Journals >Chinese Optics Letters
Contents
2006
Volume: 4 Issue 11
20 Article(s)
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Research Article
Modular interference characteristic of two-mode fiber
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The modular interference characteristics of circular-core and elliptical-core two-mode fibers are investigated in theory. The intensity distribution and figure of two-lobe mode patterns are evaluated and simulated quantitatively for different phase difference change between LP01 and LP11^(even) mode. The interference mThe modular interference characteristics of circular-core and elliptical-core two-mode fibers are investigated in theory. The intensity distribution and figure of two-lobe mode patterns are evaluated and simulated quantitatively for different phase difference change between LP01 and LP11^(even) mode. The interference mode patterns of elliptical-core and circular-core two-mode fibers are compared, the result shows that the two-lobe interference patterns of the two-mode fibers generate energy exchange and oscillation, and the difference is that the interference mode patterns of circular-core two-mode fiber are almost elliptical, while the interference mode pattern of elliptical-core two-mode fiber is approximately circular on condition that proper selection of the ellipticity. Their two-dimensional (2D) profile determines the choice of the core shape of the information pick-up fiber..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 621 (2006)
A novel design for broadband dispersion compensation microstructure fiber
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A novel microstructure fiber (MF) structure is proposed for broadband dispersion compensation. Through manipulating the four air-hole parameters and the pitch, the broad band dispersion compensation MF can be efficiently designed. The newly designed MF could compensate (to within 0.8%) the dispersion of 101 times of itA novel microstructure fiber (MF) structure is proposed for broadband dispersion compensation. Through manipulating the four air-hole parameters and the pitch, the broad band dispersion compensation MF can be efficiently designed. The newly designed MF could compensate (to within 0.8%) the dispersion of 101 times of its length of standard single mode fiber over the entire 100-nm band centered on 1550 nm. The proposed design has been simulated through the finite difference beam propagation method, and the corresponding design procedures are also presented..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 625 (2006)
Controllable optical delay line using a Brillouin optical fiber ring laser
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A controllable optical delay line using a Brillouin optical fiber ring laser is demonstrated and a large time delay is obtained by cascading two optical fiber segments. In experiment, a single-mode Brillouin optical fiber ring laser is used to provide Stokes wave as probe wave. We achieve a maximum tunable time delay oA controllable optical delay line using a Brillouin optical fiber ring laser is demonstrated and a large time delay is obtained by cascading two optical fiber segments. In experiment, a single-mode Brillouin optical fiber ring laser is used to provide Stokes wave as probe wave. We achieve a maximum tunable time delay of 61 ns using two cascading optical fiber segments, about 1.5 times of the input probe pulse width of 40 ns. In the meantime, a considerable pulse broadening is observed, which agrees well with the theoretical prediction based on linear theory..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 628 (2006)
Application of two-mode fiber in voltage sensor
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A new mode pattern's demodulation technique is put forward. Researches of experiment and theory show that the coupling efficiency of two kinds of different fibers depends on the relative offset between the two fibers when the core diameter of the information pick-up fiber is a little smaller than the major semi-axeA new mode pattern's demodulation technique is put forward. Researches of experiment and theory show that the coupling efficiency of two kinds of different fibers depends on the relative offset between the two fibers when the core diameter of the information pick-up fiber is a little smaller than the major semi-axes of the elliptical-core two-mode fiber. Especially, when the relative offset 'delta' is about 1, fusing splice coupling efficiency reaches peak value. Furthermore, based on the new demodulation scheme, the sine voltage signal applied on the piezoelectric lead zirconate titanate (PZT) is obtained and the detection precision of the system is within +-0.2% when the voltage changes between 0.1 and 20 V..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 631 (2006)
Multipath dispersion of pulse signals in a non-line-of-sight optical scattering channel
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Multipath-induced pulse broadening in a non-line-of-sight (NLOS) optical scattering channel is investigated. Expressions for impulse response and digital signal-to-noise ratio (DSNR) penalty induced by intersymbol interference (ISI) of a NLOS ultraviolet (UV) scattering communication are introduced based on a single-scMultipath-induced pulse broadening in a non-line-of-sight (NLOS) optical scattering channel is investigated. Expressions for impulse response and digital signal-to-noise ratio (DSNR) penalty induced by intersymbol interference (ISI) of a NLOS ultraviolet (UV) scattering communication are introduced based on a single-scattering model, and simulated results for some typical atmospheric condition and configuration of geometry are given in the paper. It is shown that the multipath dispersion is one of the most important factors limiting the system performances, and return-to-zero (RZ) format is more suitable for the optical scattering communications than non-return-to-zero (NRZ) format. The method proposed here can be used to predict available bandwidth and data rate of the communication system operating in a NLOS optical scattering channel..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 633 (2006)
