Journals >Chinese Journal of Lasers
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2010
Volume: 37 Issue 2
52 Article(s)
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Research Article
External Resonator SrWO4 Raman Laser Excited by 1064 nm Pico-Second Pulses
Wang Zhengping, Hu Dawei, Zhang Huaijin, Cheng Xiufeng, Yu Haohai, Xu Xinguang, Sun Xun, Gu Qingtian, Wang Bo, Wang Jiyang, and Shao Zongshu
External resonator stimulated Raman scattering of SrWO4 crystal excited by pico-second pulses is studied. SrWO4 crystal with high optical quality is prepared by Czochralski pulling method. Its size reaches 22 mm×40 mm,and its weight is 72.3 g. The transmission spectrum of SrWO4 crystal is detected by spectrophotoExternal resonator stimulated Raman scattering of SrWO4 crystal excited by pico-second pulses is studied. SrWO4 crystal with high optical quality is prepared by Czochralski pulling method. Its size reaches 22 mm×40 mm,and its weight is 72.3 g. The transmission spectrum of SrWO4 crystal is detected by spectrophotometer,which showes its short-wave limit is 260 nm,and long-wave limit is larger than 3200 nm. It indicates that SrWO4 crystal can realize Raman frequency shifting in a wide wave band. When the exciting source is a 40 ps Nd:YAG mode-locked laser,the total conversion efficiency for multi-wavelengths Raman output reaches 73%,and the largest output energy is 2.58 mJ. The highest conversion efficiency for the first Stocks Raman output of 1180 nm is 38%,and the largest output energy is 1.04 mJ. The conversion efficiency for the second Stocks Raman output of 1324 nm is 19.3%,and the largest output energy is 0.39 mJ. The experimental results show that SrWO4 crystal possesses many advantages such as easy growth,wide transmittion spectrum,large gain coefficient,and high conversion efficiency,which indicate that SrWO4 is a promising solid Raman medium that may have practical applications..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 335 (2010)
Thermal Effect in Nd:GdVO4 Crystal Slab by Laser Diode Double-Side Pumped
Fan Ting, Gao Feng, Shi Peng, Cao Haibin, and Li Jinping
Based on the theory of thermal analysis,heat conduction equation of Nd:GdVO4 crystal slab double-side pumped by laser diode arrays was built. By solving the heat conduction equation,the analytic expression of temperature field and thermal deformation distribution were obtained. As geometry of pumping diodes correspondsBased on the theory of thermal analysis,heat conduction equation of Nd:GdVO4 crystal slab double-side pumped by laser diode arrays was built. By solving the heat conduction equation,the analytic expression of temperature field and thermal deformation distribution were obtained. As geometry of pumping diodes corresponds to 1 mm×1 mm,and the average power is about 10 W,the distribution of one-dimensional temperature field,two-dimensional temperature field and thermal deformation have great difference when four groups of laser diode arrays were in there different locations;contrasting with the temperature distribution and thermal deformation produces by pump source in three positions,the temperature rise and thermal deformation in the location 1 and 2 are relatively small,while those of the location 3 are biggest..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 339 (2010)
Three Methods to Lock the Second Harmonic Generation for 461 nm
Peng Yu, Zhao Yang, Li Ye, Cao Jianping, Fang Zhanjun, and Zang Erjun
This paper shows an external integrated ring cavity used to generate 461 nm blue radiation,which was locked by three different methods,Hansch-Couillaud,Pound-Drever-Hall,and intramodulation. And the factors the length of crystal and waist of fundamental light in crystal that affected the stability of output,were studieThis paper shows an external integrated ring cavity used to generate 461 nm blue radiation,which was locked by three different methods,Hansch-Couillaud,Pound-Drever-Hall,and intramodulation. And the factors the length of crystal and waist of fundamental light in crystal that affected the stability of output,were studied. The experimental results show that the integrated cavity improves the stability of output of 461 nm. And it reaches 3%,including 2% instability of fundamental. Because of absorption of 461 nm,long crystal,small waist and its disposition could impact their power and stability. And the output of second harmonic generation reaches 310 mW,54.8% of the conversion efficiency,and 71.3% of the net conversion efficiency. The reflection ratio of coupling mirror was discussed in addition..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 345 (2010)
Influences of Heat-Dissipation Methods on Thermal Distortion of Laser Rods
Song Xiaolu, Guo Zhen, Li Bingbin, Wang Shiyu, Cai Defang, and Wen Jianguo
In laser diode end-pumped Nd:YAG lasers,temperature distributions in rods under different heat-dissipation methods are calculated by the finite element method. Influences of two heat-dissipation methods,such as copper heat sink conduction method and water flow method on temperature of rods,are compared. Spherical aberrIn laser diode end-pumped Nd:YAG lasers,temperature distributions in rods under different heat-dissipation methods are calculated by the finite element method. Influences of two heat-dissipation methods,such as copper heat sink conduction method and water flow method on temperature of rods,are compared. Spherical aberration of thermal lens is presented. Based on the calculation results and ray-tracing theory,influences of two heat-dissipation methods on focal length of thermal lens distribution are compared quantificationally. Results show that the thermal lens focal length is smaller,focal length differences are shorter and spherical aberration is weaker,when using the heat-dissipation method with copper heat sink and TEC. And the thermal lens focal length is longer but focal length differences are larger and spherical aberration is more obvious,when using the water flow heat-dissipation method,Using the two heat-dissipation methods respectively,thermal lens distortion of a rod is simulated when the heat-dissipation is asymmetric..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 351 (2010)
Angle-Tuned Dual-Signal Quasi-Phase Matching Optical Parametric Generator
Ji Feng, Lu Rongsheng, Li Baosheng, Zhang Baigang, and Yao Jianquan
Angle-tuned dual signal quasi-phase-matched (QPM) optical parametric generator (OPG) based on periodically poled MgO-doped lithium niobate (PPMgLN) pumped by an acousto-optically Q-switched Nd∶YVO4 laser is reported. The PPMgLN crystal is 50 mm long and has a periodical phase reversed grating structure. The grating perAngle-tuned dual signal quasi-phase-matched (QPM) optical parametric generator (OPG) based on periodically poled MgO-doped lithium niobate (PPMgLN) pumped by an acousto-optically Q-switched Nd∶YVO4 laser is reported. The PPMgLN crystal is 50 mm long and has a periodical phase reversed grating structure. The grating period is 29.6 μm and the phase reversed period is 6.808 mm. The crystal is periodically poled along the z-axis by using the external electric poling technique. While the crystal is rotated over the range of 0°-8°,the dual signal wavelengths can be rapidly tuned from 1474.8 to 1479 nm and 1489.5 to 1495.2 nm. The theoretical analysis for angle-tuned dual signal OPG is also presented. The calculated results show good agreement with the experimental data..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 358 (2010)
A Short-Cavity Phosphate Glass Fiber Laser and Its Output Characteristics
Meng Li, Pan Zhengqing, Geng Jianxin, Cai Haiwen, Fang Zujie, Ye Qing, and Qu Ronghui
A 1 cm Er/Yb codoped phosphate glass fiber is used to make a short linear cavity fiber laser to get single-frequency,narrow line width and large power output. Relation of the output power to heat sink temperature is measured. When the heat sink temperature is stabilized at 11 ℃,the slope efficiency is 24%;and its outpuA 1 cm Er/Yb codoped phosphate glass fiber is used to make a short linear cavity fiber laser to get single-frequency,narrow line width and large power output. Relation of the output power to heat sink temperature is measured. When the heat sink temperature is stabilized at 11 ℃,the slope efficiency is 24%;and its output power reaches 79 mW under pump power of 415 mW. The output spectrum shows single longitudinal mode operation at 1534 nm with side mode suppressing ratio (SMSR) above 50 dB. Homodyne measurement gives its line width as narrow as 4.5 kHz. By taking the glass fiber as medium of a low finesse Fabry-Perot (F-P) cavity,refractive index and optic-thermal coefficient of the phosphate glass fiber is measured to be 1.5195 in 1530-1550 nm band and -5.4×10-6℃-1. It is found that the slope efficiency decreases at higher pump power range and the output power increases sub-linearly. This phenomenon and its relation to temperature are discussed qualitatively..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 362 (2010)
Phase Locking of Sixteen Laser Beams Using Stochastic Parallel Gradient Descent Algorithm
Zhou Pu, Wang Xiaolin, Ma Yanxing, Ma Haotong, Xu Xiaojun, and Liu Zejin
