-dimensional photonic crystal
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Bandgap and defect mode are important properties of two-dimensional (2D) photonic crystal, which determine the application of photonic crystal. At present, researchers have done a large amount of studying on point defect and line defect photonic crystal. In this paper, we introduce multi-point defects into 2D photonic Bandgap and defect mode are important properties of two-dimensional (2D) photonic crystal, which determine the application of photonic crystal. At present, researchers have done a large amount of studying on point defect and line defect photonic crystal. In this paper, we introduce multi-point defects into 2D photonic crystal by removing medium rods (InGaAsP), and then simulate their bandgap and mode field using plane wave method (PWM). The simulation results are useful to design the multi-wavelength photonic crystal laser..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 266 (2005)
A scheme for quantum state transfer between distant atoms
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A scheme is proposed to implement quantum state transfer between two distant atoms through sending the atoms across two distant cavities connected via an optical fiber. The field state, which preserves the information of the first atom, is transmitted from one cavity to the other along the fiber. After the field interaA scheme is proposed to implement quantum state transfer between two distant atoms through sending the atoms across two distant cavities connected via an optical fiber. The field state, which preserves the information of the first atom, is transmitted from one cavity to the other along the fiber. After the field interacts with the second atom for a defined time, the state transfer can be accomplished with unit efficiency. The realization of this scheme is within current experiment technology..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 269 (2005)
Probe spectrum in photonic crystal
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The probe absorption spectrum of a four-level atom embedded in a double-band photonic crystal is discussed in this paper. The double V-type transitions from the two upper levels to the two lower levels interact with the free vacuum modes and the photonic band gap (PBG) modes synchronously. We investigate the quantum inThe probe absorption spectrum of a four-level atom embedded in a double-band photonic crystal is discussed in this paper. The double V-type transitions from the two upper levels to the two lower levels interact with the free vacuum modes and the photonic band gap (PBG) modes synchronously. We investigate the quantum interferences in the probe absorption spectrum. And the new features of transparency are also predicted..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 272 (2005)
1*N dynamic optical coupler based on Dammann gratings
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We present two novel 1*N dynamic optical couplers that are based on Dammann gratings to achieve dynamic optical coupled technology. One is presented by employing a specially designed Dammann grating that consists of the Dammann-grating area and the blank area. The other is developed by using two complementary even-numbWe present two novel 1*N dynamic optical couplers that are based on Dammann gratings to achieve dynamic optical coupled technology. One is presented by employing a specially designed Dammann grating that consists of the Dammann-grating area and the blank area. The other is developed by using two complementary even-numbered Dammann gratings. The couplers can achieve the function conversion between a beam splitter and a combiner according to the modulation of the gratings. We have experimentally demonstrated 1*8 dynamic optical couplers at the wavelength of 1550 nm. The experimental results and the analyses are reported in detail..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 275 (2005)
Studies on all-fiber Raman fiber lasers with domestic Bragg gratings
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Research of the first-order Raman fiber laser pumped by a continuous wave (CW) fiber laser is presented using domestic Bragg gratings with corning SMF-28TM silica fiber as the gain material. Formation process of Raman laser is studied and output characteristics are measured. Laser output is centered at 1116 nm with 3-dResearch of the first-order Raman fiber laser pumped by a continuous wave (CW) fiber laser is presented using domestic Bragg gratings with corning SMF-28TM silica fiber as the gain material. Formation process of Raman laser is studied and output characteristics are measured. Laser output is centered at 1116 nm with 3-dB bandwidth of 0.18 nm. Pump threshold is estimated, which is in good agreement with the experimental value by revising the equation in some references. Techniques for decreasing threshold power and increasing output power are also analyzed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 277 (2005)
Effective polarization splitters based on dual-core photonic crystal fibers with elliptical holes
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We investigate the coupling characteristics in dual-core photonic crystal fibers (PCFs) with elliptical air holes and their applications in the construction of polarization splitters by use of a full-vector beam propagation method. The numerical simulation results indicate the possibility of realizing a polarization spWe investigate the coupling characteristics in dual-core photonic crystal fibers (PCFs) with elliptical air holes and their applications in the construction of polarization splitters by use of a full-vector beam propagation method. The numerical simulation results indicate the possibility of realizing a polarization splitter with an extinction ratio better than -20 dB at 1.55 microns and a total length of only 1.651 mm. It is also revealed that the total length of the polarization splitters can be further reduced by properly doping the core regions of the PCFs..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 280 (2005)
