Journals >Acta Photonica Sinica
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2005
Volume: 34 Issue 8
40 Article(s)
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Research Article
The Research on Ce+:LiCaAlF6 Ultraviolet Laser
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A Ce∶LiCAF ultraviolet laser at 296 nm end-pumped by the fourth harmonic of Nd∶YAG laser with plano-concave resonator is reported. With the 20% transmission output coupler, the maximum output pulse energy of 270 μJ , the pulse width of 3.4 ns and the peak power of 79.4 kw are obtained at the incident pump energy of 13.A Ce∶LiCAF ultraviolet laser at 296 nm end-pumped by the fourth harmonic of Nd∶YAG laser with plano-concave resonator is reported. With the 20% transmission output coupler, the maximum output pulse energy of 270 μJ , the pulse width of 3.4 ns and the peak power of 79.4 kw are obtained at the incident pump energy of 13.5 mJ.The corresponding optical conversion efficiency and the average slope efficiency are calculated to be 2% and 1.6%, respectively..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1121 (2005)
Research on the Pulsed Laser Source with Multi-colors
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The femtosecond pulses produced by Ti∶sapphire mode-locked laser were applied as the pump light,to generate the supercontinuum light source in the polarization-maintaining photonic crystal fiber with the average core size of 1.8 μm due to its high nonlinear properties.The multi-colors laser light source in the visible The femtosecond pulses produced by Ti∶sapphire mode-locked laser were applied as the pump light,to generate the supercontinuum light source in the polarization-maintaining photonic crystal fiber with the average core size of 1.8 μm due to its high nonlinear properties.The multi-colors laser light source in the visible region with the central wavelengths of 431 nm, 497 nm, 520 nm, 575 nm, respectively, was achieved to be mW level with the adjusted coupling between the pump source and the photonic crystal fiber. And the output optical pulses were measured to be good stability with the same repetition rate of 250 kHz to the pump pulses..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1124 (2005)
Finite Element Analysis of Laser-Generated Rayleigh Wave Scattering by Cracks in a Plate
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The finite element method has been utilized to investigate the transient scattering of Rayleigh wave by a crack on a plate.The incident wave models and the guided waves generated by a pulsed line source are laser irradiation on the plate.Three surface-breaking cracks and three subsurface cracks are studied here.The resThe finite element method has been utilized to investigate the transient scattering of Rayleigh wave by a crack on a plate.The incident wave models and the guided waves generated by a pulsed line source are laser irradiation on the plate.Three surface-breaking cracks and three subsurface cracks are studied here.The results show that the location and the depth of cracks have measurable effects on the surface responses in time domains.The deeper surface-breaking crack will generate the more amplitude reflected wave,and the effect of the subsurface crack attributes to the vertical distance from the tip of subsurface crack to the top surface of the plate.Therefore,the waveform can be used to detect the surface breaking crack dimensions and the location position of the subsurface crack..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1128 (2005)
The Measurement of Polarization Mode Dispersion in Highly Birefringent Photonic Crystal Fiber
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The polarization mode dispersion in highly birefringent photonic crystal fiber is measured. In the experiment, the differential group delay of 108 ps was obtained by using a 26-meter-long PCF. Furthermore, PMD in this PCF has been measured by pulse delay method and fixed analyzer method. The result shows that the birefThe polarization mode dispersion in highly birefringent photonic crystal fiber is measured. In the experiment, the differential group delay of 108 ps was obtained by using a 26-meter-long PCF. Furthermore, PMD in this PCF has been measured by pulse delay method and fixed analyzer method. The result shows that the birefringence of the PCF is about 1.25×10 -3, and the high birefringent PCF can be used as dispersion compensation component in optical fiber communication system..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1133 (2005)
Analysis of Electroabsorption Modulators and Multimode Interference Splitters
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Based on the finite-differential beam propagation method and guided-mode analysis, the wave propagation characteristics of a AlGaAs/GaAs MQW electroabsorption modulator and multimode interference optical splitter are investigated. A novel wave-guide electroabsorption modulator incorporated with function of optical spliBased on the finite-differential beam propagation method and guided-mode analysis, the wave propagation characteristics of a AlGaAs/GaAs MQW electroabsorption modulator and multimode interference optical splitter are investigated. A novel wave-guide electroabsorption modulator incorporated with function of optical splitter is proposed and numerical simulated and experimental tested. The study results show that a wave-guide electroabsorption modulator with properly designed wave-guide thickness and length possesses features of optical splitter..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1137 (2005)
Improvement of Index Distributions for GRIN Lens by Two-step Ion-exchanging Method