Coherent beam combination of up to sixteen fiber laser beams using stochastic parallel gradient descent (SPGD) algorithm is demonstrated. The phase control is implemented by running SPGD algorithm on a digital signal processor (DSP). The combined laser power of the system in close-loop can be improved 12 times comparedCoherent beam combination of up to sixteen fiber laser beams using stochastic parallel gradient descent (SPGD) algorithm is demonstrated. The phase control is implemented by running SPGD algorithm on a digital signal processor (DSP). The combined laser power of the system in close-loop can be improved 12 times compared with the power in open-loop..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 367 (2010)
Design and Experimental Study of an Excimer Laser Based on Solid State Pulsed Power Module
You Libing, Liang Xu, and Yu Yinshan
Thyratron-based excimer lasers are not available for some fields where high pulse repetition rate is desired. A thyratron-free alternative is to introduce solid state pulsed power module (SSPPM) which combines solid-state switch with magnetic switch and promises an infinite lifetime. A SSPPM-based ArF excimer with metaThyratron-based excimer lasers are not available for some fields where high pulse repetition rate is desired. A thyratron-free alternative is to introduce solid state pulsed power module (SSPPM) which combines solid-state switch with magnetic switch and promises an infinite lifetime. A SSPPM-based ArF excimer with metal-ceramic configuration was designed. Corona pre-ionization was employed to achieve a homogeneous and clean pre-ionization. A 10-14 kV pulse was generated by the SSPPM for electrodes discharge. The risetime of the pulse was about 150 ns. Under the pumping density of 7.6 MW/cm3 the maximum laser output energy of 11 mJ was obtained at 193 nm. The maximum repetition rate was up to 300 Hz. This laser may satisfy the applications such as laser vision correction,dermatological treatment and spectroscopy..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 370 (2010)
Excimer Pulse Energy Stabilization Realized by Charging
Liang Xu, You Libing, Wang Tao, and Yu Yinshan
A closed-loop feedback system for excimer laser pulse energy stabilization was introduced,which included a pulse energy detecting part,a switching mode power supply and a controller. Each part of the system was well shielded and the signals between the parts were transmitted by fibers. With average algorithm of pulse-pA closed-loop feedback system for excimer laser pulse energy stabilization was introduced,which included a pulse energy detecting part,a switching mode power supply and a controller. Each part of the system was well shielded and the signals between the parts were transmitted by fibers. With average algorithm of pulse-pulse discharge voltage,the reliable close-loop control can be realized under the condition of strong electromagnetic interference. Tested on a 5 Hz spark discharged KrF laser,the system effectively reduced the laser pulse energy fluctuations standard deviation from 4.71% to 3.01% with a gas fill in a sound situation and from 7.18% to 3.62% with the gas in a poor situation and low discharge voltage. The method can effectively improve the stability of pulse energy..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 374 (2010)
Characteristics of High Power Al-Free Quantum-Well Laser Diode Array
Hu Liming, Li Zaijin, Qin Li, Yang Ye, Wang Ye, Liu Yun, Wang Bingbing, and Wang Lijun
A three dimensional finite element thermal-model is presented for a micro-channel packaged high-power Al-free quantum-well laser diode array(LDA). The influence of working conditions,such as ambient temperature,operating current and duty cycle,on the temperature of the active region is simulated in this paper. And the A three dimensional finite element thermal-model is presented for a micro-channel packaged high-power Al-free quantum-well laser diode array(LDA). The influence of working conditions,such as ambient temperature,operating current and duty cycle,on the temperature of the active region is simulated in this paper. And the variety of the output characteristics of LDA working under different conditions is studied experimentally. It is found that longer time to reach steady-state,higher temperature of the active region,greater red shift of peak wavelength and threshold current,lower conversion efficiency and slope efficiency and lower output power are gained when the laser diode array works at higher ambient temperature and duty cycle. The output characteristics of the laser diode array is extrapolated when it works under the conditions of 20 ℃ ambient temperature,20% duty-cycle and 300 A injecting current. The results show that the output power exceeds 300 W and the conversion efficiency achieves 45% and no thermal rollover appears..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 379 (2010)
Activation Technique of GaN Negative Electron Affinity Photocathode
Du Xiaoqing, Chang Benkang, Qian Yunsheng, Fu Rongguo, Gao Pin, and Qiao Jianliang
Metal organic chemistry vaporation deposition (MOCVD) epitaxial p-type GaN layer is used as emission material of GaN photocathode. By using on-line measurement of photocurrent in activation process,the influences of Cs activation,Cs/O alternate activation and high-low temperature two-step activation techniques on photoMetal organic chemistry vaporation deposition (MOCVD) epitaxial p-type GaN layer is used as emission material of GaN photocathode. By using on-line measurement of photocurrent in activation process,the influences of Cs activation,Cs/O alternate activation and high-low temperature two-step activation techniques on photoemission performance of GaN photocathode are investigated. The experimental results show that GaN photocathode can obtain about 20％ quantum efficiency only by Cs activation,and the quantum efficiency can be increased slightly by two or three Cs/O cycles. But the high-low two-step activation technique can not increase the quantum efficiency. The experimental phenomena are explained by the dipole surface model..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 385 (2010)
Optical Phonon Resonance Characteristics Comparison of KTP and RTP Crystals in Terahertz Time-Domain Spectroscopy
Sang Mei, Qiu Jinhui, Yang Tianxin, Lu Xinchao, and Zhang Weili
By use of photoconductive switches triggered by the ultrafast femtosecond pulses in the terahertz (THz) time-domain spectroscopy (TDS) system,the optical phonon oscillation characteristics of isomorphs KTiOPO4 (KTP) and its crystallographic isomorphs RbTiOPO4 (RTP) crystals are studied in the 0.5-2.0 THz range. AlthougBy use of photoconductive switches triggered by the ultrafast femtosecond pulses in the terahertz (THz) time-domain spectroscopy (TDS) system,the optical phonon oscillation characteristics of isomorphs KTiOPO4 (KTP) and its crystallographic isomorphs RbTiOPO4 (RTP) crystals are studied in the 0.5-2.0 THz range. Although the two crystals have quite similar lattice structure,their terahertz spectrums reveal different characteristics:the absorption of the RTP crystal is stronger than that of the KTP crystal,and the peaks of related optical phonon oscillation of the RTP crystal are more than that of the KTP crystal while the polarization of terahertz field parallels to the z-axis of the crystals. With pseudo-harmonic dielectric model,the complex dielectric constant curves of the two crystals are calculated,and the parameters related to the optical phonon resonances are obtained. The results demonstrate that all these phonon oscillation peaks in terahertz range are corresponding to the optical external modes which are caused by the vibrations of the K (or Rb) ions with the screw of PO4 tetrahedral and TiO6 octahedral. But since the Rb ions have more atomic weight,their chemical band strength with surrounding atoms or groups is correspondingly stronger and complex,which leads to the diversity of optical phonon oscillation modes..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 389 (2010)
Analysis of Characteristic Quantities in High Gain GaAs Photoconductive Semiconductor Switches
Liu Hong, and Ruan Chengli
Several significant characteristic quantities as well as physical mechanism in high gain intrinsic GaAs photoconductive semiconductor switches (PCSS) are analyzed. The model of the streamer on the basis of domain electron avalanche (DEA) is developed. It is presented that the DEA requires three necessary conditions:theSeveral significant characteristic quantities as well as physical mechanism in high gain intrinsic GaAs photoconductive semiconductor switches (PCSS) are analyzed. The model of the streamer on the basis of domain electron avalanche (DEA) is developed. It is presented that the DEA requires three necessary conditions:the lower limit of initial carrier density nLD≥3×1015 cm-3,the local carrier density at least either in the depletion layer or in the accumulation layer of the DEA must exceed the threshold ncs,the characteristic length ΔZ of the activated region along the field must be larger slightly than the width b of the growing domain. The upper limit of the local carrier density created by photo-ionization from the streamer is approximately 1017 cm-3·ps-1,which implies that the carrier density provided for the successive growing domain is approximately 3×1015≤n(t＝0)＜1017 cm-3. Therefore the propagation velocity of streamer is approximately 2.97×108≤vpro≤6.21×109 cm/s. The results of this theoretical analysis are consistent with the reported experimental observations..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 394 (2010)