Properties of splitting light with metal nanoparticles arrays
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A model of a structure consisting of nonperiodic closely spaced metal nanoparticles array, in which electromagnetic energy can be transported and splitted below the diffraction limit, is founded. Based on finite difference time domain (FDTD) algorithm, we analyze the power transmission properties of nonperiodic silver A model of a structure consisting of nonperiodic closely spaced metal nanoparticles array, in which electromagnetic energy can be transported and splitted below the diffraction limit, is founded. Based on finite difference time domain (FDTD) algorithm, we analyze the power transmission properties of nonperiodic silver nanoparticles arrays in a dielectric waveguide. The numerical results indicate the structure can split light along the array at the nanometer level with no radiative losses at the discontinuity..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 284 (2005)
A scheme for assisted cloning of a two-particle entangled state via GHZ class states
We propose a protocol where one can realize quantum cloning of an unknown two-particle entangled state and its orthogonal complement state with assistance offered by a state preparer. The first stage of the protocol requires usual teleportation using a (or two) four-particle entangled state(s) as quantum channel(s). InWe propose a protocol where one can realize quantum cloning of an unknown two-particle entangled state and its orthogonal complement state with assistance offered by a state preparer. The first stage of the protocol requires usual teleportation using a (or two) four-particle entangled state(s) as quantum channel(s). In the second stage of the protocol, with the assistance (through a two-particle projective measurement) of the preparer, the perfect copies and complement copies of an unknown state can be produced..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 286 (2005)
Nondestructive determination for the thickness of spin-coated polymer films by transparent coefficient
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Polymer films thickness is one of the critical factors for the operation performance of the integrated optical devices (IODs) based on polymer planar waveguides and it is difficult to real-time determine it during corresponding fabrication process. A variety of approaches, which have been presented before, are either oPolymer films thickness is one of the critical factors for the operation performance of the integrated optical devices (IODs) based on polymer planar waveguides and it is difficult to real-time determine it during corresponding fabrication process. A variety of approaches, which have been presented before, are either of less precision or more contamination of the film surfaces. In this paper a practical method, in which the absorbance of the polymer film using Lanbert law to determine the thickness of spin-coated polymer films, was presented. Compared with other methods, it can get an acceptable accuracy without using specialized and expensive instruments, and the surface of the film with not be contaminated during the measurement process. The experimental results compared with other methods were listed and depicted in confirming our method's availability. The factors that may have influence on the employment of our method were analyzed and discussed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 290 (2005)
Color-tunable triple-layer electroluminescent devices based on organic salt
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A triple-layer light-emitting diode based on an organic salt ASPT (trans-4-[p-[N-methyl-N-(hydroxyethyl)amino]styryl]-N-methylpyridinium tetraphenylborate), in which TPD and Alq3 were employed as hole and electron transporting materials respectively, exhibits variable electroluminescence (EL) spectra under different apA triple-layer light-emitting diode based on an organic salt ASPT (trans-4-[p-[N-methyl-N-(hydroxyethyl)amino]styryl]-N-methylpyridinium tetraphenylborate), in which TPD and Alq3 were employed as hole and electron transporting materials respectively, exhibits variable electroluminescence (EL) spectra under different applied voltage. At lower voltage, the EL spectrum peaks at 560 nm, which emanates from the TPD/ASPT interface; when the voltage is further increased, the peak at 610 nm, which is originated from ASPT, increases; at higher applied voltage, the device yields green light with a peak at 530 nm and a shoulder at 610 nm. The stronger emission peaking at 530 nm stems from the Alq3. It reveals the hole-electron recombination zone depends on the applied voltage, so the color-variable EL can be observed by adjusting the applied voltage..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 293 (2005)
Two-color recording performance in Mn-doped near-stoichiometric LiNbO3 crystals
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Two-color holographic recording was performed in near-stoichiometric LiNbO3 crystals doped with 50-ppm Mn, where the crystals were thermally annealed in different oxidation/reduction atmospheres. Two-color recording properties including sensitivity, dynamic range, activity energy, and dark decay time were measured and Two-color holographic recording was performed in near-stoichiometric LiNbO3 crystals doped with 50-ppm Mn, where the crystals were thermally annealed in different oxidation/reduction atmospheres. Two-color recording properties including sensitivity, dynamic range, activity energy, and dark decay time were measured and compared, and the results were explained reasonably by measuring some characteristic material parameters..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 295 (2005)
Photoelectron decay characteristic of cubic AgCl emulsion sensitized by green-sensitizing dye
