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2012
Volume: 39 Issue 3
44 Article(s)
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Holography and Information Processing
Elemental Images Correction of Camera Array Pick-up for Three-Dimensional Integral Imaging
Jiao Xiaoxue, Zhao Xing, Yang Yong, Fang Zhiliang, and Yuan Xiaocong
A method is presented to correct the errors of elemental images due to position deviation of cameras in the process of camera array pick-up of three-dimensional (3D) integral imaging. By calculating position coordinates of reference points and position errors of camera array, the accuracy of correction algorithm and thA method is presented to correct the errors of elemental images due to position deviation of cameras in the process of camera array pick-up of three-dimensional (3D) integral imaging. By calculating position coordinates of reference points and position errors of camera array, the accuracy of correction algorithm and the relationship between position errors of camera array and elemental images are analyzed. Optical experimental results verify the feasibility of the proposed method. The results show that, the proposed method can effectively eliminate the effect of position deviation of camera array on the elemental images array and the reconstruction 3D images with better quality can be achieved after correction. The comparison of reconstruction 3D images before and after correction indicates that the errors of elemental images captured by camera array are corrected successfully with value of peak signal to noise ratio 33.6 percent improved, which can satisfy the display requirement of integral imaging..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 309001 (2012)
Experimental Study on Quantitative Phase Imaging by Digital Holographic Microscopy
Ma Lihong, Wang Hui, Jin Hongzhen, and Li Yong
Digital holographic microscopy apparatus with pre-magnification has been set up, which can well acquire the quantitative phase images for living biological specimens. In addition, a series of digital holograms can be automatically recorded and movies of holographic phase images of living biological specimens can be creDigital holographic microscopy apparatus with pre-magnification has been set up, which can well acquire the quantitative phase images for living biological specimens. In addition, a series of digital holograms can be automatically recorded and movies of holographic phase images of living biological specimens can be created. The accuracy of quantitative imaging is verified by a self-produced stepped transparent sample with known height and refraction. Onion epidermal cells and red blood cells are measured and quantitative high-quality phase images are obtained. The movies of phase images for paramecium are achieved. Experimental results demonstrate that the established system can achieve real-time quantitative high-resolution holographic phase image and can be effectively applied to living biological specimens phase imaging..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 309002 (2012)
Laser Manufacturing
Weld Penetration Depth Prediction of Pulsed Laser Welding Titanium Alloy Thin Plate
Zhang Jian, and Yang Rui
Depth of weld penetration is very important to laser welding quality. Laser welding is a complicated process, and quantitative analysis of this process is quite difficult. A set of TC4 titanium alloy thin plate specimens are used as laboratory samples. The acoustic signals are first preprocessed by the spectral subtracDepth of weld penetration is very important to laser welding quality. Laser welding is a complicated process, and quantitative analysis of this process is quite difficult. A set of TC4 titanium alloy thin plate specimens are used as laboratory samples. The acoustic signals are first preprocessed by the spectral subtraction noise reduction method and analyzed in both time and frequency domains, and a valid relationship between the acoustic signals and the weld penetration depth is deduced. Radial basis function neural network (RBFNN) models are developed to predict the weld penetration depth. Sound pressure deviation, band power, laser power and welding speed are used as input variables of RBFNN. The results show that the acoustic signal can characterize and predict the depth of weld penetration well under different laser welding parameters..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 303001 (2012)
Temperature Field Numerical Simulation of Laser Cladding Based on Internal Powder Feeding through a Hollow Laser Beam
Shi Shihong, Wang Chen, Xu Aiqin, Sun Houshun, and Li Hongyuan
A numerical simulation model of laser cladding based on internal powder feeding through a hollow laser beam is set up by Ansys parametric design language (APDL). The laser beam of cladding is a continuous motion ring form according to the process method of "hollow laser beam and internal powder feeding". TempA numerical simulation model of laser cladding based on internal powder feeding through a hollow laser beam is set up by Ansys parametric design language (APDL). The laser beam of cladding is a continuous motion ring form according to the process method of "hollow laser beam and internal powder feeding". Temperature distribution of laser cladding process can be got by model calculation. The calculation results show that, when the hollow laser beam is used, the highest temperature area of the molten pool is the saddle-shaped. In the base plate longitudinal section, the distribution of molten pool high temperature is asymmetrical "W" shape, and high temperature area mainly distributes behind the flare center. In base plate cross section, the distribution of molten pool high temperature is symmetrical "W" shape, the temperature of the molten pool center is low, and the both side temperature of the molten pool is high, thus the combination between cladding layer and base plate can be judged by the isothermal diagram. The temperature in the center of laser scanning undergoes twice sharp quenching and snap heat processes. It goes up and down rapidly first, and then goes up and down again. The second rising temperature is higher than the first one during the scanning. The temperature on both edges of the scanning tracks has only once sharp quenching and snap heat process, and the distribution of temperature is more uniform..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 303002 (2012)
Theoretical Model of Singly-Scattered Laser-Induced Ultrasound in Weak-Scattering Materials
Xu Baiqiang, Yang Xiaoping, Xu Guidong, Xu Chenguang, Chen Anqi, and Liu Hongkai
Based on the diffuse wave transfer theory, a theoretical model of singly-scattered laser-induced ultrasound in time domain which contains signal source, scattering and received field is developed under the assumption of singe- scattering. Theoretical results indicate that transversal and longitudinal wave have the commBased on the diffuse wave transfer theory, a theoretical model of singly-scattered laser-induced ultrasound in time domain which contains signal source, scattering and received field is developed under the assumption of singe- scattering. Theoretical results indicate that transversal and longitudinal wave have the common scattering mechanism and the singly-scattered intensity distribution of transversal and longitudinal wave in time regime are got. Furthermore, statistical average depth and attenuation coefficient are discussed for their influence on intensity distribution. The model has given theoretical description for non-destructive evaluation and micro-structural analysis of materials..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 303003 (2012)
Research on Tensile Properties of Inconel 718 Superalloy Fabricated by Laser Rapid Forming Process
Xi Mingzhe, and Gao Shiyou