Distinguishing the Number of Nanometer-Sized Particles in Single Optical Trap by Measuring the Back Scattering of Light
Zhong Mincheng, Zhang Wenjing, Zhou Jinhua, Li Yinmei, Tian Laike, and Bai Jintao
Optical tweezers have increasingly widespread application in a large variety of scientific disciplines because they can trap a micro-particle losslessly. They can also trap multiple particles in single optical trap due to the characteristic of the potential energy of the trap. How to distinguish the number of particlesOptical tweezers have increasingly widespread application in a large variety of scientific disciplines because they can trap a micro-particle losslessly. They can also trap multiple particles in single optical trap due to the characteristic of the potential energy of the trap. How to distinguish the number of particles in single optical trap is the key work in the experiment. A novel method based on laser scattering method to distinguish the numbers of nanometer-particles in single trap was presented in this paper. The number of particles in single trap was distinguished by measuring the intensity of light backscattering with corresponding situation. The number of particles with diameters of 1 μm,0.5 μm,0.2 μm,100 nm,73 nm was distinguished successfully,and the state of optical trap was discussed. This method may find the application of optical tweezers in nanometer dimension..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 398 (2010)
Spectral Characteristics of Multi-Longitudinal-Mode Optically Pumped D2O Submillimeter Wave Laser
Yang Yang, Meng Meng, and Luo Xizhang
Based on the semi-classical density matrix theory,the gain coefficients of infrared (IR) pumping signal and submillimeter wave (SMMW) laser signal for a three-energy-level system in single-longitudinal-mode (SLM) and in multi-longitudinal-mode (MLM) pulse optically pumped D2O SMMW laser are deduced. The spectral characBased on the semi-classical density matrix theory,the gain coefficients of infrared (IR) pumping signal and submillimeter wave (SMMW) laser signal for a three-energy-level system in single-longitudinal-mode (SLM) and in multi-longitudinal-mode (MLM) pulse optically pumped D2O SMMW laser are deduced. The spectral characteristics and output power are calculated by numerical iteration method. The laser processes and the fine structures in spectral characteristics are studied and compared in detail. MLM optically pumped D2O superradiant laser produces a wider SMMW laser line than SLM pumped laser does. In both SLM and MLM optically pumped D2O cavity lasers,SMMW laser lines broaden further and narrow peaks will appear in their spectrum. These narrow peaks correspond to the MLM structure of the SMMW laser line. The wide band spectrum and MLM structure characteristics provide a theoretical basis for frequency tunable SMMW laser..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 404 (2010)
Study and Test on a Novel Fast Laser Scanner Based on Piezo-Actuators
Xiang Sihua, Chen Sihai, Wu Xin, Zheng Xiawei, and Xiao Ding
Laser scanner is one of the most important components in lidar,laser detecting,laser processing,and so on. Existing scanners are difficult to realize fast linear scanning with low moment of inertia. A fast laser scanner based on novel piezoelectric actuators is designed,which has mechanical scanning angle of ±0.35Laser scanner is one of the most important components in lidar,laser detecting,laser processing,and so on. Existing scanners are difficult to realize fast linear scanning with low moment of inertia. A fast laser scanner based on novel piezoelectric actuators is designed,which has mechanical scanning angle of ±0.35° and first resonance frequency of 1872 Hz. Finite element analysis is used to design the scanner structure. Measured frequency response curve shows that the modes of the scanner are complicated. The scanning waveforms,spectrums and scan line images of triangle waveform actuated scanning at several frequencies are tested. The test results show that the hysteresis behavior and the resonances affect scanning linearity seriously. An open loop control method is designed,which consists of a software hysteresis compensator and notch filters in serials. The comparison of scanning waveforms and scan line photos of triangle waveform actuated scanning with and without open loop controller shows that the scanning linearity is improved effectively. The scanning nonlinearities of 100 Hz and 400 Hz triangle wave scanning reduce to 2% and 7% respectively from 6% and 27%. The scanner realizes fast linear scanning..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 408 (2010)
Wavefront Closed Loop Correction for Entire Beam Path of Technical Integration Experiment Line
Dai Wanjun, Hu Dongxia, Yang Zeping, Zhou Wei, Zhao Junpu, Zhang Xin, Zhang Kun, Jiang Xuejun, Deng Wu, and Jing Feng
Each entire beam path static wavefront of technical integration experiment line (TIL) was obtained by the wavefront measurement system in the target chamber. The result was transited to wavefront sensor in the main amplifier diagnostic package. Based on the deformable mirror at the injection of main amplifier and the wEach entire beam path static wavefront of technical integration experiment line (TIL) was obtained by the wavefront measurement system in the target chamber. The result was transited to wavefront sensor in the main amplifier diagnostic package. Based on the deformable mirror at the injection of main amplifier and the wavefront sensor placed at the diagnostic package,the wavefront of entire beam path was corrected with closed loop. A charge coupled device (CCD) was placed at the target point to monitor the laser farfield. As result shows,the energy concentration had visible improvement. The method effectively improves control ability of laser facility entire beam wavefront by small deformable mirror which meets the requirement of physical experiment..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 414 (2010)
Effect of Confinement on the Capability of Laser Ignition
Xu Jiao, Wu Lizhi, Shen Ruiqi, Ye Yinghua, and Hu Yan
The confinement has important effects on the capability of laser ignition. It can affect the delay time and the ignition threshold of energetic materials. So it is of key importance in the design of laser ignition element. Experiments were done to research the effects of confinement on the ignition capability of B/KNO3The confinement has important effects on the capability of laser ignition. It can affect the delay time and the ignition threshold of energetic materials. So it is of key importance in the design of laser ignition element. Experiments were done to research the effects of confinement on the ignition capability of B/KNO3 and B/KNO3/ phenolic resin by the laser whose wavelength is 1.06 μm. Three kinds of confinement were used. They were air,K9 glass,and K9 glass deposited with copper film. The results show that when reactions occur near to the surface,gaseous products are confined by K9 glass,and the high external pressure will augment the ignition threshold of energetic materials and reduce the delay time. The effect of the K9 glass deposited with copper film is to enhance the plasma near the surface of energetic materials,which reduces the delay time but lowers the ignition threshold,because the copper film reflects a part of the laser and a big part energy of the laser is used to generate the copper plasma..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 418 (2010)
Experimental Investigation of Laser Coherent Combining Based on Active Segmented Mirror
Yang Ruofu, Yang Ping, and Shen Feng
The correcting performance on piston aberration of beams with adaptive optics-active segmented mirror in laser coherent combining is studied. The piston aberration is introduced by active segmented mirror drived by high voltage which is produced by signal generator and amplified by high voltage amplifier. The far-fieldThe correcting performance on piston aberration of beams with adaptive optics-active segmented mirror in laser coherent combining is studied. The piston aberration is introduced by active segmented mirror drived by high voltage which is produced by signal generator and amplified by high voltage amplifier. The far-field pattern with piston aberration is detected by high-speed CCD and the CCD data is processed by digital circuit to produce the close-loop voltage for correcting the introduced piston perturbation in real-time. This experiment performs close-loop correction in different piston perturbation. The experimental results show that the piston perturbation frequency of 50 Hz is efficiently controlled. System also can compensate the piston aberration above one wavelength and combining efficiency reaches 75%..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 424 (2010)
Beam Transmission
Study of Single-Photon Acquisition Probability Based on Hermite-Gaussian Beams
Bi Huining, and Ma Jing