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The free photoelectron signals of spectral sensitized AgCl emulsion with different sensitization concentrations are obtained from microwave absorption dielectric spectrum experiment. It is found that when sensitization concentration is small (0.04 mg dye per 40 g AgCl emulsion) or great (4 mg dye per 40 g AgCl emulsionThe free photoelectron signals of spectral sensitized AgCl emulsion with different sensitization concentrations are obtained from microwave absorption dielectric spectrum experiment. It is found that when sensitization concentration is small (0.04 mg dye per 40 g AgCl emulsion) or great (4 mg dye per 40 g AgCl emulsion), the decay of free photoelectron of sensitized emulsion is slower or faster than that of pure emulsions; when sensitization concentration is between the above values (0.4 mg dye per 40 g AgCl emulsion), the decay of free photoelectron is the same for sensitized and pure emulsion. The results indicate that the adsorbed green-sensitizing dye on the surface of cubic AgCl microcrystals takes on different actions with different sensitization concentrations..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 298 (2005)
Preparation, characterization, and electro-optic properties of nonlinear optical nanohybrid
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The polyimide-silica nonlinear optical (NLO) hybrid materials with covalent links between the inorganic and the organic networks were synthesized by the sol-gel method. The prepared hybrids were characterized by IR, TGA, XRD, SEM, TEM and can be easily spin-coated, ensuring long-term alignment stability at elevated temThe polyimide-silica nonlinear optical (NLO) hybrid materials with covalent links between the inorganic and the organic networks were synthesized by the sol-gel method. The prepared hybrids were characterized by IR, TGA, XRD, SEM, TEM and can be easily spin-coated, ensuring long-term alignment stability at elevated temperatures. These devices exhibit large electro-optic coefficients at 832 nm. The experimental results suggest that the hybrid thin films have potential applications as passive films for optical devices..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 301 (2005)
Two-photon spectra of organic salt trans-4- [p-(N-hydroxyethyl-N-methylamino)styryl]-N- methylpyridinium iodide in two solvents
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Two-photon absorption (TPA) cross sections of an organic dye, trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methylpyridinium iodide (abbreviated as ASPI), from 810 to 1100 nm have been measured in two solvents (benzyl alcohol, dimethyl formamide (DMF)) with different polarities. The peak values and positions of ASTwo-photon absorption (TPA) cross sections of an organic dye, trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methylpyridinium iodide (abbreviated as ASPI), from 810 to 1100 nm have been measured in two solvents (benzyl alcohol, dimethyl formamide (DMF)) with different polarities. The peak values and positions of ASPI TPA spectra were found to be strongly influenced by the solvents. The maximum molecular TPA cross sections are 26.42*10^(-48) cm4 s/photon at 930 nm (in DMF solution) and 46.81*10^(-48) cm4 s/photon at 960 nm (in benzyl alcohol solution)..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 303 (2005)
Synthesis and NLO properties of chromophores with calix[4] arene and ring-locked trienes
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The new chromophore molecules with nonlinear optical (NLO) properties were prepared by Knoevenagel condensation from diformyl calix[4]arene and isophorone derivatives in the presence of piperidine and acetic acid, respectively. In these chromophore calix[4]arenes, the ring-locked trienes were employed as the conjugatioThe new chromophore molecules with nonlinear optical (NLO) properties were prepared by Knoevenagel condensation from diformyl calix[4]arene and isophorone derivatives in the presence of piperidine and acetic acid, respectively. In these chromophore calix[4]arenes, the ring-locked trienes were employed as the conjugation bridge and electron acceptor in D-'pi'-A units. Nuclear magnetic resonance (NMR) spectra indicate that the non-conjugated D-'pi'-A units can be oriented at nearly the same direction. Hyper-Rayleigh Scatting (HRS) measurements and ultraviolet (UV) spectra indicate that they have higher first hyperpolarizability 'beta' values than the corresponding reference compounds and are not accompanied with a large shift (>25 nm) of the absorption band to longer wavelengths..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 306 (2005)
Numerical simulation of laser-generated Lamb wave by finite element method in thin transversely isotropic laminate composite
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Laser ultrasound is a technique based on lasers to generate and detect ultrasound remotely. The thermal expansion arising from the optical absorption of a short laser pulse generates ultrasonic wave. By using finite element method, this study presents a source model for laser ultrasonic generation in thin transversely Laser ultrasound is a technique based on lasers to generate and detect ultrasound remotely. The thermal expansion arising from the optical absorption of a short laser pulse generates ultrasonic wave. By using finite element method, this study presents a source model for laser ultrasonic generation in thin transversely isotropic laminate composite in the thermoelastic regime. According to the thermoelastic theory, the transient temperature is equivalent to a body source to generate ultrasonic waves. The numerical results indicate that the symmetric and antisymmetric Lamb wave is excited in thin transversely isotropic laminate composite plate, the evolution of the dispersive waveform is a function of the source-receiver distance, the plate thickness, and the parameters of the fiber-reinforced composite. These results are very useful for evaluation materials parameters of the composite plate..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 308 (2005)
Photoelectron time-resolved spectra of silver halide microcrystal adsorbed with spectral sensitizing dye