The tensile mechanical properties in three mutually perpendicular directions of Inconel 718 superalloy sample fabricated by laser rapid forming (LRF) are studied. The influences of heat treatment on both the solidification microstructures of and the tensile mechanical properties in three mutually perpendicular directioThe tensile mechanical properties in three mutually perpendicular directions of Inconel 718 superalloy sample fabricated by laser rapid forming (LRF) are studied. The influences of heat treatment on both the solidification microstructures of and the tensile mechanical properties in three mutually perpendicular directions of Inconel 718 superalloy sample are investigated. It is shown that the tensile mechanical properties of all test specimens are clearly inferior to that of wrought Inconel 718 superalloy. After being heat treated, the coarse columnar dendrites growing epitaxially along the deposition direction of as-deposited Inconel 718 superalloy change to the coarse and non-uniform equiaxed grains due to recrystallization. With the dissolution of Laves phase and precipitation of a large number of strengthening phase γ″ and γ′, the tensile mechanical properties in three mutually directions increase substantially. The tensile properties of tested specimens whose tensile directions are parallel with the base plate reach the tensile properties standard of wrought Inconel 718 superalloy. There are also tested specimens whose tensile mechanical properties in the direction perpendicular to the base plate not meeting the tensile properties standard of wrought Inconel 718 superalloy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 303004 (2012)
Effect of Nozzle Size on the Surface Heat Transfer Dynamics during Cryogen Spray Cooling in Dermatologic Laser Surgery
Zhou Zhifu, Wang Rui, Wang Guoxiang, Guo Liejin, Chen Bin, and Wang Yueshe
Cryogen spray cooling (CSC) in conjunction with laser therapy has been the clinical standard for hypervascular lesions. In order to optimize nozzle and enhance the cooling efficiency to improve the treatment of laser surgery, an experimental system of transient cryogen spray cooling is built and eight straight-tube nozCryogen spray cooling (CSC) in conjunction with laser therapy has been the clinical standard for hypervascular lesions. In order to optimize nozzle and enhance the cooling efficiency to improve the treatment of laser surgery, an experimental system of transient cryogen spray cooling is built and eight straight-tube nozzles with different diameter and length are designed. A thin film thermocouple is directly deposited on the cooling surface to measure the surface temperature during the cryogen spray cooling. An analytical expression based on Fourier′s law and Duhamel′s theorem is used to calculate surface heat flux from the temperature measurements. Based on the measurements and calculations, the effect of the eight straight-tube nozzles on the heat transfer dynamics of the cooling surface and the atomization characterics are comparatively studied. Additionally, the criterion to evaluate the cooling efficiency of different nozzles is proposed, and the variation of heat extraction from the cooling surface with different spray distances by different nozzles is given..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 303005 (2012)
Research on Carbonized Layer for Truing and Dressing of Bronze-Bonded Diamond Grinding Wheels with Laser
Chen Genyu, Chen Chong, Bu Chun, Jia Tianyang, and Yu Chunrong
For the truing and dressing bronze-bonded diamond grinding wheel by acoustic-optic Q-switched YAG pulsed laser, a three-dimensional (3D) mathematical simulation model and a heat transfer model of single pulsed laser ablating the diamond abrasive are established by ANSYS finite element software. The models show the tempFor the truing and dressing bronze-bonded diamond grinding wheel by acoustic-optic Q-switched YAG pulsed laser, a three-dimensional (3D) mathematical simulation model and a heat transfer model of single pulsed laser ablating the diamond abrasive are established by ANSYS finite element software. The models show the temperature distribution of diamond under different laser parameters, and they are proved to be correct through experiments. According to the two different procedures of dressing and shaping of bronze-bonded diamond grinding wheels, from both experiment and numerical simulation much research work is done on the relationship of pulsed laser parameters and the depth of carbonized layer. The results show that there is not much difference between the influences of pulse width and laser power on the depth of carbonized layer in dressing, but pulse width plays a dominant role on the depth of carbonized layer in shaping; and the depth of carbonized layer will decrease after multi-pulse ablation; only in dressing will the depth of carbonized layer decrease with the increase of pulse width..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 303006 (2012)
Subsurface Damage Characterization of Ground Fused Silica by HF Etching Combined with Polishing Layer by Layer
Yang Minghong, Zhao Yuan′an, Yi Kui, and Shao Jianda
Subsurface damage would be inevitably formed during grinding of brittle material. The characterization and removal of the subsurface damage remains the main concern to acquire the high laser-induced damage threshold fused silica optics. Several subsurface damage characterization techniques are revieved, in which the feSubsurface damage would be inevitably formed during grinding of brittle material. The characterization and removal of the subsurface damage remains the main concern to acquire the high laser-induced damage threshold fused silica optics. Several subsurface damage characterization techniques are revieved, in which the feasibility of etching and surface peak-to-valley (PV) roughness method is revaluated experimentally and the error is also analyzed. Herein a new subsurface damage characterization using HF etching and polishing layer by layer is proposed. Then, these subsurface damage characterization techniques are compared in applying to ground fused silica samples. And a good concordance between different measurements is found..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 303007 (2012)
Numerical Simulation of Laser-Generated Lamb Waves in Anisotropic Plates
Xu Baiqiang, Chen Lijuan, Xu Guidong, Xu Chenguang, and Luo Ying
Numerical model for laser-generated Lamb waves is established based on spectral finite element method and modal expansion method. The dispersion curves and propagation characteristics of laser-generated Lamb wave propagating along different directions are simulated. The simulation results show that phase velocity and gNumerical model for laser-generated Lamb waves is established based on spectral finite element method and modal expansion method. The dispersion curves and propagation characteristics of laser-generated Lamb wave propagating along different directions are simulated. The simulation results show that phase velocity and group velocity of guided waves in anisotropic plates can be calculated efficiently by using spectral finite element method. And the laser-generated Lamb wave can be simulated in any direction by combining spectral finite element method with the modal expansion method. Furthermore, propagation velocity and dispersion characteristics of Lamb waves in different directions are closely related to the anisotropy of the material. The numerical simulation provides a theoretical basis for better understanding of the propagation of guided wave, the choice of excited signal and the identification of detected signal in the complex media..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 303008 (2012)
Steel-to-Aluminum Fiber Laser Butt Welding with Si Powder Pre-Filling
Wang Tao, Zhou Dianwu, Peng Yan, Zhang Yi, and Chen Genyu