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The two-step ion-exchanging method for fabrication of GRIN lens is proposed.The mixed salts of KNO~~3 and NaNO~~3 are used in the process of two-step ion-exchanging, and the result is satisfactory. The index distributions and aberrations are also measured. As a result, the index distributions are amended greatly and thThe two-step ion-exchanging method for fabrication of GRIN lens is proposed.The mixed salts of KNO_3 and NaNO_3 are used in the process of two-step ion-exchanging, and the result is satisfactory. The index distributions and aberrations are also measured. As a result, the index distributions are amended greatly and they are much more close to the ideal index distributions and the aberrations are decreased from 13.1% to 7.7%..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1141 (2005)
Improving the Efficiency of Organic Light-Emitting Devices with a Quinacridone Sub-Monolayer
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A Quinacridone(QAD) sub-monolayer was inserted in the Electron transporting layer of Organic Light-emitting Devices(OLEDs),which was used as a probe for excitons′ formation and diffusion.Tthe devices configuration are ITO/NPB(60 nm)/Alq~~3(x nm)/QAD(0.05 nm)/Alq~~3[(60-x)nm]/ LiF(0.4 nm)/Al(180 nm),of which x=0, 2.5, 5A Quinacridone(QAD) sub-monolayer was inserted in the Electron transporting layer of Organic Light-emitting Devices(OLEDs),which was used as a probe for excitons′ formation and diffusion.Tthe devices configuration are ITO/NPB(60 nm)/Alq_3(x nm)/QAD(0.05 nm)/Alq_3[(60-x)nm]/ LiF(0.4 nm)/Al(180 nm),of which x=0, 2.5, 5, 7.5 nm is the different position of deposited QAD sub-monolayer. The electroluminescence (EL) spectra and intensity of these four devices show that QAD sub-monolayer located at 5 nm apart from the NPB/Alq_3 heterojunction interface obtained excitons from Alq_3 at most through frster energy transfer.The comparison of the efficiency-operating voltage characteristics of the devices also indicate this result..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1145 (2005)
1/f Noise of GaAlAs IREDs Over a Wide Range of Bias Currents
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1/f noise in GaAlAs double hetero junction infrared ray LEDs (IRLEDs) is experimental and theoretical studied over a wide range of bias currents.Experimental results demonstrate that the magnitude of 1/f noise is in proportion to the bias current (IF) in the range below 3 mA,and tends to saturate when the current incre1/f noise in GaAlAs double hetero junction infrared ray LEDs (IRLEDs) is experimental and theoretical studied over a wide range of bias currents.Experimental results demonstrate that the magnitude of 1/f noise is in proportion to the bias current (IF) in the range below 3 mA,and tends to saturate when the current increases from 3 mA to 5 mA.While,in the current range above 5 mA,the magnitude of 1/f noise increases sharply and is proportional to I2F.Base on the mechanisms of carrier number fluctuations and carrier velocity fluctuations, a model for 1/f noise in GaAlAs IRLEDs is developed.It is discussed from the model that at small currents,1/f noise in GaAlAs IRLEDs comes from trapping and detrapping process between defects in the bulk region of devices (bulk defects) and carriers,which reveals characteristics of bulk defects.While,at large currents,it is due to fluctuations in the surface recombination velocity induced by the surface potential,which is modulated by oxide traps near the space-charge region, at these conditions,1/f noise reveals defects in the active region of devices (actives defects).1/f noise can be used as a sensitive and non-destructive reliability indicator to probe defects in different regions of GaAlAs IRLEDs..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1149 (2005)
Phase-shifting Technique and Iterative Technique Applied to SDF Joint Transform Correlator
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A phase-shifting joint transform correlator with synthetic discriminant function is obtained by use of the Gram-Schmidt expansion approach and iterative technique to recognize a class of objects.Compared with the SDF-based classical joint transform correlator,the phase-shifting joint transform correlator delivers a betA phase-shifting joint transform correlator with synthetic discriminant function is obtained by use of the Gram-Schmidt expansion approach and iterative technique to recognize a class of objects.Compared with the SDF-based classical joint transform correlator,the phase-shifting joint transform correlator delivers a better capability to give localized equal correlation peak heights for the same class of objects.The performance merits based on light efficiency and signal-to-clutter ratio are evaluated..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1153 (2005)
Quantization of Synthetic Discriminant Function Filter to a Quadrupole For Scale Invariant Pattern Recongition
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A new scale-invariant correlation filter based on synthetic-discriminant-function (SDF) was designed. In this filter, the correlation output function modulated by SDF in frequency-domian was quantized to complexes of a quaduploe to obtain sharp correlation peak. To satisfy the equal correlation peak criteria , an iteraA new scale-invariant correlation filter based on synthetic-discriminant-function (SDF) was designed. In this filter, the correlation output function modulated by SDF in frequency-domian was quantized to complexes of a quaduploe to obtain sharp correlation peak. To satisfy the equal correlation peak criteria , an iterative algorithm was utilized to modify the coefficients of SDF. Thus scale-invariant recognition was achieved. Computer simulation results show that the proposed method performs better compared with the basic SDF and the binary phase-only SDF(BPOF SDF) for the target images from training set..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1156 (2005)
Study on Compensation Relationships Among the Elements in Off-axis Three-mirror System