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Microwave absorption and dielectric spectral detection technology with high time resolution (1 ns) is used for contactless measurement of electron property in solid materials. In this paper, the free photoelectron time-resolved spectra of cubic AgCl emulsion sensitized by green-sensitizing dye are measured by dielectriMicrowave absorption and dielectric spectral detection technology with high time resolution (1 ns) is used for contactless measurement of electron property in solid materials. In this paper, the free photoelectron time-resolved spectra of cubic AgCl emulsion sensitized by green-sensitizing dye are measured by dielectric spectral equipment. The samples are exposed to 35-ps short pulse laser at 355 and 532 nm, respectively. The results show that for the same sensitized sample, the free photoelectron lifetime are 43.1 and 5.8 ns, respectively. And for the same wavelength, the lifetime of sensitized emulsion is shorter than that of pure emulsion. It is thus proved that the adsorption of dyes to silver halide microcrystals increases the Ag_(i)+ concentration..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 311 (2005)
Advantages of photon scanning tunneling microscope combined with atomic force microscope
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A new nano-meter scale resolution optical imaging mode and functional prototype of photon scanning tunneling microscope (PSTM) combined with atomic force microscope (AFM) named as AF/PSTM are introduced, and the advantages of AF/PSTM are discussed. Two separated optical images (refractive index image and transmissivityA new nano-meter scale resolution optical imaging mode and functional prototype of photon scanning tunneling microscope (PSTM) combined with atomic force microscope (AFM) named as AF/PSTM are introduced, and the advantages of AF/PSTM are discussed. Two separated optical images (refractive index image and transmissivity image) and two AFM images (topography image and phase image) of sample can be obtained during AF/PSTM's once scanning. AF/PSTM is applicable to all transmission samples in many fields, such as nano-biology, medicine, nano-optics, nano-industry, nano-science and technology, high-education and so on..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 313 (2005)
Comparison of AF/RSNOM with other RSNOM
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AF/RSNOM is a new kind of scanning probe microscope developed in our lab, which is a combination of atomic force microscope and reflection scanning near field optical microscopy (AF/RSNOM) working in equi-amplitude tapping mode. This paper introduces the principle of AF/RSNOM and its advantages compared with other reflAF/RSNOM is a new kind of scanning probe microscope developed in our lab, which is a combination of atomic force microscope and reflection scanning near field optical microscopy (AF/RSNOM) working in equi-amplitude tapping mode. This paper introduces the principle of AF/RSNOM and its advantages compared with other reflection mode scanning optical microscopes (RSNOM). Compared with the former RSNOM, this tapping mode AF/RSNOM has convenient operation and fewer background signals..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 316 (2005)
Temporal characteristic simulation for stimulated emission depletion microscopy
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The imaging technology of stimulated emission depletion (STED) utilizes the nonlinearity relationship between the fluorescence saturation and the excited state stimulated depletion. It implements three-dimensional (3D) imaging and breaks the diffraction barrier of far-field light microscopy by restricting fluorescent mThe imaging technology of stimulated emission depletion (STED) utilizes the nonlinearity relationship between the fluorescence saturation and the excited state stimulated depletion. It implements three-dimensional (3D) imaging and breaks the diffraction barrier of far-field light microscopy by restricting fluorescent molecules at a sub-diffraction spot. In order to improve the resolution which attained by this technology, the computer simulation on temporal behavior of population probabilities of the sample was made in this paper, and the optimized parameters such as intensity, duration and delay time of the STED pulse were given..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 318 (2005)
Measurement system of gas density based on spectrum absorption
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A novel measurement system for the gas density based on spectrum absorption is studied in details. Based on the theory of Beer-Lambert, the technology of nonlinear laser diode (LD) spectrum is used to perform the polluting gases monitoring on line. The peak wavelengths of LD are changed with the applied voltage and temA novel measurement system for the gas density based on spectrum absorption is studied in details. Based on the theory of Beer-Lambert, the technology of nonlinear laser diode (LD) spectrum is used to perform the polluting gases monitoring on line. The peak wavelengths of LD are changed with the applied voltage and temperature, so the technology of wavelength modulating or frequency modulating can be used at perform the measurement in wide scope. In this paper, the low density of the polluting gases, is detected by the method of harmonic detection in order to increase the detection sensitivity..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 322 (2005)
One new method for OCT image denoising based on wavelet transform
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Optical coherence tomography (OCT) suffers from random noises which degrade contrast of image, these noises can not effectively be wiped off by filtering technique. Characteristics of random noises were discussed and analyzed, noise influences were identified on image. The method of wavelet transform is presented for iOptical coherence tomography (OCT) suffers from random noises which degrade contrast of image, these noises can not effectively be wiped off by filtering technique. Characteristics of random noises were discussed and analyzed, noise influences were identified on image. The method of wavelet transform is presented for image denoising. The result shows that the method can reduce image noises..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 324 (2005)