Technical problems like difficulty of fusion and brittle intermetallic compounds between Fe and Al are urgently to be solved in order to get high quality steel-to-aluminun weld seam with high efficiency. Low-carbon steel and aluminun alloy sheet (thicknesses are 5 mm and 6 mm, respectively) are welded in butt way by a Technical problems like difficulty of fusion and brittle intermetallic compounds between Fe and Al are urgently to be solved in order to get high quality steel-to-aluminun weld seam with high efficiency. Low-carbon steel and aluminun alloy sheet (thicknesses are 5 mm and 6 mm, respectively) are welded in butt way by a fiber laser. Welding conducted with Si powder as the filler placed in the end before welding is also researched. Good welding beads have been obtained through adjusting the process parameters and pre-filling Si powder. The welding bead is detected and observed by metallurgical microscope, scanning electron microscope, X-ray diffraction and some other ways. The results indicate that dissimilar steel and aluminun can be connected by laser welding under heat conduction welding mode under the conditions that laser power is 1.8~2.0 kW, welding speed is 8~10 mm/s, defocusing is -2 mm, protective gas is Ar, gas flow rate is 15 L/min and offset to crevice between steel and aluminun is 0.2 mm. The grains in weld zone are fine. Micro-hardness in weld zone is higher than those in heat affected zone and base material. The boundary between steel and aluminum is clear. Two base materials are combined by the molten metal, embedded in each other like gears. The quantities of the melting metals Fe and Al in the pool are controlled. The fluidity of the pool is improved by the Si powder filler and it is good for melting metal to spread out in the end of the sheets. Compounds of Al9Si and Fe0.9Si0.1 with better stability are found and the generation of intermetallic compounds of Fe-Al is inhibited..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 303009 (2012)
Experimental Research of Laser Shock Processing 6061-T651 Aluminum Alloy during Elevated Temperature
Ren Xudong, Ruan Liang, Huangfu Yongzhuo, Zhan Qiubo, Yang Huimin, and Zhang Yongkang
The 6061-T651 aluminum alloy samples are treated by laser shock processing (LSP) with high power and short pulse NdYAG laser, and then are kept warm at 200 ℃, 300 ℃, 400 ℃ and 500 ℃ respectively. The effects of 6061-T651 aluminum alloy on mechanical properties after LSP are analyzed from residual stress, micro-hardnessThe 6061-T651 aluminum alloy samples are treated by laser shock processing (LSP) with high power and short pulse NdYAG laser, and then are kept warm at 200 ℃, 300 ℃, 400 ℃ and 500 ℃ respectively. The effects of 6061-T651 aluminum alloy on mechanical properties after LSP are analyzed from residual stress, micro-hardness and microstructure during elevated temperature. The results indicate that the strengthening effect of 6061-T651 aluminum alloy by LSP at elevated temperature is obvious. The maximum residual stress of specimens are tested in subsurface at 200 ℃ and 400 ℃. At the same time, the higher the temperature, the faster the residual stress releases. The hardening layer depth of 6061-T651 aluminum alloy is about 0.3 mm. The primary cause of improving micro-hardness is grain size and strengthening phase, and the pitting resistance of 6061-T651 aluminum alloy is improved obviously by the big and discontinuous precipitated phase..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 303010 (2012)
Laser Physics
Research on Control Technique for Pound-Drever-Hall Laser Frequency Stabilizing System
Bian Zhenglan, Huang Chongde, Gao Min, Dong Zuoren, Liu Jiqiao, Cai Haiwen, and Qu Ronghui
A laser frequency stabilizing system for Doppler lidar wind measurement is developed, which has the advantages of compact structure and flexible operation. The radio frequency modulating signal is generated by the direct digital frequency synthesizer (DDS), the laser frequency drifts are demodulated by the analog mixerA laser frequency stabilizing system for Doppler lidar wind measurement is developed, which has the advantages of compact structure and flexible operation. The radio frequency modulating signal is generated by the direct digital frequency synthesizer (DDS), the laser frequency drifts are demodulated by the analog mixer, and the functions of the bus controlling, signal processing and proportional-integral differential (PID) servo controlling are implemented by the high integrate chip of digital signal processor (DSP) as the heart of the frequency stabilizing system. The measured laser frequency drifts are less than ±17 kHz during 2.5 h, and whose root mean square (RMS) error is 5 kHz, and absolute frequency stability is better than 200 kHz. The anti-interference performance is also measured. The system will take 30 ms to get back into stabilization when a regular disturbance with the frequency of 6 Hz is put on the Fabry-Perot interferometer (FPI). The system can be applied to Doppler lidar wind measurement..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 302001 (2012)
Polarization Properties of High-Power Vertical-Cavity Bottom-Emitting Lasers
Wang Wei, Ning Yongqiang, Zhang Jinlong, Qin Li, Liu Yun, and Wang Lijun
When using vertical-cavity surface-emitting lasers (VCSEL) as laser source, in order to obtain high-power polarized laser, polarization feature 980 nm large-aperture bottom-emitting VCSEL is investigated in this paper. A rectangular-shaped VCSEL is fabricated by etching rectangular mesa structure and rectangular outputWhen using vertical-cavity surface-emitting lasers (VCSEL) as laser source, in order to obtain high-power polarized laser, polarization feature 980 nm large-aperture bottom-emitting VCSEL is investigated in this paper. A rectangular-shaped VCSEL is fabricated by etching rectangular mesa structure and rectangular output aperture. The maximum power of bottom-emitting rectangular-shaped VCSEL is 660 mW with 550 μm×300 μm output aperture under continuous wave condition, and the differential resistance is 0.09 Ω. It is found that H-polarization (horizontal) and V-polarization (vertical) demonstrated steadily coexistence over the entire range of operation current. And H-polarization dominated over V-polarization which is parallel to the shorter side of the rectangular output aperture. Compared with the circular-shaped VCSEL, both H-polarization and V-polarization nearly have the same lasing situation. Spectrum blue-shift of H-polarization light occurres with respect to V-polarization light. This phenomenon is explained by the symmetric three layer waveguide model. The dependence of the orthogonal polarization ratio on the aspect ratio of the output aperture is investigated in the rectangular-shaped VCSEL. It is found that the rectangular post is an effective way to stabilize the output polarization of large-aperture VCSEL, which can emit high-power polarized laser..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 302002 (2012)
Three-Dimensional Simulation Analysis and Design by Ray-Tracing Method for Microcylinders and Two Kinds of Lens Duct
Han Kezhen, Liu Xiaojuan, Ge Xiaolu, Geng Xue, Wan Yunfang, Fu Shenggui, and He Jingliang
The coupling system consisting of microcylinders and lens duct is an important part of high power all-solid-state lasers. Its coupling performance has direct influence on the laser′s output power and beam quality. The rays distribution inside the system and on the lasering crystal surface should be studied to optimize The coupling system consisting of microcylinders and lens duct is an important part of high power all-solid-state lasers. Its coupling performance has direct influence on the laser′s output power and beam quality. The rays distribution inside the system and on the lasering crystal surface should be studied to optimize the coupling system′s structural parameters. Utilizing a 3D ray-tracing method, the real spatial lights propagating through mocrocylinders and lens duct are traced and the energy transfer efficiency and light distribution are calculated. The coupling characteristics of a hexahedral lens duct and a tapered lens duct are compared. The results show that the hexahedral lens duct needs a bigger length and can achieve higher energy coupling efficiency, while the tapered lens duct can get the light distribution closer to round and the length can be very short..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 302003 (2012)