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The compensation relationships among the adjustable variables and those between surface errors and the adjustable variables in off-axis three-mirror system are analyzed. The decenter variable in the adjustable variables often brings the same kind of aberration as the position offset of the tilt variable does, so they aThe compensation relationships among the adjustable variables and those between surface errors and the adjustable variables in off-axis three-mirror system are analyzed. The decenter variable in the adjustable variables often brings the same kind of aberration as the position offset of the tilt variable does, so they are of considerable relativity. Based on the theory of offset aberration, the relationship between decenter variables and tilt variables is obtained by compensating the primary aberration caused by both the decenter variables and the tilt variables. The adjustable variables and surface errors are correlated by modeling the relationship between surface errors which is represented by Zernike polynomials and the primary aberration. The precondition of computer simulation for compensation is to adjust the decenter, tilt and transverse displacement of the optical elements when given a certain value of surface error. The result shows that the wave front performance degradation of compensated system is.
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1160 (2005)
A New Plane Array CCD Space Three-dimensional Photographic System
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A new plane array CCD space three-dimension photogrammetry system is described.The system can be applied to acquire three-dimensional image of moon surface. On the base of the primary TLS(three-line scanner),a new project was proposed,which uses an array CCD and wide-angle lens to achieve the effect of the common TLS. A new plane array CCD space three-dimension photogrammetry system is described.The system can be applied to acquire three-dimensional image of moon surface. On the base of the primary TLS(three-line scanner),a new project was proposed,which uses an array CCD and wide-angle lens to achieve the effect of the common TLS. And this new type of system have a lot of advantages compared with traditional TLS remote sensor, such as more simpler configurature, smaller size and more reliable stability. So it is very adapted to work in the space remote sensing environment..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1165 (2005)
Study of Polarized Characters of Stimulated Raman Scattering Spectrum in Single Mode Circlar Fiber
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The Raman threshold,frequency-shift and the states of Stokes spectrum of stimulated Raman scattering under the condition of different polarized pump light in single mode circle core optical fiber were studied. The polarization of pump and Stokes spectrum at output terminal of fiber were measured. The change of the polaThe Raman threshold,frequency-shift and the states of Stokes spectrum of stimulated Raman scattering under the condition of different polarized pump light in single mode circle core optical fiber were studied. The polarization of pump and Stokes spectrum at output terminal of fiber were measured. The change of the polarized light transmitted in single mode circle core optical fiber was analysed..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1169 (2005)
Measurement of the Nonlinear Refraction Index of Nd:YVO4 Crystal by Single-beam Z Scan
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In this measurement of the nonlinear refraction index of 4mm thick Nd∶YVO~~4 crystal, the single-beam Z scan method is employed and the experimental data is processed according to the Z scan theory of thin sample. As a result, the refraction index, which tallies with the one resulting from other different measure methoIn this measurement of the nonlinear refraction index of 4mm thick Nd∶YVO_4 crystal, the single-beam Z scan method is employed and the experimental data is processed according to the Z scan theory of thin sample. As a result, the refraction index, which tallies with the one resulting from other different measure method, is obtained in this measurement. So the rationality and the validity of this simple measurement and data processing method are proved..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1172 (2005)
A Circulated Demodulated Method of Distributed Fiber Raman Temperature Sensor
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In order to restrain the temperature excursion accumlation and Anti-Stokes back scattering intermingled with Rayleigh back scattering,a new type of demodulation method for distributed fiber Raman temperature sensor is proposed.By this method,which is named as circulated demodulated method(CDM),the Anti-Stokes optical tIn order to restrain the temperature excursion accumlation and Anti-Stokes back scattering intermingled with Rayleigh back scattering,a new type of demodulation method for distributed fiber Raman temperature sensor is proposed.By this method,which is named as circulated demodulated method(CDM),the Anti-Stokes optical time domain reflectance (OTDR) curves is demodulated by Rayleigh OTDR curves.The remedy increases the temperature precision,stability and sensitivity of system,reduces the cost of the system.The experiment results agree with the theory and the precision reaches at ±0.05℃..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1176 (2005)
Infrared Transmission Spectroscopy of B+ implanted HgCdTe Epilayers