Low noise gain-clamped L-band erbium-doped fiber amplifier by utilizing fiber Bragg grating
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A novel gain-clamped long wavelength band (L-band) erbium-doped fiber amplifier (EDFA) is proposed and experimented by using a fiber Bragg grating (FBG) at the input end of the amplifier. This design provides a good gain clamping and decreases noise effectively. It uses two sections of erbium-doped fiber (EDF) pumped bA novel gain-clamped long wavelength band (L-band) erbium-doped fiber amplifier (EDFA) is proposed and experimented by using a fiber Bragg grating (FBG) at the input end of the amplifier. This design provides a good gain clamping and decreases noise effectively. It uses two sections of erbium-doped fiber (EDF) pumped by a 1480-nm laser diode (LD) for higher efficiency and lower noise figure (NF). The gain is clamped at 23 dB with a variation of 0.5 dB from input signal power of -30 to -8 dBm for 1589 nm and NF below 5 dB is obtained. At the longer wavelength in L-band higher gain is also obtained and the gain is clamped at 16 dB for 1614 nm effectively. Because the FBG injects a portion of backward amplified spontaneous emission (ASE) back into the system, the gain enhances 5 dB with inputting small signal..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 636 (2006)
Efficient image segmentation method based on resolution and region information fusion
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A generalized multiresolution likelihood ratio (GMLR), which can increase the distinction between different signals by fusing their more features, is defined. Multiresolution representation of image characterizes inherent structure of image well, and the GMLR combines each resolution image features with corresponding rA generalized multiresolution likelihood ratio (GMLR), which can increase the distinction between different signals by fusing their more features, is defined. Multiresolution representation of image characterizes inherent structure of image well, and the GMLR combines each resolution image features with corresponding region features. A spatially variant mixture multiscale autoregressive prediction (SVMMARP) model is proposed to estimate the parameters of GMLR based on maximum likelihood estimation via expectation maximization (EM) algorithm. In the parameter estimation, bootstrap sampling technique is employed. Experimental results demonstrate that the algorithm performs fairly well..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 639 (2006)
Optical E-field probe using LiNbO3 M-Z waveguides in the electromagnetic compatibility measurements
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An integrated optical E-field probe with the segmented electrode using LiNbO3 Mach-Zehnder (M-Z) waveguides is proposed and an equivalent circuit of the segmented electrode is given. According to the circuit theory, the electrode structure of the probe is designed. The unpackaged size of the fabricated probe is as smalAn integrated optical E-field probe with the segmented electrode using LiNbO3 Mach-Zehnder (M-Z) waveguides is proposed and an equivalent circuit of the segmented electrode is given. According to the circuit theory, the electrode structure of the probe is designed. The unpackaged size of the fabricated probe is as small as 60*6*0.5 (mm). The measured results show that the half wavelength voltage is 7.7 V, the +-5 dB baseband range is 3 GHz, and the minimum detectable field is lower than 90 dB*microV/m (bandwidth 100 Hz). Therefore it can be used in the electromagnetic compatibility (EMC) measurements..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 643 (2006)
An efficient intracavity-pumped KTP optical parametric oscillator at 1572 nm
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We demonstrate an efficient and eye-safe wavelength intracavity optical parametric oscillator (OPO), based on a KTP crystal inside a Q-switched Nd:YVO4 laser end pumped by a fiber-coupled diode laser. In the acousto-optic Q-switched operation with the pulse repetition rate of 10 kHz, a 1572-nm eye-safe laser with the aWe demonstrate an efficient and eye-safe wavelength intracavity optical parametric oscillator (OPO), based on a KTP crystal inside a Q-switched Nd:YVO4 laser end pumped by a fiber-coupled diode laser. In the acousto-optic Q-switched operation with the pulse repetition rate of 10 kHz, a 1572-nm eye-safe laser with the average power of 237 mW at the incident pump power of 5.64 W is obtained. Under the pulse repetition rate of 5 kHz, the signal light with pulse width of 2 ns and peak power of 18.5 kW is achieved. The conversion efficiency of the average power is 4.2% from pump diode to OPO signal output and the signal pulse duration is about 13 times shorter than that of the depleted pump light..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 646 (2006)
Free-running emerald laser pumped by laser diode
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Free-running emerald laser pumped by 660-nm laser diode (LD) was reported. Free-running output power of 24 mW has been obtained with overall efficiency of 1.4% and slope efficiency of 11.9% when the LD incident power was 2.56 W. The laser threshold value of emerald crystal was estimated to be 0.7 W.Free-running emerald laser pumped by 660-nm laser diode (LD) was reported. Free-running output power of 24 mW has been obtained with overall efficiency of 1.4% and slope efficiency of 11.9% when the LD incident power was 2.56 W. The laser threshold value of emerald crystal was estimated to be 0.7 W..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 649 (2006)