A Transcendental Laser Intensity Function and Its Numerical Fitting Method
Yuan Wenquan, and Gong Yan
A transcendental function is proposed to describe laser intensity distribution, and its fitting method is given. The transcendental function which is based on Gaussian distribution function is fitted by multivariable optimization method, concretely by direction search method combined with least square method. The resulA transcendental function is proposed to describe laser intensity distribution, and its fitting method is given. The transcendental function which is based on Gaussian distribution function is fitted by multivariable optimization method, concretely by direction search method combined with least square method. The results show that the transcendental function is more suitable than Gaussian distribution function to describe laser intensity distribution; and the time complexity of direction search method [O(∑4i=1Ni)] is much smaller than that of traditional enumeration method [O(∏4i=1Ni)]..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 302004 (2012)
Second Harmonic Generation Characteristics of Continuous Wave Narrow-Linespectrum All Fiber Amplifier in PPSLT
Jiao Mengli, Lü Xinjie, Liu Chi, Yuan Ye, Qi Yunfeng, Ding Yaqian, Zhao Gang, and Zhou Jun
The combination of 1 μm continuous wave (CW), high power, narrow-linespectrum fiber amplifier and the periodically poled materials with high second harmonic generation efficiency provides a compact and high efficiency approach for wavelength conversion with high beam quality. A polarization maintaining all fiber amplifThe combination of 1 μm continuous wave (CW), high power, narrow-linespectrum fiber amplifier and the periodically poled materials with high second harmonic generation efficiency provides a compact and high efficiency approach for wavelength conversion with high beam quality. A polarization maintaining all fiber amplifier with the master-oscillator power amplifier (MOPA) is built. 30 W CW fiber laser is obtained with 0.035 nm linewidth at 1064.25 nm center wavelength. Single-pass, second-harmonic generation of the fiber laser in periodically poled stoichiometric lithium tantalate (PPSLT) made in China is demonstrated. Stabilizing the temperature at 145.6 ℃, 2.1 W green light is achieved at the pump fundamental power of 21.5 W. The effects on the second harmonic generation efficiency produced by temperature, input power density, and Boyd-Kleinman focusing parameter are analysed. Higher power green light can be expected by increasing the fundamental power because the saturation effect is not observed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 302005 (2012)
Research on Transform Lens in Spectral Beam Combination for Laser Diode Array
Hao Mingming, Zhu Hongbo, Qin Li, Wang Lijun, and Liu Yun
Plane-convex lens or bi-convex lens are commonly used as transform lens while the beam of laser diode array (LDA) is spectrally combined by grating-external cavity method. However, the feedback efficiency of external cavity is rather low for each emitter. For example, feedback efficiency for on-axis emitter is just 80.Plane-convex lens or bi-convex lens are commonly used as transform lens while the beam of laser diode array (LDA) is spectrally combined by grating-external cavity method. However, the feedback efficiency of external cavity is rather low for each emitter. For example, feedback efficiency for on-axis emitter is just 80.5% and even decreases to 49.7% for edge emitter. In order to solve the problem, a method that discretely doublet lenses are applied as transform lenses to enhance the feedback efficiency. An equivalent optical setup of traditional spectrally beam combination for LDA is drawn and studied by Zemax optical software. At the same time, feedback efficiency of each emitter will be computed. The imaging characteristic of plane-convex lens is learned by aberration theory and the fact that spherical aberration and coma of plane-convex lens are relative large, which will decrease the feedback efficiency. Funthermore according to primary aberration theory, a discretely doublet is designed by PW method and the doublet is also optimized by Zemax. The feedback efficiency of each LDA emitter whose width is 10 mm is more than 94.2% by using optimized doublet, which is dramatically larger than that of plane-convex lens.The results show that the method is helpful for increasing the coupling efficiency of LDA..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 302006 (2012)
Transmission Characteristics of Optical Field in 2D Random Medium of Non-Spherical Particles
Li Zhiquan, Zheng Sha, Niu Liyong, Li Wenchao, and Sun Yuchao
Transmission characteristics of optical field in 2D random medium of non-spherical particles are studied. Based on the overall scattering effect, a two-dimensional random media model of non-spherical particles as scattering particle is established. The Maxwell equations for the model are built. Using non-uniform mesh fTransmission characteristics of optical field in 2D random medium of non-spherical particles are studied. Based on the overall scattering effect, a two-dimensional random media model of non-spherical particles as scattering particle is established. The Maxwell equations for the model are built. Using non-uniform mesh finite different time domain (FDTD) method to solve Maxwell′s equations, the transmission and spatial distribution of TM mode in the two-dimensional random medium model of non-spherical particles has been achieved. Using the data obtained from simulation, light emission spectrum in frequency domain is calculated by fast Fourier transform (FFT). Compared with previous studies, the results show that in the non-spherical particle systems, the light intensity is different from the intensity in spherical particle systems which increases with the concentration of scattering particles increasing, and it is of oscillation. The emission spectrum shows mode competitions in non-spherical particles systems are stronger than the spherical particle systems. They are easier to realize mode selection..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 302007 (2012)
Modeling and Experimental Study at Thermal Effect of High Power Bounce-Pumped Slab Amplifiers
Li Huanhuan, Li Shiguang, Ma Xiuhua, Wang Juntao, and Zhu Xiaolei
The theoretical simulation and experimental study on thermal effect of bounce-pumped slab amplifier is presented. Based on an efficient cooling of conductively cooled, the temperature distribution of the slab is calculated by finite element analysis, and the beam quality is calculated by the method of moments, which giThe theoretical simulation and experimental study on thermal effect of bounce-pumped slab amplifier is presented. Based on an efficient cooling of conductively cooled, the temperature distribution of the slab is calculated by finite element analysis, and the beam quality is calculated by the method of moments, which gives a guide for the thermal compensation. The focal length is obtained experimentally and the experimental results agree with the theoretical analysis well. When the three-stage amplifier is operated at the repetition frequency of 250 Hz, with a designed thermal compensation lens, an output laser whose pulse energy is 537 mJ and the beam quality factor M2x=2.35, M2y=2.66, is obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 302008 (2012)
Theoretical Study About Real-Time Manipulation of Optical Cage with Double-Ring-Shaped Hybridly Polarized Vector Beam
Liu Haigang, Yang Yanfang, He Ying, Leng Mei, Chang Qiang, and Li Chunfang