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The calculation method of infrared transmission spectroscopy of boron-implanted HgCdTe epilayers was proposed based on multilayer model, transfer matrix and nonlinear least squares method. The results show that the transmission spectra of HgCdTe epilayers can be fitted very well by the theoretical calculation curves. BThe calculation method of infrared transmission spectroscopy of boron-implanted HgCdTe epilayers was proposed based on multilayer model, transfer matrix and nonlinear least squares method. The results show that the transmission spectra of HgCdTe epilayers can be fitted very well by the theoretical calculation curves. By fitting, the carrier concentration, the mobility, the sheet carrier concentration, the refractive index and the extinction coefficient in B+ implanted zone are obtained. These parameters are consistent with those obtained from different Hall measurement before. The effect of B+ implantation on the transmission spectra of HgCdTe epilayers mainly comes from the changes of the refractive index and the extinction coefficient of HgCeTe material in B+ implanted zone..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1179 (2005)
Experimental Investigation on Gas Concentration Measurement of Methane by LED
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In this paper, a differential measurement system of methane concentration by using LED as the light source is reported. The functions of each optical element in the system are carefully analyzed, and the calculation method and the experimental results of methane concentration are given. The R branch in 2ν~~3 spectral bIn this paper, a differential measurement system of methane concentration by using LED as the light source is reported. The functions of each optical element in the system are carefully analyzed, and the calculation method and the experimental results of methane concentration are given. The R branch in 2ν_3 spectral band are selected as the working spectral lines. A Fabry-Perot interferometer is used,and the transmission curve of the interferometer matches the absorption peaks of the methane at the working spectral lines.So that the useless light from the light source can be filtered out. The cavity length F-P interferometer is modulated by PZT, and the differential absorption measurement is realized. In this way, the measurement sensitivity is enhanced and a good result has been achieved..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1183 (2005)
Antireflective Thin Film Design Using ITO Material
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Usually, ITO transparent conductive thin film is made up of only one layer of ITO material with the mean transmittance of nearly 90% in the visible region of the spectrum. The results of using two different new design to produce antireflective film with ITO and deposition them by RLVIP technique are discussed.The mean Usually, ITO transparent conductive thin film is made up of only one layer of ITO material with the mean transmittance of nearly 90% in the visible region of the spectrum. The results of using two different new design to produce antireflective film with ITO and deposition them by RLVIP technique are discussed.The mean optical transmittance of thin film of T= 95.83%、the maximum transmittance of T_ max=97.26% and the sheet resistance of R_□=13.2～24.6Ω/□ are achieved by the design in experiments..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1187 (2005)
Research on All Optical Poling for the Organic Polymer PMMA Film Doped with Disperse Orange 25
Using disperse orange 25 as guest dye, the doped film sample of organic polymer PMMA was fabricated and all optical poled. The stronger the intensity of the two writing light beams correspond to the faster the second order susceptibility for the second nonlinear optical effect by the all optical poling achieves the satUsing disperse orange 25 as guest dye, the doped film sample of organic polymer PMMA was fabricated and all optical poled. The stronger the intensity of the two writing light beams correspond to the faster the second order susceptibility for the second nonlinear optical effect by the all optical poling achieves the saturation. The quality of the second nonlinear optical effect in the film was affected by several factors such as the difference between phases, the ratio of intensities of light beams, the ratio of intensity of optical fields of two writing beams..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1190 (2005)
Study on Transverse-load Characteristics and Polarization Dependence of Novel Long Period Fiber Gratings
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It is demonstrated that the transverse-load characteristic of the resonant wavelength for LPFGs induced by high-frequency CO~~2 laser pulses depends strongly on the load-direction, whereas the transverse-load characteristics of the loss peak amplitude is independent on the load-direction. The polarization dependence ofIt is demonstrated that the transverse-load characteristic of the resonant wavelength for LPFGs induced by high-frequency CO_2 laser pulses depends strongly on the load-direction, whereas the transverse-load characteristics of the loss peak amplitude is independent on the load-direction. The polarization dependence of the resonant wavelength for the LPFGs is deeply affected by the transverse-load, and the affection depends on load direction, whereas, the polarization dependence of the loss peak amplitude is little affected by the transverse-load. The transverse-load resulted in the optical-axis of the LPFG rotating. The unique transverse-load characteristics of the novel LPFG are analyzed using the theories about the optical-axis rotation, resulting from the load-induced birefringence, of the LPFG..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1195 (2005)
Theoretical Study of Single-photon Acquisition Based on Hermite-Gaussian Beams
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Single-photon acquisition probability is deduced from TEM~~ 10 and TEM~~ 01 mode Hermite-Gaussian beams of optical electromagnetic field equation. Single-photon acquisition is analyzed for the laser links between a ground station and a satellite in a low earth orbit. The theoretical study shows that it is feasible for Single-photon acquisition probability is deduced from TEM_ 10 and TEM_ 01 mode Hermite-Gaussian beams of optical electromagnetic field equation. Single-photon acquisition is analyzed for the laser links between a ground station and a satellite in a low earth orbit. The theoretical study shows that it is feasible for quantum key distribution between a ground station and a satellite in a low earth orbit to use highly attenuated laser pulses based on TEM_ 10 and TEM_ 01 mode Hermite-Gaussian beams as single-photon sources..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1201 (2005)