Multi-wavelength hybrid gain fiber ring laser based on Raman and erbium-doped fiber
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A stable and uniform multi-wavelength fiber laser based on the hybrid gain of a dispersion compensating fiber as the Raman gain medium and an erbium-doped fiber (EDF) is introduced. The gain competition effects in the fiber Raman amplification (FRA) and EDF amplification are analyzed and compared experimentally. The FRA stable and uniform multi-wavelength fiber laser based on the hybrid gain of a dispersion compensating fiber as the Raman gain medium and an erbium-doped fiber (EDF) is introduced. The gain competition effects in the fiber Raman amplification (FRA) and EDF amplification are analyzed and compared experimentally. The FRA gain mechanism can suppress the gain competition effectively and make the present multi-wavelength laser stable at room temperature. The hybrid gain medium can also increase the lasing bandwidth compared with a pure EDF laser, and improve the power conversion efficiency compared with a pure fiber Raman laser..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 652 (2006)
Dual-wavelength stable nanosecond pulses generation from cladding-pumped fiber laser
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In this paper, the generation of dual-wavelength stable nanosecond pulses by a laser diode pumped Yb-doped double-clad fiber laser is presented. In the experiment, the fiber laser with two-mirror cavity is approved which operates in a self-Q-switching regime. The Q-switching mechanism is based on stimulated Brillouin sIn this paper, the generation of dual-wavelength stable nanosecond pulses by a laser diode pumped Yb-doped double-clad fiber laser is presented. In the experiment, the fiber laser with two-mirror cavity is approved which operates in a self-Q-switching regime. The Q-switching mechanism is based on stimulated Brillouin scattering (SBS). When the pump power achieves the SBS threshold, the fiber laser changes from the start resonator to the SBS resonator. With different reflectivities of the second mirror, stable dual-wavelength pulses with the pulse width range from 10 ns to less than 2 ns are obtained. The result was explained theoretically by birefringency (including stochastic birefringency and bend birefringency)..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 655 (2006)
Investigation of laser diode face-pumped high average power heat capacity laser
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The three-dimensional (3D) pump intensity distribution in medium of the laser diode (LD) pumped high average power heat capacity laser is simulated by the ray tracing method, and the divergence characteristics of fast axis and slow axis of LD are simultaneously considered. The transient 3D temperature and stress distriThe three-dimensional (3D) pump intensity distribution in medium of the laser diode (LD) pumped high average power heat capacity laser is simulated by the ray tracing method, and the divergence characteristics of fast axis and slow axis of LD are simultaneously considered. The transient 3D temperature and stress distributions are also simulated by the finite element method (FEM) with considering the uneven heat source distribution in medium. A LD face-pumped Nd:GGG heat capacity laser is designed. The average output power is 1.49 kW with an optical-optical efficiency of 24.1%..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 658 (2006)
Photothermal damage prediction of laser interstitial thermotherapy
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An improved scattering optical model was developed under cylindrical coordinate to simulate the thermal effect of diffusing applicator in laser interstitial thermotherapy (LITT). The thermal damage was calculated by finite element method (FEM) using Pennes bio-heat transfer equation and Arrhenius injury integral formulAn improved scattering optical model was developed under cylindrical coordinate to simulate the thermal effect of diffusing applicator in laser interstitial thermotherapy (LITT). The thermal damage was calculated by finite element method (FEM) using Pennes bio-heat transfer equation and Arrhenius injury integral formula. The numerical results showed that the scattering can considerably influence the evaluation of the lesion area, and the relationship between application powers or time and resulting tissue thermal damage was nonlinear. Although usually applying relatively low power can avoid tissue charring, rather higher power is recommended because it is indispensable to achieve necessary damage threshold and the therapy time can be shortened..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 661 (2006)
Efficient intracavity optical parametric oscillator with diode side-pumped electro-optic Q-switched laser
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An efficient intracavity single-resonant optical parametric oscillator (OPO) at 1.571-micron eye-safe range using a non-critically phase-matched KTP crystal is reported. The OPO is excited by a diode side-pumped electro-optic Q-switched Nd:YAG laser at 1.064 microns. Signal pulse of 97 mJ and 3.56 ns is obtained under An efficient intracavity single-resonant optical parametric oscillator (OPO) at 1.571-micron eye-safe range using a non-critically phase-matched KTP crystal is reported. The OPO is excited by a diode side-pumped electro-optic Q-switched Nd:YAG laser at 1.064 microns. Signal pulse of 97 mJ and 3.56 ns is obtained under the input electric energy of 2.3 J, corresponding to a slope efficiency of 4.2%, and a repetition rate range of 1-30 Hz..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 664 (2006)