Study of spatially resolved diffuse reflection at small source-detector separations
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Steady-state diffuse reflectance based on P3 approximation is studied at short source-detector separations. In many practical applications, we can only measure the diffuse reflectance light close to the source, and attempt to derive the optical parameters of tissues from the collected data. In this paper, diffuse refleSteady-state diffuse reflectance based on P3 approximation is studied at short source-detector separations. In many practical applications, we can only measure the diffuse reflectance light close to the source, and attempt to derive the optical parameters of tissues from the collected data. In this paper, diffuse reflectance with different absorption coefficients and scattering coefficients at short source-detector separations is measured, and the experimental results are compared with that of P3 approximation. These studies show that P3 approximation can be used to describe the light contribution close to the source, and can be used to study strong absorption medium..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 327 (2005)
Experiment study on laser generating the surface acoustic waves
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In the field of nondestructive evaluation, laser generation and detection of the surface acoustic waves (SAWs) are potentially useful for investigating material surfaces. SAW generated by laser line source is carried out on a kind of optical difference detection system based on optical beam deflection technique. The seIn the field of nondestructive evaluation, laser generation and detection of the surface acoustic waves (SAWs) are potentially useful for investigating material surfaces. SAW generated by laser line source is carried out on a kind of optical difference detection system based on optical beam deflection technique. The setup is simple and easy to adjust. Furthermore the system has advantages such as high efficiency of photo-electricity conversion, high frequency responding, the ability of ant-intervene and broadband detection etc.. It can be used not only to receive SAW, but also to detect surface-breaking defects in material. The experimental results verify that the SAWs generated by a line source have the advantages of powerful signal and good directivity. SAWs have been excited on sample aluminum with artificial surface-breaking defects. From the experiment, we attain the characters of reflected wave and transmitted wave by SAW interacted with the surface-breaking defects..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 329 (2005)
Numerical simulation of laser ultrasound detection of small defect in metal plates
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In order to further confirm the relations between the size of internal defect and the measured ultrasonic signals and understand the interaction mechanism between the ultrasonic wave and inside defect, this paper has constructed the two-dimensional (2D) plane strain finite element model of the Al plate with the inside In order to further confirm the relations between the size of internal defect and the measured ultrasonic signals and understand the interaction mechanism between the ultrasonic wave and inside defect, this paper has constructed the two-dimensional (2D) plane strain finite element model of the Al plate with the inside defect to simulate the scattering process of the ultrasonic wave generated by the pulsed laser in the Al specimen. The dependence of the normalized amplitude of the defect signal on the defect diameter has been calculated in details, and the ultrasonic reflectance by the cylindrical shaped internal defect was evaluated in details using the numerical results. It is demonstrated that the laser ultrasonic technique has the ability to detect the sub-millimeter-scale internal defects in industrial components and engineering structures..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 332 (2005)
Numerical simulation of the ultrasonic waves generated by ring-shaped laser illumination
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The improvement of the generation efficiency has attracted much attention, confronted with the little amplitude of acoustic wave generated by pulsed laser in the thermoelastic regime. This paper constructed the finite element model to simulate ultrasonic waves generated by the ring-shaped laser source with the 8 mm innThe improvement of the generation efficiency has attracted much attention, confronted with the little amplitude of acoustic wave generated by pulsed laser in the thermoelastic regime. This paper constructed the finite element model to simulate ultrasonic waves generated by the ring-shaped laser source with the 8 mm inner radii. The numerical results demonstrate that strong focusing exists at the center axis of ring as the result of constructive interference of the waves generated by different parts of the source. Furthermore, the bulk wave includes compression, shear peak amplitudes and the surface acoustic wave magnitude drops quickly when the receiver position is away from the epicenter. Numerical simulations indicated that the low acoustic amplitudes in laser acoustics can be relieved somewhat by taking advantage of constructive interference between waves generated by different parts of an acoustic source, giving locally higher amplitude..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 335 (2005)
Measuring ultrashort optical pulses using multi-shot second harmonic generation frequency resolved optical gating