A new theoretical method of realizing real-time manipulation of the optical cage by changing the hybrid polarization states of a double-ring-shaped hybridly polarized vector beam is proposed. The hybrid polarization states can be formed by a double-ring-shaped radially polarized beam through a wave plate. The intensityA new theoretical method of realizing real-time manipulation of the optical cage by changing the hybrid polarization states of a double-ring-shaped hybridly polarized vector beam is proposed. The hybrid polarization states can be formed by a double-ring-shaped radially polarized beam through a wave plate. The intensity distribution of the focused double-ring-shaped hybridly polarized vector beams is numerically simulated in the vicinity of the focal plane by using Richards-Wolf vectorial diffraction method. The results show that the optical cage can be formed when the phase delay angle is zero, and the optical cage can be real-time manipulated when the phase delay angle is not zero. The polarization state can be changed by adjusting the phase delay angle of the liquid crystal variable retarder, which can be continuously varied from 0 to π. The realization and manipulation of the optical cage in real time aroused by the phase delay angle will have great potential applications in the field of micro-manipulation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 302009 (2012)
Measurement and Metrology
Study of Calibrating Algorithm for Wavefront Reference Source of Point Diffraction Interferometer
Zhang Yu, Jin Chunshui, Ma Dongmei, and Wang Liping
In order to improve the measuring accuracy of double fibers point diffraction interferometer, system errors of two wavefront reference sources (WRS) should be calibrated. A calibrating process and calibrating algorithm of WRS are designed. The non-axisymmetric errors of WRS about optical axis are obtained through rotatIn order to improve the measuring accuracy of double fibers point diffraction interferometer, system errors of two wavefront reference sources (WRS) should be calibrated. A calibrating process and calibrating algorithm of WRS are designed. The non-axisymmetric errors of WRS about optical axis are obtained through rotating the tested optical system around optical axis by four times. The non-axisymmetric errors of WRS about oblique axis are obtained through rotating the tested optical system around oblique axis by four times. Then the axisymmetric errors of WRS are gotten by the least squares, and the system errors of WRS are equal to the sum of the axisymmetric errors and non-axisymmetric errors. The process of calibrating algorithm is simulated by computer. When the rotating tolerances of WRS are in the range of ±1°, the root mean square value of measuring error is less than 0.01 nm using the 36 terms of Zernike polynomials, which is in the range of calibrating accuracy. The validity of calibrating algorithm is verified and the rotating tolerances of WRS are given by simulating the calibration..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 308001 (2012)
An Concentric Circles and Wedge Grating-Based Camera Self-Calibration Method
Xue Junpeng, Su Xianyu, and Dou Yunfu
A new method for camera calibration by using concentric circles and wedge grating based on the orthogonal vanishing point calibration is proposed. This method uses the characteristics of the high-precision of the phase extraction to obtain the feature points, thus avoiding the calibration errors caused by the traditionA new method for camera calibration by using concentric circles and wedge grating based on the orthogonal vanishing point calibration is proposed. This method uses the characteristics of the high-precision of the phase extraction to obtain the feature points, thus avoiding the calibration errors caused by the traditional marker extraction errors. The camera should capture the pattern images at least six positions. The wrapped phase of the grating can be gained by four-step phase shifting and the zero phase intersection points coordinate of the wrapped phase are calculated from images. The vanishing points and all the intrinsic parameters of the camera can be calculated. According to the simulation experiment analysis results which include factors influencing the vanishing point calibration accuracy, the concentric circles grating with seven periods and the wedge grating with four periods are designed. In the real measuring experiment, the grating target and gray concentric circles target are used to calibrate the camera respectively. Through comparing the reprojective errors of the two methods, it can be proved that the method proposed improves the calibration accuracy and robustness for the vanishing point calibration algorithm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 308002 (2012)
Maximum-Likelihood Estimation of Laser Pointing Errors Using Return Photons
Zhou Lei, Ren Ge, Tan Yi, and Li Zhijun
Boresight and jitter are two fundamental pointing errors for a laser pointing system. With the theory of maximum-likelihood estimation, a laser pointing system model is setup and consummated based on a Gaussian far-field irradiance profile and a Gaussian beam jitter model. The estimates are gained by use of return photBoresight and jitter are two fundamental pointing errors for a laser pointing system. With the theory of maximum-likelihood estimation, a laser pointing system model is setup and consummated based on a Gaussian far-field irradiance profile and a Gaussian beam jitter model. The estimates are gained by use of return photon counts reflected from an intended target. Then, a Monte Carlo simulation is programmed and a laboratory experiment is performed. Both the simulations and experimental results demonstrate that the performance of the maximum-likelihood estimator is excellent and improves with the increasing number of shots. With this method, the boresight and jitter can be obtained simultaneously. What′s more, the further study finds that the experimental results agree well with the simulation results. Based on these excellent performances of the estimator, a closed-loop laser pointing experiment is exhibited in laboratory..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 308003 (2012)
A Novel Method for 2D Phase Unwrapping Guided by Quality Cut
Wu Yonghui, Cheng Xiaosheng, Cui Haihua, and Dai Ning
A novel phase unwrapping method guided by a new kind of branch cut called "quality cut" is proposed after analysis of the many existing path-following methods. The quality cut is defined by means of double thresholds and non-maximum suppression with predefined phase quality factor and phase orientation factorA novel phase unwrapping method guided by a new kind of branch cut called "quality cut" is proposed after analysis of the many existing path-following methods. The quality cut is defined by means of double thresholds and non-maximum suppression with predefined phase quality factor and phase orientation factor. Then the quality at is balanced through expansion, and the phase unwrapping procedure is conducted by the guidance of the quality cut. The perfect location of the quality cut makes the unwrapped phase more reliable and more accurate. Experiments demonstrate the comprehensive result with high accuracy, fast speed and great stability, indicating the practical applicability of the proposed method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 308004 (2012)
Measurement and Experimental Study of Laser Reflectance Characteristics of Camouflage Coat
Ling Jun, Zhang Shuanqin, Wu Jianye, and Pan Jialiang
By means of analyzing concealment mechanism of camouflage coat versus laser semi-active guidance, the laser camouflage technology approach of reducing coat laser reflectivity and controlling surficial laser spatial reflectance characteristics simultaneously is put forward. According to the actual demand of laser reflecBy means of analyzing concealment mechanism of camouflage coat versus laser semi-active guidance, the laser camouflage technology approach of reducing coat laser reflectivity and controlling surficial laser spatial reflectance characteristics simultaneously is put forward. According to the actual demand of laser reflectance characteristics measurement in the process of researching camouflage coat, the measurement theory, method, characteristics of hemisphere reflectivity and bidirectional reflectance factor are analyzed, and laser reflectance characteristics of camouflage coat are studied experimentally with the measuring devices that have been developed. Experimental results show that the proposed methods can accurately and objectively measure laser reflectance characteristics of camouflage coat, and guide laser absorbefacient compound design and surface technical control of coat..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 308005 (2012)
