Journals >Chinese Journal of Lasers
Contents
2015
Volume: 42 Issue 9
51 Article(s)
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Research Article
Progress in Optical Focusing Techniques Aiming to Suppress Scattering Effect in Biomedical Tissues
Yang Qiang, Cao Liangcai, and Jin Guofan
The light passing through lens cannot be directly focused inside biomedical tissues at depth deeper than 1 mm due to strong scattering, which fundamentally limits the use of imaging techniques such as confocal microscopy and two-photon microscopy, since these techniques demand confined light focusing inside tissues. ToThe light passing through lens cannot be directly focused inside biomedical tissues at depth deeper than 1 mm due to strong scattering, which fundamentally limits the use of imaging techniques such as confocal microscopy and two-photon microscopy, since these techniques demand confined light focusing inside tissues. To suppress the effect of light scattering in tissues and focus light deeper, the optical wavefront illuminating tissues should be modulated. To this end, three kinds of techniques are proposed: the wavefront shaping technique which uses the optical intensity in the wanted light-focused zone as the feedback; the time-reversed technique which combines acousto- optic modulation with optical phase conjugation aiming to focus light inside tissues; the technique of measuring transmission matrix of scattering media. These three techniques are reviewed and compared, while a technical prospect is given as for their biomedical applications..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 901001 (2015)
Numerical Simulation of High Intensity of Laser Induced Plasma Shock Wave in Water
Lu Jianying, Geng Desheng, and Chen Lang
Laser-induced plasma formation and shock wave generation mechanism are our concern problems in investigating high intensity laser pulse focusing into water. A high speed schlieren photography technique with double-pulse lasers is used as a background light source, and the temporal and spatial evolution of shock wave arLaser-induced plasma formation and shock wave generation mechanism are our concern problems in investigating high intensity laser pulse focusing into water. A high speed schlieren photography technique with double-pulse lasers is used as a background light source, and the temporal and spatial evolution of shock wave are obtained. A two- phase computation model is established in consideration of water vaporization, plasma absorption laser pulse energy. The processes of laser induced plasma shock wave in water are numerically simulated. A reasonable agreement is obtained between experimental and simulation results. The shock wave propagation characteristics are studied，and comparison between simulation results and theoretical predictions are presented. The results show that the shock wave speeds in the initial stages of laser induced breakdown in water is up to 5 km/s, and pressure is up to a dozen GPa. Shock wave velocity and pressure decay rapidly over time, which decrease to acoustic speed in an 1 μs later after breakdown..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 902001 (2015)
Optimal Design of Single-Frequency Laser System for 795 nm Squeezed Light Source
Li Zhixiu, Yang Wenhai, Wang Yajun, and Zheng Yaohui
By using an extra-cavity-enhanced frequency doubler with a periodically poled KTiOPO4 (PPKTP) crystal, which is pumped by a home-made continuous-wave single-frequency tunable Ti: sapphire laser at 795 nm wavelength, the 397.5 nm violet laser is obtained experimentally with the output power of 103 mW, conversion efficieBy using an extra-cavity-enhanced frequency doubler with a periodically poled KTiOPO4 (PPKTP) crystal, which is pumped by a home-made continuous-wave single-frequency tunable Ti: sapphire laser at 795 nm wavelength, the 397.5 nm violet laser is obtained experimentally with the output power of 103 mW, conversion efficiency of 39.6%, and the beam quality factor M2<1.43. Compared with the intracavity enhanced frequency doubling with the angle matched Bismuth Triborate (BIBO) crystal, the mode matching efficiency of the 397.5 nm lasing to the optical parametric amplifier (OPA) cavity is increased from 76% up to 99%. Meanwhile, in the balanced homodyne detection system, a mode cleaner with the same cavity parameters as OPA, is inserted into the local oscillator to make sure the local oscillator and the signal fields have the identical spatial modes. As a result, the interference efficiency of the two input fields is more than 99%, and the efficiency of the balanced homodyne detection system is improved. By optimizing the design of the 795 nm and 397.5 nm laser system, the laser source can meet the requirement of studying the compact continuous-variable squeezed light source at 795 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 902002 (2015)
High-Power All-Fiber Mid-Infrared Supercontinuum Generation Pumped by Noise-Like Pulses
Liu Kun, Shi Hongxing, Liu jiang, Tan Fangzhou, Zhou Guanrui, and Wang Pu