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Frequency resolved optical gating (FROG), is an effective technique for characterizing the ultrafast laser pulses. The multi-shot second harmonic generation (SHG) FROG is the most sensitive one in different FROGs. In this paper we use this technique to measure the femtosecond optical pulses generated by a conventional Frequency resolved optical gating (FROG), is an effective technique for characterizing the ultrafast laser pulses. The multi-shot second harmonic generation (SHG) FROG is the most sensitive one in different FROGs. In this paper we use this technique to measure the femtosecond optical pulses generated by a conventional Ti:sapphire oscillator..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 338 (2005)
Study of fluorescence spectra of starch suspension excited by 260-nm UV light
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To achieve detection, monitoring, and automation of starch graft copolymerzation at any time, the investigation is being made according to luminescence of free radicals produced in the reaction. The investigations on the fluorescence spectra of starch-water suspension excited by ultraviolet (UV) light and its characterTo achieve detection, monitoring, and automation of starch graft copolymerzation at any time, the investigation is being made according to luminescence of free radicals produced in the reaction. The investigations on the fluorescence spectra of starch-water suspension excited by ultraviolet (UV) light and its characteristics contribute to study the characteristics and mechanisms of free radicals coming into being, emitting, and disappearing. Fluorescence spectra of starch, dextrose, sucrose, and maltose excited by 260-nm light are compared and their similarities further verify that this fluorescence comes from the transition from nonbonding, namely n electrons in the hetero-atom (O) of the functional group (C-O-C) called ether linkage, to the antibonding orbital 'sigma'*. The functional group is a part of six-membered ring structure in starch molecule. Meanwhile, the experimental results indicate that relative peak intensity of fluorescence emitted by 1% starch suspension comes to climax when starch suspensions with different concentrations are excited by the same wavelength..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 340 (2005)
Design of novel broadband electro-optic modulator
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The electro-optic modulator with the novel structure combining ridge structure and T-type electrode is given. Integrating T-type electrode structure and ridge wave guide structure should realize phase velocity matching, reduce effectively electrode loss and improve the performance and bandwidth of the modulator. The deThe electro-optic modulator with the novel structure combining ridge structure and T-type electrode is given. Integrating T-type electrode structure and ridge wave guide structure should realize phase velocity matching, reduce effectively electrode loss and improve the performance and bandwidth of the modulator. The design structure is analyzed and optimized by the finite-element method..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 343 (2005)
Monte Carlo modelling of OCT with finite-size-spot photon beam
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Infinitely narrow photon beams have been used in the former Monte Carlo modelling about the signal of optical coherence tomography (OCT). However, the focused spot size is finite and determined by the center wavelength of the optical source. In the present paper, finite-size photon beams are launched into a multi-layerInfinitely narrow photon beams have been used in the former Monte Carlo modelling about the signal of optical coherence tomography (OCT). However, the focused spot size is finite and determined by the center wavelength of the optical source. In the present paper, finite-size photon beams are launched into a multi-layer numerical phantom, and the signals of OCT are obtained based on Monte Carlo technique and Mie theory. By use of the model we confirm the shower curtain effect as researchers have found before..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 346 (2005)
Bragg grating spectra in a multimode optical fiber
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The mode coupling in multimode fiber Bragg gratings (MMFBGs) is analyzed by using the coupled-mode theory. The reflection spectra of MMFBGs excited by one mode and two modes are simulated. The results of the calculation show that MMFBGs have multiple reflection peaks due to the coupling between the same modes in counteThe mode coupling in multimode fiber Bragg gratings (MMFBGs) is analyzed by using the coupled-mode theory. The reflection spectra of MMFBGs excited by one mode and two modes are simulated. The results of the calculation show that MMFBGs have multiple reflection peaks due to the coupling between the same modes in counter-propagating direction and the coupling between the adjacent modes in counter-propagating direction, and the spectra depend on excitation conditions of the bounded modes, such as mode power and mode number..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 348 (2005)
The study on the diffraction field distribution by photomultiplier
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The diffractive field distributions of the dark edge on the negative, the edge of the knife and the single edge of the wire were investigated using photo-multiplier system. The results show that the new diffractive formula with the parameters describing the property of the edge of the diffractive object should be estabThe diffractive field distributions of the dark edge on the negative, the edge of the knife and the single edge of the wire were investigated using photo-multiplier system. The results show that the new diffractive formula with the parameters describing the property of the edge of the diffractive object should be established and that the property of the object may be realized by the investigation of the weak diffractive field distribution of the object..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 350 (2005)
Second-order solution of diffusion equation in multiple-scattering media with photon density wave