Micro and Nano Optics
Numerical Analysis of Multi-Layer Optical Microsphere Cavity Coupled with a Waveguide
Hao Peng, Dong Yongchao, Cao Zhaolou, Wang Keyi, Wu Qinglin, and Wu Shuo
The finite difference time domain (FDTD) method is employed to simulate the homogeneous, two-layer and three-layer microcavities. Via comparing their respective energy density distributions, it is found that the three-layer microcavity has the highest maximum energy density (Imax), stored energy (En) and the smallest mThe finite difference time domain (FDTD) method is employed to simulate the homogeneous, two-layer and three-layer microcavities. Via comparing their respective energy density distributions, it is found that the three-layer microcavity has the highest maximum energy density (Imax), stored energy (En) and the smallest mode volume (Veff). An optimal gap exists between the multi-layer microcavity and the waveguide, which is 60~120 nm in the paer. A microcavity which has a higher Imax(higher than 360) or a smaller Veff (smaller than 0.03) with particular wavelength can be got by varying the middle layer′s thickness or refractive index. The microcavity with an output waveguide is analyzed with the Gaussian beam excitation. The frequency spectrum in the output waveguide is similar to that in the mircocavity. The multi-layer microsphere cavity can achieve frequency-selecting and light-export. These studies and results show that multi-layer microsphere cavity has better performance and provide new optimizing methods for the design and practical application of microsphere cavity..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 310001 (2012)
Optical Communication
Coated and Tapered Fiber Transmission Characteristics Based on Temperature Variation
Fu Haiwei, Xu Shichao, Qiao Xueguang, Liu Yinggang, Zhou Hong, Luo Mingshi, and Qiu Shuwei
Based on the basic principles of tapered optic fiber transmission, this paper primarily analyzes the transmission characteristics of fused tapered optic fiber which is coated with refractive index-matching fluid versus the index-matching liquids′ temperature variations. The transmission loss curves of computer simulatiBased on the basic principles of tapered optic fiber transmission, this paper primarily analyzes the transmission characteristics of fused tapered optic fiber which is coated with refractive index-matching fluid versus the index-matching liquids′ temperature variations. The transmission loss curves of computer simulation and experiment are very close in tendency. The results show the relationship between the transmission characteristics of tapered optic fiber and the temperature changes. With the temperature increment of outside ambient, the refractive index of index-matching liquids declines. Based on this, the ratio of the optical power carried by the tapered fiber to the total optical power increases. As a result, transmission loss is reduced. Based on the transmission characteristics of this optical device, a temperature-controlled short-pass filter is proposed, the cut-off wavelength of this filter becomes longer with the temperature increased. The rejection efficiency can be above 35 dB and the temperature coefficient of this filter is 40 nm/℃..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 305001 (2012)
Simultaneous Measurement of Temperature and Strain Based on a Long-Period Fiber Grating Combined with a Lyot Fiber Filter in a Linear Configuration
Tong Zhengrong, Guo Yang, Yang Xiufeng, and Cao Ye
A novel sensor for simultaneous temperature and strain measurement based on fiber interference is proposed. The sensor is formed by incorporating a long-period fiber grating (LPFG) inside a Lyot fiber filter (LFF), in which the LFF can be constructed by placing a polarization maintaining fiber (PMF) between two polarizA novel sensor for simultaneous temperature and strain measurement based on fiber interference is proposed. The sensor is formed by incorporating a long-period fiber grating (LPFG) inside a Lyot fiber filter (LFF), in which the LFF can be constructed by placing a polarization maintaining fiber (PMF) between two polarizers (PL) with the primary axis of the fiber rotated 45° relative to the polarizer axes. Due to the different responses of the LFF and LPFG to temperature and strain variations, it is possible for the proposed fiber sensor to measure temperature and strain simultaneously by use of a well-conditioned sensitivity matrix equation. The experimental temperature sensitivity coefficients of LFF and LPFG are -1.3173 nm/℃ and 0.0604 nm/℃, respectively. The strain sensitivity coefficients achieve -0.0185 nm/με and -0.0004 nm/με, respectively. A sensing resolution of ±1 ℃ in temperature and ±25 με in strain has been experimentally obtained. The experimental results are in good agreement with the theoretical analysis. Furthermore, this linear configuration is simple and easy to achieve, and has high stability and sensitivity..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 305002 (2012)
Effect of Lateral Force on Reflected Polarization Dependent Loss Property of Low-Birefringence Fiber Bragg Gratings
Wang Qiyu, Li Qianghua, Guo Bingxia, and Tian Chunhua
According to coupled mode theory, the reflected polarization dependent loss (RPDL) property of fiber Bragg grating (FBG) under lateral force has been studied deeply. The numerical simulation of the RPDL under different lateral force is developed, and the simulation results show that the response of RPDL is very sensitiAccording to coupled mode theory, the reflected polarization dependent loss (RPDL) property of fiber Bragg grating (FBG) under lateral force has been studied deeply. The numerical simulation of the RPDL under different lateral force is developed, and the simulation results show that the response of RPDL is very sensitive to lateral force. Peak height and peak position change greatly with force. Conducting a large number of experiments, experimental results accord with theoretical analysis; moreover, the results show the changing curves of RPDL peak height and peak position within a certain range are in good linear relationship. Therefore RPDL can achieve the sensitive monitoring to the changes of force field information, and a new method for FBG to demodulate exactly is provided..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 305003 (2012)
Study of FBG Strain Distribution Reconstruction Based on Improved Genetic Algorithm Dual Constraint
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Optical fiber Bragg grating (FBG) has been widely used to detect strain. Nevertheless, uneven strain is easy to cause deformation of FBG spectrum, which will result in the invalidation of wavelength detection. Therefore, it is necessary to reconstruct the strain along FBG. In response to that traditional strain distribOptical fiber Bragg grating (FBG) has been widely used to detect strain. Nevertheless, uneven strain is easy to cause deformation of FBG spectrum, which will result in the invalidation of wavelength detection. Therefore, it is necessary to reconstruct the strain along FBG. In response to that traditional strain distribution reconstruction theory both have poor effect and slow convergence speed, strain distribution reconstruction theory based on FBG central wavelength and reflectivity of spectrum dual constraint is presented after deep research on improved genetic algorithm, which significantly improves the non uniqueness and the confidence of reconstruction. At the same time, assuming distribution of strain is polynomial, reconstruction of strain distribution is realized through reconstructing the coefficients of the polynomial, which has improved the speed of strain distribution reconstruction. And then strain parameters reconstruction numerical simulation experiments are comprehensively carried out, and the errors of the reconstructing polynomial coefficients are all less than 1.5%. Through tuning FBG by two ends fixed compression bar experiment, the validity, applicability and practicability of the novel reconstructing method have been verified. Consequently, a novel method of reconstructing strain distribution which is fast and efficient has been generated..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 305004 (2012)