Revisit to the symmetry relations in diffusely backscattered polarization patterns of turbid media
As there exists an inconsistency in claiming the symmetrical relations in the 16 Mueller matrix elements used to describe a turbid medium, the author restudies the symmetrical relationships between diffusely backscattered polarization patterns in isotropic turbid media and simulates all two-dimensional elements of diffAs there exists an inconsistency in claiming the symmetrical relations in the 16 Mueller matrix elements used to describe a turbid medium, the author restudies the symmetrical relationships between diffusely backscattered polarization patterns in isotropic turbid media and simulates all two-dimensional elements of diffusely backscattered Mueller matrix in both cases of Rayleigh and Mie scatterings using the double-scattering approximation and the Monte Carlo algorithm, respectively. The previous experimental observations are compared with the numerically determined matrix elements, showing a good agreement in both double-scattering model and Monte Carlo simulation. The symmetrical relations between the Mueller matrix elements are clarified..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 667 (2006)
Design of the sample cell in near-field surface-enhanced Raman scattering by finite difference time domain method
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The rational design of the sample cell may improve the sensitivity of surface-enhanced Raman scattering (SERS) detection in a high degree. Finite difference time domain (FDTD) simulations of the configuration of Ag film-Ag particles illuminated by plane wave and evanescent wave are performed to provide physical insightThe rational design of the sample cell may improve the sensitivity of surface-enhanced Raman scattering (SERS) detection in a high degree. Finite difference time domain (FDTD) simulations of the configuration of Ag film-Ag particles illuminated by plane wave and evanescent wave are performed to provide physical insight for design of the sample cell. Numerical solutions indicate that the sample cell can provide more "hot spots'' and the massive field intensity enhancement occurs in these "hot spots''. More information on the nanometer character of the sample can be got because of gradient-field Raman (GFR) of evanescent wave..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 671 (2006)
Symmetrical periods used as matching layers in multilayer thin film design
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Properties of symmetrical layers as matching layers in multilayer thin film design were analyzed. A calculation method was presented to derive parameters of desired equivalent refractive index. A harmonic beam splitter was designed and fabricated to test this matching method.Properties of symmetrical layers as matching layers in multilayer thin film design were analyzed. A calculation method was presented to derive parameters of desired equivalent refractive index. A harmonic beam splitter was designed and fabricated to test this matching method..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 675 (2006)
Effects of oxygen partial pressure on optical properties of NiOx films deposited by reactive DC-magnetron sputtering
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The influence of oxygen partial pressure on the optical properties of NiOx thin films deposited by reactive DC-magnetron sputtering from a nickel metal target in a mixture gas of oxygen and argon was presented. With the oxygen ratio increasing, the reflectivity of the as-deposited films decreased, and optical band gap The influence of oxygen partial pressure on the optical properties of NiOx thin films deposited by reactive DC-magnetron sputtering from a nickel metal target in a mixture gas of oxygen and argon was presented. With the oxygen ratio increasing, the reflectivity of the as-deposited films decreased, and optical band gap increased. Thermogravimetric analysis (TGA) showed that the decompose temperature of the films was above 250 Celsius degrees. After annealed at 400 Celsius degrees, only films deposited at 5% O2/Ar ratio showed high optical contrast which was about 52%. Scanning electron microscope (SEM) results revealed that the changes of surface morphology were responsible for the optical property variations of the films after annealing. Its thermal stability and high optical contrast before and after annealing made it a good potential write-once optical recording medium..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 678 (2006)
Numerical simulation of isopachic parameter determined by phase-stepping interferometric photoelasticity: errata
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The authors regret that errors occurred in the previous paper (Chin. Opt. Lett. 4, 164. A phase-stepping interferometric photoelasticity method is proposed to determine whole-field sum of principal stresses. The four phase steps are introduced by rotating quarter-wave plate and analyzer at definite optical arrangementsThe authors regret that errors occurred in the previous paper (Chin. Opt. Lett. 4, 164. A phase-stepping interferometric photoelasticity method is proposed to determine whole-field sum of principal stresses. The four phase steps are introduced by rotating quarter-wave plate and analyzer at definite optical arrangements. Light intensities and phase-stepping formula for the proposed method are derived using Jones calculus. Simulations of a circular disk under diametral compression demonstrate the feasibility of the proposed method). This is the erratum to the errors..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 4, Issue 11, 682 (2006)
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