Single-photon acquisition is the key technology of free-space quantum key distribution. Single-photon acquisition probability is very important. Based Hermite-Gaussian beams in TEM20,TEM02,TEM30,TEM03 and TEM11,the theoretical model of single-photon acquisition probability is established. And the probability in differeSingle-photon acquisition is the key technology of free-space quantum key distribution. Single-photon acquisition probability is very important. Based Hermite-Gaussian beams in TEM20,TEM02,TEM30,TEM03 and TEM11,the theoretical model of single-photon acquisition probability is established. And the probability in different modes is shown by numerical simulation. The physical model of time filtering is established,the limited mode and optimal mode are analyzed. The results can provide theoretical basis for the design of single-photon source,and optimize the system of free-space quantum key distribution..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 428 (2010)
Scaling Laws of High Energy Laser Propagation through Atmosphere
Qiao Chunhong, Fan Chengyu, Huang Yinbo, and Wang Yingjian
The scaling laws of high energy laser propagation through atmosphere are numerically analyzed by the four-dimension simulation program of high energy laser in atmosphere. The scaling relations of the 63.2% encircled energy beam radius spreading and the average energy intensity in the different encircled energy radius aThe scaling laws of high energy laser propagation through atmosphere are numerically analyzed by the four-dimension simulation program of high energy laser in atmosphere. The scaling relations of the 63.2% encircled energy beam radius spreading and the average energy intensity in the different encircled energy radius are obtained in the focal plane. The scaling relations are applicable to different atmospheric turbulence effects. Based on the relations,the atmospheric propagation effects of high energy laser can be predicted and estimated effectively..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 433 (2010)
Propagation Characteristic Research about Two Dimension Circle Waveguide Using a Variational Polar Coordinates Beam Propagation Method
Han Wenjie, Zhang Wenping, Li Li, Zhang Fangpei, Shen Yan, and Zheng Yongchao
A polar coordinates N-axis finite-difference beam propagation method (FD-BPM) based on a novel step-length setting mode has been deducted,and an idea named variational polar coordinates FD-BPM is advanced in this paper,which will bring higher precision,more convenient computation and analysis. Comprehensive analysis toA polar coordinates N-axis finite-difference beam propagation method (FD-BPM) based on a novel step-length setting mode has been deducted,and an idea named variational polar coordinates FD-BPM is advanced in this paper,which will bring higher precision,more convenient computation and analysis. Comprehensive analysis to the rigorous two-dimensional (2D) circle waveguide is achieved. When the light wave is transmitted in the waveguide with different curvatures,a maximum ratio of conductible mode energy to initial energy existing is discovered,and short wave is easier to be formed conductible mode compared with in the same waveguide. Furthermore,investigation about S shape and C shape waveguide has been performed in depth. The propagation capability of C shape waveguide is more excellent than S shape waveguide,as the latter has a higher tangent loss,whereas this distinction reduces while the curvature increasing. Some available propagation rules of S and C shape waveguide with different curvatures are described. The transparence boundary condition (TBC) is thought as practicable while using the polar coordinates N-axis FD-BPM presented in this paper to research the rigorous 2D circle waveguide. So-called boundary echo disturbance caused by TBC,is proved inexistent..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 438 (2010)
Two-Dimensional Axial Symmetric Fractional Fourier Transforms for Elliptical Gaussian Beams Employing Wigner Distribution Function
Chen Tianlu, Wu Ping, Li Haijin, Ciren Nima, Ning Changchun, Hu Haibing, and Gao Jiajie
With the elliptical gradient-index medium used as the optical system to implement two-dimensional axial symmetric fractional Fourier transforms (FRFT),the analytical formula of the beam width and the intensity distribution for two-dimensional axial symmetric fractional Fourier transform of elliptical Gaussian beams havWith the elliptical gradient-index medium used as the optical system to implement two-dimensional axial symmetric fractional Fourier transforms (FRFT),the analytical formula of the beam width and the intensity distribution for two-dimensional axial symmetric fractional Fourier transform of elliptical Gaussian beams have been derived,based on the equivalence between the rotation of the Wigner distribution function and the fractional Fourier transform. By employing the derived formula,the influence of the fractional order on the properties of elliptical Gaussian beams in the fractional Fourier transform plane has been studied in detail. The results indicate that the on-axis intensity and the beam width of elliptical Gaussian beams change asynchronously along the x,y axises and the two parameters are dependent on the fractional order px and py respectively. The circular Gaussian beams will be obtained in specific output plane. Meanwhile,it will appear that the beam width satisfies wx>wy in specific output plane in spite of wx
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 444 (2010)
Biomedical Photonics and Laser Medicine
Effects of Low-Level Laser Therapy on Cutaneous Wound Healings with Three Doses
Pan Zhenhua, Li Yingxin, Wang Xing, Chen Hongli, and Xiao Quanzhi
To observe the influences of different daily doses between 1-4 J/cm2 of low-level laser therapy (LLLT) on wound healings,the dorsal cutaneous excisional wounds of Wistar rats were irradiated with 630 nm at three daily doses of 1.2 J/cm2,2.4 J/cm2 and 3.6 J/cm2 under a constant power density of 10 mW/cm2. The analysis oTo observe the influences of different daily doses between 1-4 J/cm2 of low-level laser therapy (LLLT) on wound healings,the dorsal cutaneous excisional wounds of Wistar rats were irradiated with 630 nm at three daily doses of 1.2 J/cm2,2.4 J/cm2 and 3.6 J/cm2 under a constant power density of 10 mW/cm2. The analysis of variance (ANOVA) of areas of the wounds indicates that there were no statistical differences among the control group and the other three different doses groups. However,microscopic observations,both hematoxylin and eosin staining and Masson staining,could tell evidently better results of LLLT groups when compared to the control group,including the shorter period of inflammation,the greater development of granulations and collagens,and better epithelialization. The microscopic evaluations also suggest that larger dose brings better wound healing results within the 1-4 J/cm2 range..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 599 (2010)
Micro-Raman Spectra for Lipids C-H in Colorectal Tissue
Gao Zehong, Yu Jinggong, Liu Fuxiang, Hu Bo, and Michael Guiver
The purpose of this study is to investigate a relationship between the structure of lipid and colorectal carcinogenesis at the molecular level. Colorectal cancer specimens and adjacent normal tissues were measured using confocal Raman microscopy system. The bands at 2857 cm-1 and 2891 cm-1 originate from CH2 symmetric The purpose of this study is to investigate a relationship between the structure of lipid and colorectal carcinogenesis at the molecular level. Colorectal cancer specimens and adjacent normal tissues were measured using confocal Raman microscopy system. The bands at 2857 cm-1 and 2891 cm-1 originate from CH2 symmetric and asymmetric stretching vibrations,respectively. The band at 2938 cm-1 arises from symmetric C-H stretching vibrations. The results show that there are prominent differences between colorectal cancer specimens and adjacent normal tissues in Raman spectroscopy:1) The intensity of the bands of the cancer tissue spectrum at 2857 cm-1 and 2891 cm-1 are reduced compared with those of the normal spectra. The relative intensity of the band at 2938 cm-1 of lipid of colorectal cancer is stronger than that in normal tissues. 2) The average ratio (I2891 / I2857) values is reduced compared with those of the normal spectra. The values for normal and cancerous tissues are 2.21 and 1.69 by the function of ‘compare means’ of SPSS16.0 software. The research results demostrated that the lateral packing of lipids is loosened which may result in the fluidity of lipid to be increased and the interactions of lipid and protein increase when normal cells are transformed into cancerous cells. Our data suggested there is the relationship between the stretch vibrations of lipids and colorectal carcinogenesis..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 605 (2010)
Holography and Information Processing
Lossless Compression of Digital Speckle Images Based on Speckle Correlation
Li Donghui