A high-power all-fiber mid-infrared (mid-IR) supercontinuum (SC) generation in a single-mode ZBLAN fiber pumped by amplified noise-like pulses is reported. The mid-IR SC system is a 2 μm master oscillator power amplifier (MOPA) construction including a seed source and two-stage single-mode thulium-doped fiber amplifierA high-power all-fiber mid-infrared (mid-IR) supercontinuum (SC) generation in a single-mode ZBLAN fiber pumped by amplified noise-like pulses is reported. The mid-IR SC system is a 2 μm master oscillator power amplifier (MOPA) construction including a seed source and two-stage single-mode thulium-doped fiber amplifier (TDFA) followed by a single-mode ZBLAN fiber. A noise-like pulse fiber oscillator with wavepacket width of 1.4 ns and repetition rate of 3.36 MHz at 1966 nm is used as a seed source of mid-IR SC system. In the last stage TDFA, a SC covering from 1.9 to 2.4 μm with maximum output power of 28.5 W is generated. Then, the output SC of TDFA is injected into a 10 m single-mode ZBLAN fiber for further spectrum broadening. At last, a mid-IR SC covering from 1.9 to 3.62 μm with the maximum output power of 14.3 W is generated..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 902003 (2015)
Conduction Cooling and Compact，High Peak-Power，Nanoseconds Pluse Lasers
Xie Yin, Meng Junqing, Zu Jifeng, and Chen Weibiao
A master oscillator power amplifier (MOPA) structure based on Nd∶YAG microchip and Nd∶YVO4 slab is reported. The master oscillator is a passive Q-switched Nd∶YAG/Cr4+∶YAG microchip laser, and the seed laser with pulse energy of 82 mJ and pulse width of 1ns is obtained when the repetition frequency is 1 kHz. In the amplA master oscillator power amplifier (MOPA) structure based on Nd∶YAG microchip and Nd∶YVO4 slab is reported. The master oscillator is a passive Q-switched Nd∶YAG/Cr4+∶YAG microchip laser, and the seed laser with pulse energy of 82 mJ and pulse width of 1ns is obtained when the repetition frequency is 1 kHz. In the amplifier, an output pulse energy of 2.3 mJ with peak powers reaching 2 MW and pulse width of 1ns is obtained while the oscillator provides the amplifier with a 82 mJ input. Meanwhile, the M2 factor of beam quality is measured to be 2.48 at x direction and 1.24 at y direction. This laser systerm is compact and air-cooled, the fluctuation of output energy is below 4% when the temperature ranges from 15 ℃ to 32 ℃..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 902005 (2015)
Principle and Progress of Cold Atom Clock in Space
Qu Qiuzhi, Wang Bin, Lü Desheng, Li Tang, Li Lin, Zhao Jianbo, and Liu Liang
The design of a cold atom clock in space (CACS) and its recent progress are described. The CACS is a high precision cold Rubidium atom clock for the application in microgravity environment, which has four parts, including physics, laser source, microwave source, and control system. The first CACS clock science run has The design of a cold atom clock in space (CACS) and its recent progress are described. The CACS is a high precision cold Rubidium atom clock for the application in microgravity environment, which has four parts, including physics, laser source, microwave source, and control system. The first CACS clock science run has been achieved as described. The essential operations of a space cold atom rubidium clock have been demonstrated in the prototype system. The key results of a clock including the ultrahigh vacuum degree, the atomic temperature， and the linewidth of the Ramsey fringes, satisfy the demands of a space cold atom clock. Based on this prototype, an engineering model for space application has been under development..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 902006 (2015)
Study on Dynamic Characteristics of the Passively Q-Swithced Intracavity Optical Parametric Oscillators
Miao Jieguang, Zhao Yanyan, Xu Zhijing, and Yao Yilei
Based on the rate equations for passively Q-switched four-level lasers, and by introducing the concept of optical parametric oscillator (OPO) effective conversion cross-section, a model for the passively Q-switched single resonant intracavity optical parametric oscillator (IOPO) is built. The parametric gain expressionBased on the rate equations for passively Q-switched four-level lasers, and by introducing the concept of optical parametric oscillator (OPO) effective conversion cross-section, a model for the passively Q-switched single resonant intracavity optical parametric oscillator (IOPO) is built. The parametric gain expression which taking account of the absorption loss of the material, walk- off effect, mode matching, etc., and also the OPO effective conversion cross- section expression are deduced. By using the Runge- Kutta method, the dynamic characteristics of the IOPO are simulated. Moreover, the buildup process of the signal pulse is discussed, and the impacts of the signal reflectivity on the energy conversion process and on the buildup time and pulse duration of the signal pulses are analyzed. The simulation results reveal that there is an optimal value for the signal reflectivity which is 0.85. Besides, the simulation results and experimental results are compared, and they match very well. The findings provide a theoretical basis for understanding the performance mechanism and optimization of the passively Q-switched single resonant IOPO..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 902007 (2015)