Applicability of the Focusing Method to Measure the Refractive Index Profile of Polymer Optical Fibers
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The possibility of applying the focusing method to measure the refractive index profile of polymer optical fibers is studied through combination of the theoretical analysis and experimental verification. The result shows that the focusing method is an easy and feasible way to determine the refractive index of graded-inThe possibility of applying the focusing method to measure the refractive index profile of polymer optical fibers is studied through combination of the theoretical analysis and experimental verification. The result shows that the focusing method is an easy and feasible way to determine the refractive index of graded-index POFs; however, as the light rays cross each other near the POF boundary, the focusing method is not an appropriate way to decide accurately the refractive index profile of step-index POFs..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1205 (2005)
A Novel Technique of Temperature Sensitivity Enhancement and Reflection Spectrum Improvement of Fiber Bragg Gratings
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A novel fiber grating temperature sensing technique and its experimental result is reported,which eliminates the chirped effects of polymer-packaged,improves the reflection spectrum of FBG and the technique of repeated packaged by using a kind of polymer-packaged with biggish thermal expansion coefficient and a specialA novel fiber grating temperature sensing technique and its experimental result is reported,which eliminates the chirped effects of polymer-packaged,improves the reflection spectrum of FBG and the technique of repeated packaged by using a kind of polymer-packaged with biggish thermal expansion coefficient and a special coupling agent. The experimental result indicates that ,within 30.6℃~120℃ ,the temperature sensitivity is 0.1173 nm/℃ and the resolution temperature measurement is <0.43℃,which are 11 times higher than that of the bare FBG and the most important advantage is that the reflection spectrum remains same in the whole test.The average temperature sensitivity multiple of polymer-packaged fiber Bragg gratings is γ′=10.34,which matches the theoretical multiple γ=10.76 well. The linearity of the temperature response curves is 0.9983..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1209 (2005)
Performance of DOP Technique Used to Control PMD Compensation
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Based on principal state of polarization (PSP) theory, an analytical expression of the degree of polarization (DOP) of optical signal is obtained. The effects of various factors on signal DOP degradation are presented by numerical simulation for 40 Gb/s optical transmission system. The results show that DOP technique iBased on principal state of polarization (PSP) theory, an analytical expression of the degree of polarization (DOP) of optical signal is obtained. The effects of various factors on signal DOP degradation are presented by numerical simulation for 40 Gb/s optical transmission system. The results show that DOP technique is able to effectively monitor and control polarization mode dispersion (PMD) compensation of 40 Gb/s optical transmission system with the different group delay (DGD) less than 37.5 ps. Furthermore, an optimal pulse width is found with regard to maximizing the tolerable DGD range,which is 1/e-intensity half width equal to 0.45 bit period (11.25 ps)..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1213 (2005)
A Scheme of Multi-wavelength OCDMA Decoder and Its Performance Analysis
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A scheme of multi-wavelength OCDMA(MW OCDMA) decoder is proposed,which employs several optical hard-limiters to reduce multi-access interference(MAI).The performances of bit error rate (BER),spectral efficiency and normalized throughput are studied.The results show that BER of MW OCDMA system is improved by the scheme.A scheme of multi-wavelength OCDMA(MW OCDMA) decoder is proposed,which employs several optical hard-limiters to reduce multi-access interference(MAI).The performances of bit error rate (BER),spectral efficiency and normalized throughput are studied.The results show that BER of MW OCDMA system is improved by the scheme.Increasing the number of simultaneous users under a desired BER,spectral efficiency will also be improved.At the same time,optical hard-limiter can enhance the normalized throughput of MW OCDMA system.Especially the peak of normalized throughput is doubled..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1217 (2005)
A 3-D Digital Watermarking System Based on Virtual-Optics and Random Mask Encoding
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A new approach to digital watermarking in three-dimensional (3-D) space based on virtual-optics and random mask encoding is presented. The watermarking algorithm can offer an effective solution to the issue of copyright protection of multimedia data distributed via the communication channel.The results show that the emA new approach to digital watermarking in three-dimensional (3-D) space based on virtual-optics and random mask encoding is presented. The watermarking algorithm can offer an effective solution to the issue of copyright protection of multimedia data distributed via the communication channel.The results show that the embedded watermark is robust to normal data manipulations, such as adding noise, cropping, rotation, and JPEG compression. Because the design concept and methodology based on geometric parameters of Virtual-Optics was adopted, the proposed 3-D watermarking system has good security. There are large degrees of freedom existing for designing a security lock(s)/key(s), including multiple lock(s)/key(s) and multi-dimensional lock(s)/key(s). Numerical experiments are performed to validate the proposed method, and sensitivities of some parameters are quantitatively analyzed and illustrated. The possible dimensions of keys are roughly estimated and show a high security level..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1220 (2005)