Compression of speckle images is significant to storage reduction of measurement systems. We propose a coder for lossless compression of laser speckle images,which is based on speckle displacement estimation,temporal prediction and the Golomb coding. Firstly,speckle displacements are estimated for each subblock. Next,aCompression of speckle images is significant to storage reduction of measurement systems. We propose a coder for lossless compression of laser speckle images,which is based on speckle displacement estimation,temporal prediction and the Golomb coding. Firstly,speckle displacements are estimated for each subblock. Next,according to correlation properties of dynamic speckle,we set up the prediction model which predicted current pixels model. Finally,prediction errors are coded by the Golomb coding. Key features of the proposed speckle image coder include the estimation of speckle displacement by digital speckle image correlation method and the prediction modeling based on the extremum of the dynamic speckle correlation function. Experimental results show that the proposed coder provides good improvement in compression coding efficiency of laser speckle images..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 484 (2010)
Camera Lens Distortion Correction Based on Coplanar Point Direct Liner Transformation
Ge Baozhen, Li Xiaojie, and Qiu Shi
The direct linear transformation (DLT) based on the ideal perspective transformation model can obtain the mapping matrix between the two-dimensional (2D) image coordinates and the three-dimensional (3D) coordinates by solving the linear equations. The method is simple and fast,but it does not take the effect of lens diThe direct linear transformation (DLT) based on the ideal perspective transformation model can obtain the mapping matrix between the two-dimensional (2D) image coordinates and the three-dimensional (3D) coordinates by solving the linear equations. The method is simple and fast,but it does not take the effect of lens distortion into consideration. In order to correct the distortion in an easy way,this paper takes full account of the lens distortion on the basis of coplanar point linear solution. After initial parameters determined according to the camera information,transformation matrix and distortion coefficient are modified continuously by least-squares method to obtain the optimal parameters,and use data points pair of different location distribution to verify that the distortion coefficient calibrated by the method is relative independence. Finally,square image obtained by the camera was selected and corrected using the distortion coefficient gained by the above-mentioned method. The results have improved significantly and verified the validity of the method..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 488 (2010)
Contour Extraction of Image Using Adaptive Bilinear Generalized Fuzzy Enhancement
Zheng Dezhong, and Cui Fayi
A new linear generalized fuzzy operator (LGFO) used for fuzzy enhancement of regional contrast is constructed based on the theory of traditional fuzzy set (FS) and generalized fuzzy set (GFS),and theoretical analyses and testing the characters LGFO. And then an algorithm for adaptive bilinear generalized fuzzy enhancemA new linear generalized fuzzy operator (LGFO) used for fuzzy enhancement of regional contrast is constructed based on the theory of traditional fuzzy set (FS) and generalized fuzzy set (GFS),and theoretical analyses and testing the characters LGFO. And then an algorithm for adaptive bilinear generalized fuzzy enhancement used for extracting edge contour of images is put forward. The algorithm is to achieve space transform between gray image space and generalized fuzzy space by using linear generalized membership transform function and LGFO. Using the algorithm,the linear generalized fuzzy membership space is enhanced fuzzily by LGFO in the process of space transform. Finally,the contour of image is extracted using “MIN” operator in gray image space. The algorithm is also to achieve adaptive optimization of the image after linear generalized fuzzy enhancement by selecting fuzzy parameter D automatically,using the quotient between detectable edge degree and noise standard deviation as the evaluation standard of image enhancement. The experiments show that the algorithm is efficient and has no distortion,and can be applied to color image. By using the algorithm,the contour of image is accurate and structured..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 495 (2010)
Gene Chip Microarray Fluorescent Spots Images CCD Scanning and Acquiring System
Liu Jun, Zhao Jibin, Liu Weijun, and Wang Tianran
To promote the efficiency of microarray gene chip images scanning and acquiring,a microarray fluorescent spots images scanning system is developed,in which an epi-fluorescence microscope,a precision three-dimensional (3D) translation motion platform,and a thermo electric cooling CCD camera are integrated effectively toTo promote the efficiency of microarray gene chip images scanning and acquiring,a microarray fluorescent spots images scanning system is developed,in which an epi-fluorescence microscope,a precision three-dimensional (3D) translation motion platform,and a thermo electric cooling CCD camera are integrated effectively to construct an imaging and scanning mechanism. This system utilizes the industrial personal computer (IPC) as the core of measurement and control and realizes three specific functions,such as microscope auto focusing control,fluorescent spots images auto scanning and sampling and microarray spots images stitching. Many assays and experiments have been preformed to manifest that the system can effectively promote the efficiency of the microarray polymerase chain reaction (PCR) experiments and analysis..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 505 (2010)
Target Reconstruction Algorithm for Streak Tube Imaging Lidar
Sun Jianfeng, Wei Jingsong, Liu Jinbo, Gao Jian, and Wang Qi
Streak tube imaging lidar (STIL) is a new type of flash laser radar,and its receiving detector is the transient optical streak tube. The characteristic of STIL is of wide field of view and high resolution. It has two types,single slit and multiple slits. Because the streak tube can not directly output the four-dimensioStreak tube imaging lidar (STIL) is a new type of flash laser radar,and its receiving detector is the transient optical streak tube. The characteristic of STIL is of wide field of view and high resolution. It has two types,single slit and multiple slits. Because the streak tube can not directly output the four-dimensional image (three-dimensional (3D) range image and one-dimensional (1D) intensity image),for the streak images of the two types,peak-detection algorithm is used to reconstruct the far-distance target in this paper. And the complete four-dimensional images of STIL are obtained. The experiment results show that STIL is an imaging device of high resolution and high frame frequency,so it will have promising application..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 510 (2010)
An Improved Denoising Method for 4f Optical System Based on Bilateral Filter
Qiu Yu, Tian Fengchun, Chen Jianjun, and Li Peng
In optical 4f system with coherent illumination source,the output images are easily contaminated by dusts and spots in the surface of lens and charge coupled device (CCD). With the image degradation factors being classified by additive stochastic noise,spots,illumination ununiformity and system low-pass characterizatioIn optical 4f system with coherent illumination source,the output images are easily contaminated by dusts and spots in the surface of lens and charge coupled device (CCD). With the image degradation factors being classified by additive stochastic noise,spots,illumination ununiformity and system low-pass characterization,a simplified model is proposed. The output result is used as apriori information when the input is a full white image to calculate the distribution of spots and illumination ununiformity of which stabilization is assumed in an experiment. An improved adapted bilateral filter is therefore introduced to denoise and remove spots. The optical and synthetic image experiments show that the proposed method can effectively reduce noise and restore image with edge sharpness being preserved. The robust characterization of the proposed method is embodied by the simulation results even under the serious spot-contamination circumstance..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 514 (2010)
Laser Manufacturing
Microstructure and Properties of Laser Weld Joints of Reduced Activation Martensitic Steel
Wu Xiaohu, Zhao Fei, Xie Wenjia, Lv Changwei, and Liang Renjin
Laser welding experiment was done on the reduced activation martensitc steel which is used in fusion reactor,the microstructure and mechanical properties of the welding joint were tested in this paper. The results show that the joints with good quality can be obtained by laser welding. The microstructure in weld is latLaser welding experiment was done on the reduced activation martensitc steel which is used in fusion reactor,the microstructure and mechanical properties of the welding joint were tested in this paper. The results show that the joints with good quality can be obtained by laser welding. The microstructure in weld is lath martensite,while the heat affect zone (HAZ) comprised coarse grain zone and fine grain zone. The structure of coarse grain zone is coarse pearlite and a mixed structure which comprises fine pearlite and ferrite in fine grain zone. The hardness of the weld was about 530 HV,while minimum hardness was about 220 HV in HAZ. The tensile strength of the weld joint reached 775 MPa..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 577 (2010)
Three-Dimensional Characterizing Technique for Geometrical Features of Single Laser Cladding