Research of High Sensitivity and Anti-Acceleration of DFB Active Fiber Grating Hydrophone
Li Dongming, Chen Jun, Ge Huiliang, and Zhang Zili
The active fiber grating hydrophone with high sensitivity and anti-acceleration is investigated. The λ/4 phase-shift Er3+-doped fiber grating is used as a distributed feedback Bragg (DFB) narrow linewidth laser. Casing this active fiber Bragg grating (FBG) element with the elastic slice to enhance sensitivity the high The active fiber grating hydrophone with high sensitivity and anti-acceleration is investigated. The λ/4 phase-shift Er3+-doped fiber grating is used as a distributed feedback Bragg (DFB) narrow linewidth laser. Casing this active fiber Bragg grating (FBG) element with the elastic slice to enhance sensitivity the high sensitivity hydrophone sensor is constructed. Afterward, the ability of the detection to hydrophone motion is enhanced by using the both sides symmetrical elastic slices to encapsnlate the disturber of the axile acceleration. And then, the capability of resisthy resting water pressure is promoted via strustural optimization. In a frequency range of 100~1000 Hz the sound-phase sensitivity reached -132.7±0.7 dB (0 dB=1 rad/μPa). The acceleration sensitivity is under -20 dB (0 dB=1 rad/g). The resisting resting water pressure capability is up-to 2 MPa..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 305005 (2012)
Visibility Analysis of Interferometric Fiber Bragg Grating Defined Fabry-Perot Sensor System under Gaussian Profile Approximation
Niu Siliang, Rao Wei, Liang Xun, and Hu Yongming
Spectral mismatch between spectral profiles of two fiber Bragg gratings (FBGs) can deteriorate the fringe visibility of the constructed fiber Fabry-Perot (FFP) sensor system. Under the approximation of Gaussian profiles to reflection spectra of weak fiber Bragg gratings, the expression describing fringe visibility variSpectral mismatch between spectral profiles of two fiber Bragg gratings (FBGs) can deteriorate the fringe visibility of the constructed fiber Fabry-Perot (FFP) sensor system. Under the approximation of Gaussian profiles to reflection spectra of weak fiber Bragg gratings, the expression describing fringe visibility variations induced by spectral mismatch is deduced. The curve of fringe visibility is measured in an interferometric FFP sensor system, which is in good agreement with the theoretical analysis. The investigation indicates that, side lobes in reflection spectra of FBGs have a big influence upon visibility variations caused by spectral mismatch. And from the spectral match point of view, the FFP sensor system based on Gaussian apodized gratings is superior compared with that on normal uniform gratings..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 305006 (2012)
Design and Implementation of Comb Filter with Arbitrary Channel Spacing Based on Fiber Bragg Gratings
Sun Guodan, Wang Rong, Pu Tao, Wei Zhihu, and Wang Hongbo
For a given chirp phase mask, only comb filter with special channel spacing can be fabricated. A novel approach to implement arbitrary channel-spacing comb filters based on direct current (DC) phase shift in fiber Bragg grating (FBG) is proposed. Arbitrary channel-spacing comb filter can be achieved by a single chirpedFor a given chirp phase mask, only comb filter with special channel spacing can be fabricated. A novel approach to implement arbitrary channel-spacing comb filters based on direct current (DC) phase shift in fiber Bragg grating (FBG) is proposed. Arbitrary channel-spacing comb filter can be achieved by a single chirped phase mask and a submicrometer-precision translation stage. The proposed method is cost-effective, flexible and simple compared to traditional ways. Simulation and experiment show that arbitrary phase shifts introduced by DC refractive index modulation can be achieved. Multichannel comb filter with channel spacing of 100, 50, 40 GHz are implemented with a same phase mask. The impact of DC phase shift length and phase errors on side band suppression ratio are also analyzed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 305007 (2012)
Analysis and Experimental Study of Inner Stress for Metallized Fiber Bragg Gratings
Pi Haoyang, Liu Qiong, Ye Qing, Xin Guofeng, Cai Haiwen, Qu Ronghui, and Fang Zujie
By using chemical metallization, nickel layer is coated on the fiber Bragg grating with different thicknesses. The inner stress occurs due to different thermal expanding coefficients between nickel layer and fiber grating layer, which is influenced by metal-film thickness. In this paper, the relationship between the waBy using chemical metallization, nickel layer is coated on the fiber Bragg grating with different thicknesses. The inner stress occurs due to different thermal expanding coefficients between nickel layer and fiber grating layer, which is influenced by metal-film thickness. In this paper, the relationship between the wavelength shift and the thickness of nickel layer is theoretically analyzed. Moreover, the in-situ observation of the fiber grating during electroless plating and the wavelength shift as a function of metal-film thickness are investigated. A good agreement is found between the experimental and calculated results..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 305008 (2012)
Method of Establishing Channel Model in Multiple-Beam Transmission and Reception FSO Systems
Xu Jianwu, Wang Hongxing, Sun Xiaoming, and Liu Jun
In single-beam transmission and reception free-space optical communication (FSO) systems, the intensity scintillation obeys the negative exponential distribution in weak turbulence while in strong turbulence it obeys logarithm normal distribution, which is universally accepted at present. Because the Gamma-Gamma distriIn single-beam transmission and reception free-space optical communication (FSO) systems, the intensity scintillation obeys the negative exponential distribution in weak turbulence while in strong turbulence it obeys logarithm normal distribution, which is universally accepted at present. Because the Gamma-Gamma distribution can describe both weak turbulence and strong turbulence, it becomes the hot spot recently. By extending them to multiple-beam transmission and reception FSO systems, the intensity scintillation′s probability density distribution functions are deduced and the channel models are established based on these distributions respectively. At last, the analysis of the influences of communication range, laser wavelength, receiving aperture as well as transmission and receiving antenna numbers on the channel model based on the negative exponential distribution and the simulations are detailedly done. All of these benefit theoretical research and design of the multiple-beam transmission and reception FSO systems..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 305009 (2012)
K-Band and High Stability Optoelectronic Oscillator
Sun Bin, Yu Jinlong, Wang Ju, Miao Wang, Meng Tianhui, Wang Wengrui, and Yang Enze