Improving Iris Recognition by Multi-vanishing Moments Joint Best Basis Selection
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In digital computation, it is the discrete sampling sequences of continuous wavelet functions that are used. Using the cascade algorithm, the discrete approximating sequences of scaling and wavelet functions are computed for introducing the mother wavelets without analytical forms into iris feature extraction. By the dIn digital computation, it is the discrete sampling sequences of continuous wavelet functions that are used. Using the cascade algorithm, the discrete approximating sequences of scaling and wavelet functions are computed for introducing the mother wavelets without analytical forms into iris feature extraction. By the definition of wavelet packets, the discrete approximating sequences of wavelet packet functions can also be computed to fulfill continuous transform. Using continuous wavelet packet transform based on these sequences, the multi-vanishing moments joint best wavelet packet bases are chosen for eigen-images generation in the eigen-images based correlation recognition. This recognition is implemented by a volume holographic correlation system to take good use of high parallelism of optics. The modified post-processing method using statistic feature can make the algorithm more robust to the errors introduced in optical system. In simulation, with the high precision of digital computation, the identifi.
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1224 (2005)
Fabrication and Application of Photorefractive Multiple Volume Gratings
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Based on the filtering principle of photorefractive multiple volume gratings, superposition of eight volume gratings at the angle 0.037 degree between the grating wave vectors in the LiNbO~~3∶Fe crystal with size of 10×10×10 mm3 has been obtained by using incremental recording method. Those gratings have apprBased on the filtering principle of photorefractive multiple volume gratings, superposition of eight volume gratings at the angle 0.037 degree between the grating wave vectors in the LiNbO_3∶Fe crystal with size of 10×10×10 mm3 has been obtained by using incremental recording method. Those gratings have approximately the same diffraction efficiency. So the application of multiple volume gratings in wavelength demultiplexing system is demonstrated by the experiment. Furthermore, a double wavelength filter using the LiNbO_3∶Fe crystal has been made.Two light beams with the wavelength of 635 nm and 650 nm illuminating the volume gratings in the same direction have been separated by the filter successfully. According to the Bragg condition, the volume grating is used to measure the wavelength of light wave, and the measurement accuracy can reach the order of 10 pm..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1229 (2005)
Double-exposed Holographic Interferometry Diagnose in Microwave Plasma Thruster's Plume and Simulation by Computer
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Double-exposed holographic interferometry is an effective means in the plasma number density of electronic diagnosis, for it has such merits as non-contact measurement and non-disturbance by plasma luminescence. According to Abel transform, simulated interferograms of various plasma′s electron densities are obtained;byDouble-exposed holographic interferometry is an effective means in the plasma number density of electronic diagnosis, for it has such merits as non-contact measurement and non-disturbance by plasma luminescence. According to Abel transform, simulated interferograms of various plasma′s electron densities are obtained;by double-exposed holographic interferometry, interferograms of various spacecraft microwave plasma thruster′s plumes are gotten.The electron density of plume is gained by analyzing and contrasting the measured interferograms and simulated ones..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1233 (2005)
Growth of LiNbO3 Single Crystals Co-doped Fe and Zn by Bridgman Method and Their Emission Spectra
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Through the proper conditions such as feed materials with proper composition (Li~~2O 48.6 mol%, Nb~~2O~~5 51.4 mol%), growth rate of less than 3 mm/h, a temperature gradient of 20~40℃/cm across the solid-liquid interface and suitable gradient field of the whole furnace,LiNbO~~3 crystals co-doped with Cr 3+ ions in 0.1 Through the proper conditions such as feed materials with proper composition (Li_2O 48.6 mol%, Nb_2O_5 51.4 mol%), growth rate of less than 3 mm/h, a temperature gradient of 20~40℃/cm across the solid-liquid interface and suitable gradient field of the whole furnace,LiNbO_3 crystals co-doped with Cr 3+ ions in 0.1 mol% and Zn in 3 and 6 mol% can grow,respectively, by Bridgman method.The crystals without micro-defects are obtained, and there is no impurity center under the irradiation of He-Ne laser. The emission spectra between 700~1200 nm and the temperature-dependence emission spectra of R lines at 710~740 nm were measured. The observed R lines were attributed to the different Cr 3+ ion sites (Cr 3+_ Li and Cr 3+_ Nb) and the hot phonon-assistant absorption..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1237 (2005)
Simulation of the Optical Properties for the Perfect PbWO4 Single Crystal