Wang Zhijian, Dong Shiyun, Xu Binshi, Xia Wei, and Yan Shixing
In order to control accurately clad shape of laser cladding for remanufacturing parts,it is necessary to build the three-dimensional (3D) model of single laser cladding. In this study,single track laser cladding experiment was executed on 18Cr2Ni4WA steel substrate by using Nd∶YAG laser. The cross-section shape of cladIn order to control accurately clad shape of laser cladding for remanufacturing parts,it is necessary to build the three-dimensional (3D) model of single laser cladding. In this study,single track laser cladding experiment was executed on 18Cr2Ni4WA steel substrate by using Nd∶YAG laser. The cross-section shape of cladding metal was modeled by AutoCAD and a 3D geometric model of single laser clad was built. The model consists of two partial sphere located in two terminals and partial cylinder located in the middle of the single tract cladding. In order to character accuracy of the model,the weights of theoretical and experimental structure were compared. The result shows that top profile of cross-section was nearly a circular arc,and the weight of theoretical structure was almost equal to that of experimental structure. The model can characterize commendably the geometrical features of experimental laser cladding..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 581 (2010)
Study on Processing Strategy of Complicated Doubly Curved Surface in Laser Forming
Shi Yongjun, Liu Yancong, Yao Zhenqiang, and Hu Jun
In engineering applications,some components are composed of doubly curved shapes. It is of significance for investigations on processing strategy of complicated doubly curved surface in laser forming. However,as a dieless forming technique,laser heating paths are not necessarily directly related with the desired shape,In engineering applications,some components are composed of doubly curved shapes. It is of significance for investigations on processing strategy of complicated doubly curved surface in laser forming. However,as a dieless forming technique,laser heating paths are not necessarily directly related with the desired shape,which raises the degree of difficulty for process planning. To acquire high accurate shape with doubly curved in laser forming,a new design approach is proposed to determine path planning and process parameters based on the studies of cross heating and pre-bend in this paper. Firstly,a strain field required to obtain a desired shape from a planar shape is obtained. Secondly,the heating paths are planned in the top and the bottom surface separately. Thirdly,the basic relationship databases of the flat and curved plate between process parameters and residual plastic strain and between process parameters and strain ratio of the top and bottom surfaces are built,respectively. Finally,the heating condition is determined according to the required strain field and the basic relationship databases. The experimental result based on the above process strategy shows that the laser forming shape is approximately consistent with the desirable shape..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 586 (2010)
Microstructure and Phase Structure of Laser Solid Forming Ti2AlNb-Based Alloy
Chen Jing, Jiang Guozheng, Lin Xin, and Huang Weidong
Ti2AlNb-based alloys of two different compositions were deposited using a 5 kW CO2 laser. Optical microscope (OM),scanning electron microscope (SEM),energy-dispersive spectrometer (EDS),X-ray diffraction (XRD) and microhardness testing method,were used to investigate the typical microstructure evolution,phase transformTi2AlNb-based alloys of two different compositions were deposited using a 5 kW CO2 laser. Optical microscope (OM),scanning electron microscope (SEM),energy-dispersive spectrometer (EDS),X-ray diffraction (XRD) and microhardness testing method,were used to investigate the typical microstructure evolution,phase transformation and the corresponding hardness evolution. Experimental results show that for Ti-20%Al-27%Nb (atomic fraction) (A1),the phase transformation occurrs:B2→B2+O→B2 along the laser deposition direction. While Ti-22%Al-27%Nb (A2) is mainly composed of β(TiNb) dendritic and B2+O in the interdendritic. The primary dendrite trunk spacing changes from 25 μm to 80 μm along the deposition direction. For the two different compositions Ti2AlNb-based alloys,the microhardness variation of A1 alloy along the deposition direction is low→high→low,which agrees well with the corresponding microstructure and phase transformation. The microhardness of A2 alloy distributes uniformly except the local region of the dendritic..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 593 (2010)
Materials and Thin Films
Near- and Mid-Infrared Spectroscopic Properties of Tm3+-Doped Ge-Ga-S-CsI Glasses
Zhang Pengjun, Dai Shixun, Peng Bo, Xu Tiefeng, Nie Qiuhua, Zhang Xianghua, and Wang Xunsi
Tm3+-doped chalcogenide glasses in Ge-Ga-S-CsI system were prepared and the properties of glasses including density,absorption spectrum,emission spectra and fluorescence life in the near- and mid-infrared spectral region under 800 nm excitation were measured. The optical parameters such as intensity parameter Ωi (i=2,4Tm3+-doped chalcogenide glasses in Ge-Ga-S-CsI system were prepared and the properties of glasses including density,absorption spectrum,emission spectra and fluorescence life in the near- and mid-infrared spectral region under 800 nm excitation were measured. The optical parameters such as intensity parameter Ωi (i=2,4,6),predicted spontaneous A,radiative transition rate β and lifetime τrad of Tm3+ in Ge-Ga-S-CsI glasses and so on by means of Judd-Ofelt theory according to absorption spectrum were calculated. The fluorescence spectra were investigated with the different Tm3+ ion concentration under 800 nm excitation. Also,the emission cross-section at 1.8 μm and 3.8 μm was found using the theory of McCumber and the Futchbauer- Ladenburg equation respectively..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 554 (2010)
Theoretical Research of Photoelectric Properties of Monoclinic VO2 Material
Wang Xiaozhong, He Jie, Liu Qiang, Song Tingting, Wang Linglong, Guo Yingjie, and Lin Libin
Electronic structure and photoelectrical properties of monoclinic VO2 are studied with self consistent of charge-discrite variation-embedded cluster model (SCC-DV-Xα-ECM) method. The results show that the energy gap is 0.4411 eV and Fermi energy level is 0.00365 eV above the center of energy gap and is close with conduElectronic structure and photoelectrical properties of monoclinic VO2 are studied with self consistent of charge-discrite variation-embedded cluster model (SCC-DV-Xα-ECM) method. The results show that the energy gap is 0.4411 eV and Fermi energy level is 0.00365 eV above the center of energy gap and is close with conduction band,as accords with the experimental data very well. The total energy of monoclinic VO2 (-568.18 eV) is lower than the one of rutile VO2 (-470.33 eV),so it can undergo a transition into the later with external energy such as increasing temperature. Absorption coefficient accords with the experimental data in the low frequencies and conductance is consistent with other theoretical analysis in 2.5-13.5 eV..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 560 (2010)
Effect of the Structure Shape on the 8-Fold Photonic Quasicrystals
Yin Jianling, Huang Xuguang, Liu Songhao, and Liu Jun
The effect of the cylinder shape and symmetry of two-dimensional 8-fold photonic quasicrystals (PQCs) is numerically investigated using the finite difference time domain (FDTD) method. Results indicate that,when the fill factor remains:i) the property that the bandgap is independent on the direction can be remained;ii)The effect of the cylinder shape and symmetry of two-dimensional 8-fold photonic quasicrystals (PQCs) is numerically investigated using the finite difference time domain (FDTD) method. Results indicate that,when the fill factor remains:i) the property that the bandgap is independent on the direction can be remained;ii) the lower the symmetry of the cylinder shape is,the narrower the bandgap of 8-fold PQCs is. The reduction of the band gap is negligibly small for the hexagon and square cylinder while it reduces more for the triangle cylinder;iii) the lower the symmetry of the ellipse cylinder shape is,the narrower the bandgap of 8-fold PQCs is. However,the variant of the bandgap is very gently..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 567 (2010)
Study of the Evaluation Parameter of Optical Components before and after Coating in the High Power Laser System
Hu Dafei, Shao Shuying, Fang Ming, Qi Hongji, and Yi Kui
The surface figures of 120 mm×88 mm samples were measured by ZYGO Mark Ⅲ-GPI interferometer before and after coating. The analyzed of peak to valley (PV) and gradient of root mean square (GRMS) show that PV and GRMS increased,respectively,after deposition. At the same time,GRMS increased with the increase of PV,whThe surface figures of 120 mm×88 mm samples were measured by ZYGO Mark Ⅲ-GPI interferometer before and after coating. The analyzed of peak to valley (PV) and gradient of root mean square (GRMS) show that PV and GRMS increased,respectively,after deposition. At the same time,GRMS increased with the increase of PV,which also can be confirmed from the theoretical calculation. In addition,the power spectral density (PSD) of several samples are also shown. The results indicate that the curves ascend after coating,which relates closely with the substrate and deposition condition..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 572 (2010)