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The solution of the diffusion equation in multiple-scattering media with photon density wave is investigated and expanded in the theoretical aspect. A second-order analytical solution of diffusion equation in semi-infinite cube space with photon density was researched. Because the flux is the general measure value, andThe solution of the diffusion equation in multiple-scattering media with photon density wave is investigated and expanded in the theoretical aspect. A second-order analytical solution of diffusion equation in semi-infinite cube space with photon density was researched. Because the flux is the general measure value, and then the relationship between 'delta''mu'_(a) and flux Jn is obtained. The relative error between second-order and first-order was presented by the light flux. It is shown that second-order solution is more precise than first-order solution in computation, and the computational precision is more increase especially around the abnormal body. The more accurate theory contributes to the image reconstruction and the quality improvement in imaging..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 351 (2005)
Slowdown the light speed in an alexandrite crystal
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We have observed a hole in the absorption profile of the homogeneously broadened absorption band of an Alexandrite crystal. With the spectral hole-burning technique that resulting from the periodic modulation of the ground state population at the beat frequency between the pump and the probe fields, we observed the sloWe have observed a hole in the absorption profile of the homogeneously broadened absorption band of an Alexandrite crystal. With the spectral hole-burning technique that resulting from the periodic modulation of the ground state population at the beat frequency between the pump and the probe fields, we observed the slowdown the light propagation with the group velocity as slow as 12.5 m/s at room temperature. And the group velocity in the Alexandrite crystal depends on the amplitude modulation frequency, the power of laser beam and the orientation of the crystal lattice. The lower frequency or higher power leads to slower group velocity of light..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 354 (2005)
Wavefront measurement of double-clad pulsed ytterbium fiber laser
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Because of high efficiencies, compact structure, and excellent heat dissipation, high-power fiber lasers are extremely useful for applications such as cutting, welding, precision drilling, trimming, sensing, optical transmitter, material processing, micromachining, and so on. However, the wavefront of the double clad fBecause of high efficiencies, compact structure, and excellent heat dissipation, high-power fiber lasers are extremely useful for applications such as cutting, welding, precision drilling, trimming, sensing, optical transmitter, material processing, micromachining, and so on. However, the wavefront of the double clad fiber laser doped with ytterbium is still unknown. In this paper, wavefront of a fiber laser is measured and the traditional Hartmann-shack wavefront sensing method is adopted. We measured a double clad fiber laser doped with ytterbium which produces pulse wave output at infrared wavelength. The wavefront shape and contour are reconstructed and the result shows that wavefront is slightly focused and not an ideal plane wavefront. Wavefront measurement of fiber laser will be useful to improving the lasers' performance and developing the coherent technique for its applications..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 356 (2005)
FDTD analysis of Talbot effect of a high density grating
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Talbot effect of a grating with different flaws is analyzed with the finite-difference time-domain (FDTD) method. The FDTD method can show the exact near-field distribution of different flaws in a high-density grating, which is impossible to obtain with the conventional Fourier transform method. The numerical results iTalbot effect of a grating with different flaws is analyzed with the finite-difference time-domain (FDTD) method. The FDTD method can show the exact near-field distribution of different flaws in a high-density grating, which is impossible to obtain with the conventional Fourier transform method. The numerical results indicate that if a grating is perfect, its Talbot imaging should also be perfect; if the grating is distorted, its Talbot imaging would also be distorted. Furthermore, we can evaluate high density gratings by detecting the near-field distribution..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 358 (2005)
Gas content effect on bubble motion
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The gas content is one of the important bubble parameters. In this article, the gas content effect on the bubble motion is investigated by numerical simulation based on the spherical bubble model. The dependence of the bubble radius, oscillation velocity and the corresponding bubble energy on the gas content during theThe gas content is one of the important bubble parameters. In this article, the gas content effect on the bubble motion is investigated by numerical simulation based on the spherical bubble model. The dependence of the bubble radius, oscillation velocity and the corresponding bubble energy on the gas content during the bubble pulsation is analyzed in detail according to differential equations of the bubble dynamics. The numerical calculations are shown that with the gas content remained in a cavity increasing, the corresponding bubble radii become larger. Further, both the maximum bubble radius and bubble energy show approximately linear-relation with the gas content during the first oscillation cycle, while in the second pulsation period they are observed non-linear with the gas content. In addition, with the gas content increasing, the bubble expanding and contracting velocities are both decreased, whereas the corresponding oscillation periods at the first two oscillations are obviously prolonged..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 361 (2005)
Simulation of laser induced ultrasound in metals by mass spring lattice model