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The electronic structure, dielectric function, complex reflectivity index and absorption spectra of the perfect PbWO~~4 crystal have been calculated using full-potential (linearized) augmented plane-wave ((L)APW) + local orbitals (lo) method.The peaks of the absorption spectra corresponding with electronic transition hThe electronic structure, dielectric function, complex reflectivity index and absorption spectra of the perfect PbWO_4 crystal have been calculated using full-potential (linearized) augmented plane-wave ((L)APW) + local orbitals (lo) method.The peaks of the absorption spectra corresponding with electronic transition have been studied. The calculated results indicate that the dielectric function, complex reflectivity index and absorption spectra of the crystal are related to the electronic structures of the crystal. Since the perfect PWO crystals do not occur absorption spectra in the visible region, the perfect PWO crystals are transparent crystals..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1241 (2005)
Omnidirectional Reflector of Combined One-dimensional Photonic Crystals
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Based on the photonic bandgap structures of one-dimensional photonic crystals,the method is optimized to make the constructed omnidirectional photonic bandgaps as large as possible,and the idiographic criteria of optimized models are proposed.The criteria are different depending on whether the one-dimensional photonic Based on the photonic bandgap structures of one-dimensional photonic crystals,the method is optimized to make the constructed omnidirectional photonic bandgaps as large as possible,and the idiographic criteria of optimized models are proposed.The criteria are different depending on whether the one-dimensional photonic crystals used in the method have their own omnidirectional photonic bandgaps or not.Then the formulae to quantitatively calculate the parameters involved in the criteria are derived.At last,a combined structure of four one-dimensional photonic crystals is calculated by using the transfer matrix method to check the criteria of combination,and get predicted results..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1245 (2005)
3-D Shape Measurement with Fourier Transform Based on LCD Projector
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With the digital shadow technology,reference image and deformed image are captured by CCD and saved in computer.Then the information of the object can be obtained through Fourier transform of the two images.The measurement has a high level of automation.Especially the fringes are sinusoidal patterns and the spatial linWith the digital shadow technology,reference image and deformed image are captured by CCD and saved in computer.Then the information of the object can be obtained through Fourier transform of the two images.The measurement has a high level of automation.Especially the fringes are sinusoidal patterns and the spatial line pitch can be optionally adjusted,which are more precious compared with the grating-projected fringes.The devices are common and the demand for environment is low.The results proved that the system has higher precision and further applications because of its simplicity..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1250 (2005)
Researches on the Measurement of Bubble Velocity Based on Cross-Correlation
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Through researching on the velocity vector of bubbly wall in the ship wake,the bubble movement character can be found out.Also,the research and realization of the ship wake self-guide torpedo is based upon this character.After comparing the differences between Cross-Correlation and Doppler method,the Cross-Correlation Through researching on the velocity vector of bubbly wall in the ship wake,the bubble movement character can be found out.Also,the research and realization of the ship wake self-guide torpedo is based upon this character.After comparing the differences between Cross-Correlation and Doppler method,the Cross-Correlation method has been applied to the measurement of bubbly wall parameters in ship wake from a new aspect.The high-speed CCD camera is used to acquire the images of simulating ship wake,the velocity of bubbles in the ship wake is computed from image post-processing. Through improving cross-correlation algorithm commonly used for analysis of flow field,the Fast Fourier Transform (FFT) has been used to compute the cross-correlation function rapidly.In order to enhance the computing accuracy,Gauss curve fitting is used to modify the location of the max value point,and the fitting formula is listed,so the bubble velocity with subpixel accuracy is obtained.In order to calibrate the algorithm,the image tran.
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1253 (2005)
A Novel Approach for Phase Demodulation from a Single Fringe Pattern
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A new technique for phase demodulation from a single fringe-pattern image is presented in this paper. The method locates the extremes of fringes′ intensity distribution,and converts the intermediate gray-values into values between -1 and 1 using linear interpolation. Based on the extremes map,a wrapped phase distributiA new technique for phase demodulation from a single fringe-pattern image is presented in this paper. The method locates the extremes of fringes′ intensity distribution,and converts the intermediate gray-values into values between -1 and 1 using linear interpolation. Based on the extremes map,a wrapped phase distribution is demodulated from a single fringe-pattern and the phase values are computed by using an arcos mode rather than the traditional atan2 mode.Through the new method, wrapped phase values can be efficiently extracted from a singgle fringe-pattern without the need of carrier fringers........