Measurement and Metrology
Detector Array for Measuring Far-Field Power Density Distribution of Mid-Infrared Laser
Yang Pengling, Feng Guobin, Wang Zhenbao, Wang Qunshu, Feng Gang, and Zhang Tianqing
Beam quality and intensity are critical characters of high energy laser system. Accurately measuring the far-field laser beam spatial profile is an effective way to diagnose laser beam quality and study the atmospheric transmission effects for a high energy laser system. In this paper,a detector array system for mid-inBeam quality and intensity are critical characters of high energy laser system. Accurately measuring the far-field laser beam spatial profile is an effective way to diagnose laser beam quality and study the atmospheric transmission effects for a high energy laser system. In this paper,a detector array system for mid-infrared laser beam profile measuring is developed. The system is consisted of optic attenuators,photoconductive HgCdTe detectors,amplifiers,analog to digital converter unit,wireless transmission unit,and data processing end. Considering the responsivity and resistance sensitivity of HgCdTe detector with temperature,a responsivity adaptive calibration model is proposed to solve the temperature sensitivity of HgCdTe detector. The system is capable for absolutely measuring far-field power density distribution of infrared laser with response wavelength between 1 μm and 5 μm,the dynamic range of power density which it can measure of above 103,the refresh rate of 25 Hz,along with the measurement uncertainty of less than 20% in the temperature range of -60-40 ℃..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 521 (2010)
Real-Strain Measurement of Low-Dimensional Materials Based on Digital Image Tracking
Wang Wei, Xiao Jianqiang, and He Xiaoyuan
In order to obtain the real-strain of low dimensional materials,the real-strain measurement of low-dimensional materials based on digital image tracking has been proposed. First,the speckles pre-made on the sample or its surface feature points are taken as the tracking objects. Two points are successfully tracked in thIn order to obtain the real-strain of low dimensional materials,the real-strain measurement of low-dimensional materials based on digital image tracking has been proposed. First,the speckles pre-made on the sample or its surface feature points are taken as the tracking objects. Two points are successfully tracked in the real-strain measurement by adopting the improved image correlation formula and selecting the correlative matched template and search region that are determined by analyzing the deformation characteristic of low-dimensional materials. By using the arithmetic of bilinear inter value,the objective is orientated in the 0.01 pixel location,so the measurement precision has been improved. Then,the loads are exerted at grade step. The objects can be successfully tracked. And,the real-strain value under the correlative loads has been obtained. Furthermore,it is an experiment method for studying the dynamic mechanics of low-dimensional materials. The experiment shows that the tracking technology can be fully applied in the real-strain measurement of low-dimension materials. Moreover,the method is also applied in the real-strain measurement of different distances between two speckles. And,the relative calculation error is controlled in 5%..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 526 (2010)
Study on Phase Retrieval from Single Close Fringe Pattern with High Precision
Liu Dong, Yang Yongying, Tian Chao, Luo Yongjie, and Zhuo Yongmo
Different modulation methods can be adopted in interferometry and the desired information can be obtained with the interferograms. But sometimes the very nature of the experimental setup does not allow us to introduce any modulation method. Then we are forced to demodulate the interferograms with close fringes. RegularDifferent modulation methods can be adopted in interferometry and the desired information can be obtained with the interferograms. But sometimes the very nature of the experimental setup does not allow us to introduce any modulation method. Then we are forced to demodulate the interferograms with close fringes. Regularized phase-tracking (RPT) method can demodulate close fringes but with low precision. This paper presents a novel algorithm,called RPT approached & golden section algorithm (RPT&GS),to demodulate close fringes based on the RPT method. Starting from the result of classical RPT,we use the golden section algorithm to search for the accurate phase of single close fringe. Computer simulation shows the RPT&GS contains all the advantages of RPT besides high demodulation precision. Comparison experiments show good agreement with ZYGO GPI interferometer on real close fringes,and the average peak-valley (PV) value accuracy is better than λ/20..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 531 (2010)
Numerical Analysis of Laser-Generated Lamb Waves by Finite Element Method in Time and Frequency Domain
Sun Hongxiang, and Xu Baiqiang
Based on the theory of plane strain and the elastic equations of dynamic equilibrium,the equations of dynamic equilibrium in the frequency domain are derived. The finite element models of laser-generated Lamb waves in the time and frequency domain are established for elastic material. Based on the numerical calculationBased on the theory of plane strain and the elastic equations of dynamic equilibrium,the equations of dynamic equilibrium in the frequency domain are derived. The finite element models of laser-generated Lamb waves in the time and frequency domain are established for elastic material. Based on the numerical calculations,the solving process of the two models is compared. Moreover,the characteristics of laser-generated Lamb waves on a thin viscoelastic plate are analyzed in the frequency domain. The results show laser-generated Lamb waves mainly include the lower frequency components of the weak dispersion symmetric mode and the dispersive anti-symmetric mode. The propagation of laser-generated Lamb waves on viscoelastic materials can be calculated effectively by the finite element model in the frequency domain. In addition,the amplitudes of Lamb waves are attenuated in the viscoelastic material,and the attenuation coefficients to different modes of the wave are different..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 537 (2010)
A Method of Curvature Measurement Based on Charge Coupled Device Dual-Laser Collimation
Lu Quan, Han Baojun, Liu Shangqian, and Wang Huifeng
To meet the requirement for the high accuracy curvature measurement of special pipe,a method based on charge coupled device (CCD) dual-laser collimation is proposed. The curvature measurement theories based on both CCD single-laser collimation and dual-laser collimation are introduced. A dynamic rotation model of targeTo meet the requirement for the high accuracy curvature measurement of special pipe,a method based on charge coupled device (CCD) dual-laser collimation is proposed. The curvature measurement theories based on both CCD single-laser collimation and dual-laser collimation are introduced. A dynamic rotation model of target is established,and the rotation angle is extracted accurately by the pinpoint method of the dual-laser spots and field calibration method of the concentric circles. Finally,the accurate curvature of special pipe is acquired after correcting the measurement results. Experimental results show that the amplitude errors is ±0.01 mm,and the azimuth angle errors is ±10″. This method is quite stable and accurate,which can meet the requirement for the high accuracy curvature measurement of special pipe..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 543 (2010)
Vibration Measurement System Based on a Highly Stabilized Fiber 3×3 Coupler Interferometer
Li Min, Xie Fang, and Chen Zhimin
A highly stabilized fiber 3×3 coupler Michelson interferometer vibration measurement system,which employs fiber Bragg gratings to interleave two fiber Michelson interferometers that share the common interferometric-optical-path,is presented. One interferometer uses an electronic feedback loop to compensate for theA highly stabilized fiber 3×3 coupler Michelson interferometer vibration measurement system,which employs fiber Bragg gratings to interleave two fiber Michelson interferometers that share the common interferometric-optical-path,is presented. One interferometer uses an electronic feedback loop to compensate for the low frequency drift in the phase of the interferometric signal which is resulted from environmental disturbances,while the other one uses another electronic feedback loop to track the phase variation induced by the measured vibration,and thus the amplitude measurement of the vibration and the vibration direction are measured simultaneously. The results show that the measurement system is designed to be capable of measurement vibration with frequencies ranging from 0.1 Hz to 200 Hz and the measurement sensitivity is 6 μm/V..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 549 (2010)