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Laser generated ultrasonic waves is numerically simulated by mass spring lattice model by considering the laser illumination as a vertical force, which is valid in the ablation regime. Few surface acoustic wave modes including surface skimming longitudinal wave, surface skimming shear wave, and Rayleigh-like wave are rLaser generated ultrasonic waves is numerically simulated by mass spring lattice model by considering the laser illumination as a vertical force, which is valid in the ablation regime. Few surface acoustic wave modes including surface skimming longitudinal wave, surface skimming shear wave, and Rayleigh-like wave are recorded in aluminum and copper plates. The results indicate that the excitation efficiency of ultrasound in aluminum plate is higher than that in copper plate. The normal component of the displacement at the epicenter has only the longitudinal wave mode and the shear wave mode appears wthen the detection position has a deviation from the epicenter. In addition, the amplitude increases and the arrive time delays with the deviation distance..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 364 (2005)
Study of acoustic wave generated by Q-switched laser on derma
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To study characteristics of acoustic wave generated by Q-switched laser on dermal pigmented lesions, pieces of derma peeled from a cavy's body are plucked their hair. The pieces of derma are radiated by Q-switched laser with different energy intensities. Momentary signals of acoustic wave generated by the Q-switcheTo study characteristics of acoustic wave generated by Q-switched laser on dermal pigmented lesions, pieces of derma peeled from a cavy's body are plucked their hair. The pieces of derma are radiated by Q-switched laser with different energy intensities. Momentary signals of acoustic wave generated by the Q-switched pulsed laser on dermal pieces are detected isochronously with sensors connected to a multi-channel digital oscilloscope. The signal data are analyzed with a personal computor. Clear signal curves of acoustic waves are obtained in the experiment. The amplitudes of the signals present the positive correlation with the energy intensity of the single pulse laser. The acoustic wave signals have practical meanings of reference to the real-time control of laser energy intensity in the course of the therapy of Q-switched laser on dermal pigmented lesions..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 366 (2005)
Study on the oscillation property of laser-produced cavitation bubbles in water
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In this paper, by means of a high-sensitive optical beam deflection technique combined with electrical delay technique, shock wave and cavitation effects by laser ablation of a metal in water are investigated in detail. The system is quite handy, and of high time resolving ratio and spactial precision. The experimentalIn this paper, by means of a high-sensitive optical beam deflection technique combined with electrical delay technique, shock wave and cavitation effects by laser ablation of a metal in water are investigated in detail. The system is quite handy, and of high time resolving ratio and spactial precision. The experimental results present the propagation of shock waves, the expansion and contraction of laser-induced cavitation bubble in the vicinity of a solid boundary, the maximum and minimum radii during the first two oscillating cycles and the corresponding pulsation durations, the formation and development of bubble-collapse-induced shock waves. With the increase of oscillating cycles, the maximum bubble radii are decreased sharply, as well as the corresponding expanding and contracting durations. The minimum bubble radius at the first oscillation is larger than that of the second. Besides, the duration of bubble expansion is obviously longer than that of contraction at the same oscillating cycle..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 369 (2005)
Experimental study on laser-induced plasma shock waves in transparent solid media
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By means of an optical fiber sensor based on beam deflection technique, the laser-induced plasma shock waves propagating in transparent organic glass are systemically investigated in experiments. Under the condition of free attenuation of shock wave, the temporal and spatial variations of some important parameters on tBy means of an optical fiber sensor based on beam deflection technique, the laser-induced plasma shock waves propagating in transparent organic glass are systemically investigated in experiments. Under the condition of free attenuation of shock wave, the temporal and spatial variations of some important parameters on the shock fronts are obtained by analyzing the experimental data. The experimental results reveal that shock waves, in the same medium, attenuate more slowly with the increase of laser energy; at the same time, propagation distance of shock waves increase when they have changed into sound waves..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 372 (2005)
High intensity infrared radiation system for medical application
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According to the geometry optical principles, a high intensity infrared radiation system for medical application is designed. In this system, the infrared optical fiber's output energy density can reach 17 kW/cm2 after being focused, and the diameter of the focus light spot is 0.3 mm. Thus, the system can be widelyAccording to the geometry optical principles, a high intensity infrared radiation system for medical application is designed. In this system, the infrared optical fiber's output energy density can reach 17 kW/cm2 after being focused, and the diameter of the focus light spot is 0.3 mm. Thus, the system can be widely used in different kinds of medical applications..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 3, Issue 0s, 375 (2005)
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