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1257 (2005)
Real-time Image Tracking Based on Adaptive Threshold in High Speed TV
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Based on the high speed TV,the obtainment of the self-adaptive threshold was introduced,which was very important to automatic target tracking.At the same time,the three tracking ways such as Center Tracking,Correlation Tracking and Integrate Tracking had been put forward,which could be used to track some given objects Based on the high speed TV,the obtainment of the self-adaptive threshold was introduced,which was very important to automatic target tracking.At the same time,the three tracking ways such as Center Tracking,Correlation Tracking and Integrate Tracking had been put forward,which could be used to track some given objects that likely had varied shape,abnormal acceleration and quite high speed.Experiments revealed that these tracking ways are stable,available and compatible with much reference and application value in the related field such as the design and realization of Automatic Target Tracking System in High-speed TV..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1262 (2005)
An Electronic Image Stabilization Method Based on Projection Algorithm
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An analysis of the causes of image motion is made and a research on the characteristics of the unwanted camera motion and the intentional camera movement is carried out.And then an EIS method based on projection algorithm PMCA is presented.Original estimated motion vectors are smoothed through a moving average filter.AAn analysis of the causes of image motion is made and a research on the characteristics of the unwanted camera motion and the intentional camera movement is carried out.And then an EIS method based on projection algorithm PMCA is presented.Original estimated motion vectors are smoothed through a moving average filter.An error propagation control method is used to prevent boundary error.Experimental results show that this algorithm can effectively smooth out the unwanted camera motion and follow the intentional camera movement..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1266 (2005)
Method of Stokes Images Calculation Based on Adaptive Unsubsample Lifting Scheme
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According to the principle and method of Stokes images′ calculation in imaging polarization detection,the shortcomings of traditional method in preserving detail information and dealing with the shifting of scene are analyzed.Then a new calculation method is proposed based on adaptive shift invariant wavelet. To make tAccording to the principle and method of Stokes images′ calculation in imaging polarization detection,the shortcomings of traditional method in preserving detail information and dealing with the shifting of scene are analyzed.Then a new calculation method is proposed based on adaptive shift invariant wavelet. To make the algorithm more flexible and fast,lifting scheme is used to perform wavelet transformation.The average,variance,entropy,and boundary energy are used to evaluate the performance of different calculation methods.Through simulation,the quality of Stokes′ images are improved by this paper′s algorithm,at the same time,this algorithm is insensitivity to shifting of scene in source image..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1270 (2005)
Managing of Wake Optical Signal
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The optical signals of wakes stimulated in laboratory are analyzed and calculated mainly by using MATLAB tools of filter,disperse Fourier transformation (DFT),and statistic semaphore managing etc.The optical semaphores with and without bubble film are much different on the point of energy.Filter can only be used to manThe optical signals of wakes stimulated in laboratory are analyzed and calculated mainly by using MATLAB tools of filter,disperse Fourier transformation (DFT),and statistic semaphore managing etc.The optical semaphores with and without bubble film are much different on the point of energy.Filter can only be used to manage the signals as pretreatment which needs to be treated more in order to practice.Results of DFT under various pressures are different that provide a clew for estimating wakes of different speed and age.By Chirp z transformation,which can provide visual graphs and a proper way to manage graphs,it is possible to confirm the characteristic of optical signals for detecting ship wakes..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1274 (2005)
Virtual Manufacturing and the Application on the Development of High-Speed Photograph Camera
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Virtual Manufacturing (VM) is a concept of executing manufacturing process in computers as well as in the real world,where virtual modes allow for prediction of potential problems for product functionality and manufacturability before real manufacturing occurs.As a new manufacturing technology,VM affects the whole manuVirtual Manufacturing (VM) is a concept of executing manufacturing process in computers as well as in the real world,where virtual modes allow for prediction of potential problems for product functionality and manufacturability before real manufacturing occurs.As a new manufacturing technology,VM affects the whole manufacturing industry including the manufacture of high-speed photograph camera (HSPC).The application of VM successfully resolves a series of technical difficulties caused by increasing photograph frequency of HSPC.These efforts of VM can not only increase the level and overall design quality of HSPC manufacturing,but also decrease the development cycle.At the same time,a new tool for key technology analysis and design solution in the field of HSPC manufacture is provided.For an example,a kind of HSPC is listed as follows.It has been studied in a virtual environment through the design,assembling,dynamic analysis and movement simulation procedures..
Acta Photonica Sinica
- Publication Date: Aug. 01, 2005
- Vol. 34, Issue 8, 1278 (2005)
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