Optical Communication
Dispersion Compensation in Ultra-Short Optical Pulse Compressing System and Transmitting System
Qu Kenan, Zhang Weigang, Liu Zhuolin, Shen Heng, and Zhang Leilei
An initial ultra-short optical pulse compression system is designed based on normal single-mode fiber and hollow photonic crystal fiber (PCF). By approximately solving the nonlinear Schrdinger equation of the optical pulse evolution in fibers,the frequency chirp compensation of second-order and third-order dispersion An initial ultra-short optical pulse compression system is designed based on normal single-mode fiber and hollow photonic crystal fiber (PCF). By approximately solving the nonlinear Schrdinger equation of the optical pulse evolution in fibers,the frequency chirp compensation of second-order and third-order dispersion is studied in ultra-short pulse compression system and transmission system,and the mechanism of self-phase modulation (SPM) compensating dispersion is analyzed. It is found that,in ultra-short pulse compression system,the second-order dispersion compensation experiences nonlinear processes,and at the same time the third-order dispersion compensation experiences the opposite processes. But the pulse compression quality decreases seriously at the last process..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 449 (2010)
Analysis and Optimum of a Novel Arrayed-Waveguide Grating
Wang Youbin, and Huang Xuguang
A novel arrayed-waveguide grating (AWG) based on unbent waveguides is analyzed. The arrayed waveguides are replaced by unbent waveguides and two graded-index planar waveguides (GISLAB) are used as input and output planar waveguides,respectively. This design can decrease the size of the coarse wavelength division multipA novel arrayed-waveguide grating (AWG) based on unbent waveguides is analyzed. The arrayed waveguides are replaced by unbent waveguides and two graded-index planar waveguides (GISLAB) are used as input and output planar waveguides,respectively. This design can decrease the size of the coarse wavelength division multiplexing (CWDM) effectively. A mathematical model of the AWG is established based on the theory of Fourier optics and wave optics,with reasonable parameters considering every factor. The novel arrayed waveguide grating with asymmetric focal lengths of GISLABs is discussed,whose background noise is degraded by 20 dB with respect to the symmetrical structure,and which will widen spectral width. The method of reducing the size further with a reflector and the property of the routing is designed..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 454 (2010)
A Research of PPWM Modulation Scheme′s Power Spectrum and Its Modified Scheme
Bai Bo, Fan Yangyu, Yuan Mengjie, and Tan Qinggui
After analysis of the L-level pulse-position-width modulation (PPWM) scheme′s power spectrum,strong spectral lines in the PPWM sequence are found,which are not good for the propagation of the sequences. In this paper,the PPWM modulation scheme is modified,and a new modulation scheme,L-level pulse-width-position modulatAfter analysis of the L-level pulse-position-width modulation (PPWM) scheme′s power spectrum,strong spectral lines in the PPWM sequence are found,which are not good for the propagation of the sequences. In this paper,the PPWM modulation scheme is modified,and a new modulation scheme,L-level pulse-width-position modulation scheme (PWPM) is proposed. This scheme lowers the peak value power,scatters the power spectrum,and at the same time has the same power efficiency,bandwidth efficiency and packet error rate as PPWM modulation scheme..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 460 (2010)
Performance Comparsion between On-Off Keying and Orthogonal Frequency Division Multiplexing Signals in 40 GHz Radio-Over-Fiber Systems
Wang Wenpei, Chen Lin, Dong Ze, Cao Zizheng, Lu Jia, and Yu Jianjun
The transimission performance of on-off keying (OOK) and orthogonal frequency division multiplexing (OFDM) signals in radio-over-fiber (ROF) system is experimentally and theoretically studied. The theoretical results show that OFDM signal is almost not affected by inter-symbol interference (ISI),only with the phase chaThe transimission performance of on-off keying (OOK) and orthogonal frequency division multiplexing (OFDM) signals in radio-over-fiber (ROF) system is experimentally and theoretically studied. The theoretical results show that OFDM signal is almost not affected by inter-symbol interference (ISI),only with the phase changed,where as OOK signal is seriously affected by ISI. The experiment results show that the eye diagram of 2.5 Gb/s OOK signal is closed when transmitting over 60 km in single mode fiber (SMF),and its bit error rate (BER) can only reach 10-3. The constellation of OFDM is clear when ttransmitting over 130 km with BER of 10-4. All theoretical and experimental results show that the performance of OFDM is better than that of OOK in ROF system..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 465 (2010)
Digitalized Optical Coherent Detection of Differential Phase Shift Keying Signal and Chromatic Dispersion Compensation
Feng Yong, Wen He, Zhang Hanyi, and Guo Yili
An optical 90° hybrid based on fiber passive devices is developed to enable optical coherent detection. By introducing the optical phase difference monitoring and control,the hybrid is stabilized over 12 hours without apparent deterioration. With the help of this hybrid,the differential phase shift keying (DPSK) sAn optical 90° hybrid based on fiber passive devices is developed to enable optical coherent detection. By introducing the optical phase difference monitoring and control,the hybrid is stabilized over 12 hours without apparent deterioration. With the help of this hybrid,the differential phase shift keying (DPSK) signal is demodulated by mixing signal light with local light,and then,is sampled and digitalized by high-speed Analog-to-digital converters(ADCs). Off-line algorithm is used to estimate the phase error between the signal light and local light and compensate chromatic dispersion. We restore the constellation diagrams of 8 Gb/s DPSK signal transmited over 90 km single mode fiber using FIR filter to compensate the fiber dispersion and get an error free result in our experiment..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 471 (2010)
Application of Ant Colony Algorithm in Analyzing of Traverse Uniform Strain Reflective Spectrum of Fiber Bragg Grating
Wu Fei, Kuang Minmin, Zhao Jing, and Zhang Ying
When the transverse force was measured by using fiber Bragg grating (FBG),some parameters,hard to be measured,influenced severely the reflective spectral model of FBG. Therefore,ant colony algorithm was proposed in analyzing the traverse uniform strain reflective spectral model of FBG. Base on the traverse uniform straWhen the transverse force was measured by using fiber Bragg grating (FBG),some parameters,hard to be measured,influenced severely the reflective spectral model of FBG. Therefore,ant colony algorithm was proposed in analyzing the traverse uniform strain reflective spectral model of FBG. Base on the traverse uniform strain sense theory of FBG and ants algorithm,the objective function in analyzing traverse uniform strain reflective spectrum of FBG is established,meanwhile corresponding experimental system is constructed. Aiming at the parameters combination from the experimental results,traverse loaded reflective spectrum of FBG is reconstructed using the ant colony algorithm. Experimental data showed that ant colony algorithm used in analyzing of traverse uniform strain reflective spectrum expression of FBG,had some advantages,such as high accuracy,stability and fast convergence rate. And some main parameters influenced the reflective spectrum could obtained easily..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 477 (2010)
Reviews
Liquid Crystal Beam Steering Technologies
Zhang Jian, Fang Yun, Wu Liying, and Xu Lin
Novel laser beam steering technologies are capable of steering a laser beam in real-time and programmable fashion. The precision non-mechanical agile beam steering system based on liquid crystals can be established in a way of small size,light weight,and low power consumption. The research progresses of beam steering tNovel laser beam steering technologies are capable of steering a laser beam in real-time and programmable fashion. The precision non-mechanical agile beam steering system based on liquid crystals can be established in a way of small size,light weight,and low power consumption. The research progresses of beam steering technologies at home and abroad are summarized. The principle and some key technologies of beam steering system based on liquid crystal are introduced. Taking the self-maded liquid crystal optical phased array (LCOPA) as example,the factors that affect diffraction efficiency of the device are analyzed,the methods that design and optimize the device are explained and discussed. The ways that improve the features of LCOPA are summarized including response time,dispersion,and broadband beam steering et al. The research trend of beam steering technologies based on liquid crystal is previewed..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 2, 325 (2010)
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