A kind of dual-loop optoelectronic oscillator (OEO) with high stability, high spectral purity and low phase noise is introduced . The principle of OEO is analyzed theoretically. Side-mode suppression is achieved by using dual-loop in optical domain. The length of fiber loop is controlled by detecting the change of outpA kind of dual-loop optoelectronic oscillator (OEO) with high stability, high spectral purity and low phase noise is introduced . The principle of OEO is analyzed theoretically. Side-mode suppression is achieved by using dual-loop in optical domain. The length of fiber loop is controlled by detecting the change of output signal′s frequency. Experiment results of a 20 GHz radio frequency signal with high quality are obtained. It has high spectral purity. Its line width is less than 1 Hz and phase noise is -112 dBc/Hz at 10 kHz. And its frequency stability achieves 10-10 in 4 h..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 305010 (2012)
Rapid Communications
[in Chinese]
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 305009 (2012)
Remote Sensing and Sensor
[in Chinese]
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 310001 (2012)
Terahertz Technology
Polarization Characteristics of One-Dimensional Metallic Wire-Grating Polarizer in Terahertz Frequency Range
Liu Liming, Zhao Guozhong, Zhang Gaohui, Wei Bo, and Zhang Shengbo
Based on the finite differential time domain (FDTD) method, numerical simulation of polarization characteristics of one-dimensional metallic wire-grating polarizer in the frequency range of 0.2~2.6 THz is carried out. The effects of structural parameters of metallic wire-grid polarizer such as metal duty cycle, the widBased on the finite differential time domain (FDTD) method, numerical simulation of polarization characteristics of one-dimensional metallic wire-grating polarizer in the frequency range of 0.2~2.6 THz is carried out. The effects of structural parameters of metallic wire-grid polarizer such as metal duty cycle, the width of slit and the periodicity of wire-grating on the terahertz transmission at two kinds of polarization modes are investigated. With the technique of photolithography and the metal film deposition, a 200-nm-thick gold film is fabricated on a 1-mm-thick high-resistivity silicon substrate. A series of one-dimensional wire-gratings are formed on the silicon substrate. The transmission spectra of the wire-grating polarizer are measured by the terahertz time domain spectroscopy. The numerical simulations based on FDTD method show a good agreement with experimental results. The results show that it is possible to optimize the performance of one-dimensional wire-grating polarizer through reasonable design of structural parameters. This work provides a good reference for the manufacture of terahertz polarizer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 311001 (2012)
Optical Design and Fabrication
Research on Technology of Influence Square Aspheric Optical Element Processing Accuracy
Wu Qingtang, Nie Fengming, Wang Dasen, Shi Guoquan, Wu Huan, Li Shan, and Guo Bo
The reason of making propeller error in grinding square aspheric optical elements is analyzed. Each rigidity index of two fixing methods of abrasion wheel axis is calculated, and then the influence of abrasion wheel axis fixing position on the processing accuracy. The experiment at each position is done. Different abraThe reason of making propeller error in grinding square aspheric optical elements is analyzed. Each rigidity index of two fixing methods of abrasion wheel axis is calculated, and then the influence of abrasion wheel axis fixing position on the processing accuracy. The experiment at each position is done. Different abrasion wheel and different processing parameter are used to do the grinding experiment. Finally, the abrasion wheel axis fixing position and the grinding processing parameter which can satisfy the processing accuracy of square aspheric optical element are obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 316001 (2012)
A Digital-Grating-Based Alignment Technique in Maskless Lithography
Tang Lulu, Hu Song, Xu Feng, Tang Yan, Chen Mingyong, and Zhu Jiangping
A digital-grating-based alignment technique is brought forward and researched for digital micromirror device (DMD) maskless lithography system. Infinitesimal displacement of a silicon chip is amplified and displayed in moiré fringes generated by digital grating and physical grating. A digital-grating-based alignmeA digital-grating-based alignment technique is brought forward and researched for digital micromirror device (DMD) maskless lithography system. Infinitesimal displacement of a silicon chip is amplified and displayed in moiré fringes generated by digital grating and physical grating. A digital-grating-based alignment model is created in DMD-based maskless lithography system. The alignment marks as well as detailed realization program is designed. Numerical simulation and preliminary experimental test is carried out. Compared to the traditional real mask, the grating digital gating characterized with variable frequency, clear image, good periodic structure and zero mask cost will extend the measurement range and reduce the displacement measurement error. This technique can realize deep sub-micron alignment accuracy, and satisfy the requirements of maskless lithography..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 316002 (2012)
Fabrication of Microlens Arrays Based on Spatial Light Modulator
Shen Su, Pu Donglin, Hu Jin, and Chen Linsen
An approach of fabrication of microlens arrays using spatial light modulator based lithography method is proposed. Combined with themal reflow method, digital micro-mirror device is used to pattern microstructure, and microlens arrays with arbitrary structure and topology can be obtained. The patterns on thick photoresAn approach of fabrication of microlens arrays using spatial light modulator based lithography method is proposed. Combined with themal reflow method, digital micro-mirror device is used to pattern microstructure, and microlens arrays with arbitrary structure and topology can be obtained. The patterns on thick photoresist layer are projected by an infinity-corrected optical system. Good surface quality can be realized by thermal reflow method. Compared with classical stereolithography and mask-based exposure lithography method, the proposed method has the advantage of low-cost and high efficiency, especially suitable for fabricating microlens arrays which feature size ranging from several micrometers to hundreds of micrometers. The obtained microlens array can be transferred to a nickel mold by quasi-lithography electrodeposition and modeling (LIGA) process, which can be used as an imprinting mold. The flexible microlens array film can find wide application in novel ultra-thin liquid crystal displays, organic light-emitting diodes (OLED), etc..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 316003 (2012)
Remote Sensing and Sensors
Surface Plasmon Resonance Sensor Based on Compact Disk Grating
Liu Chang, Zou Zhengfeng, Chen Shufen, Fu Lei, Meng Yanbin, Zhang Bingxin, Chen Bo, and Lin Weixiu
The compact disc (CD) is used as a grating-coupled element in the surface plasmon resonance (SPR) sensor. And the changes in solution concentration are measured by detecting the resonance angle. The results show that the CD grating-coupled SPR sensor′s sensitivity to the glucose solution is low to mass fraction of 3%, The compact disc (CD) is used as a grating-coupled element in the surface plasmon resonance (SPR) sensor. And the changes in solution concentration are measured by detecting the resonance angle. The results show that the CD grating-coupled SPR sensor′s sensitivity to the glucose solution is low to mass fraction of 3%, and the theoretical resolution is mass fraction of 1%. The resonance curves with different grating periods, grating groove forms and refractive indexes of analyte are simulated and the results show that reducing the grating period or using the sinusoidal grating as coupling element can further improve the sensitivity of the sensor..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue 3, 314001 (2012)
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