Optimum of Micro-motor Rotation Realization by Polarized Beam Interaction with Birefringence Particles
Shen Junfeng, Zhu Yanying, Wei Yong, Wang Suoming, and Wang Mingli
Technology of laser driven micro-nano devices provides a new way for driving micro gear in the field of micro mechanical. The polarization induced rotation can be achieved by the transfer of spin angular momentum of polarized light to birefringent particle. Main factors influencing the rotating angular velocity of uniaTechnology of laser driven micro-nano devices provides a new way for driving micro gear in the field of micro mechanical. The polarization induced rotation can be achieved by the transfer of spin angular momentum of polarized light to birefringent particle. Main factors influencing the rotating angular velocity of uniaxial crystal particles are considered, (such as: thickness and radius of the particle, angle between optical axis and crystal plane, reflection of light beam on the crystal plane, phase contrast between the ordinary and extraordinary rays, laser power). The general formula of rotating angular velocity is derived based on the theory of wave optics. The precise manipulation and rotation of calcium carbonate particles is achieved by optical tweezers. By comparing numerical simulation with experimental analysis, results show that experimental results are smaller compared with theoretical data, which is caused by the smaller effective power of laser beam than the measured. The angular velocity of calcium carbonate particles is proportional to laser power, and inversely proportional to the cube of particle radius, moreover, a periodic variation with thickness. According to the test results and theoretical analysis, the parameters of mechanical microrotor are optimized design to improve the rotation frequency. The design results show that calcium carbonate particles chosen as mechanical rotor is more appropriate, furthermore, the radius and thickness of crystal particles should be chosen from 1 micrometer to 3 micrometer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 902008 (2015)
Research on Adaptive Polarization Conversion of Non-Polarization Maintaining Fiber Amplifier
Dong Suhui, Wang Xiaolin, Su Rongtao, Ma Pengfei, Zhou Pu, and Yang Lijia
An adaptive polarization conversion system of non-polarization maintaining (PM) fiber amplifier is reported, which can convert any non- PM laser into linear polarized one. The model of adaptive polarization conversion system is established based on the principle of the controller and the mechanism of polarization evoluAn adaptive polarization conversion system of non-polarization maintaining (PM) fiber amplifier is reported, which can convert any non- PM laser into linear polarized one. The model of adaptive polarization conversion system is established based on the principle of the controller and the mechanism of polarization evolution. The relationship of the output polarization extinction ratio at different conditions is analyzed. On the basis of the optimization results, the system achieves the polarization conversion of non-PM fiber amplifier with the output extinction ratio of 16.7 dB using adaptive polarization conversion technology to control the polarized component directly based on stochastic parallel gradient descent (SPGD) optimization algorithm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 902009 (2015)
Study on A High-Precision Digital Temperature-Control System for All-Solid-State Single-Frequency Green Laser
Jin Xiaoli, Su Jing, Jin Pixian, Wang Wenzhe, and Peng Kunchi
A high-precision digital temperature-control system (HPDTCS) based on TMS320F28069 for all-solidstate single-frequency green laser is designed and built. The speed-change integral PID control algorithm and the high-resolution pulse width modulation (HRPWM) technology are utilized in this system to control the drive curA high-precision digital temperature-control system (HPDTCS) based on TMS320F28069 for all-solidstate single-frequency green laser is designed and built. The speed-change integral PID control algorithm and the high-resolution pulse width modulation (HRPWM) technology are utilized in this system to control the drive current of the thermoelectric cooler (TEC). Depending on the difference of the temperature efficient of the thermistor under higher and lower temperature, the different temperature detection circuits are applied. The HPDTCS consists of three lower (10 ℃ to 40 ℃ ) and a higher (120 ℃ to 160 ℃ ) temperature- control modules with precisions of ± 0.0045 ℃ and ±0.005 ℃, respectively. Applying the HPDTCS to control an all-solid-state single-frequency green laser, the power fluctuation of ±0.33% is achieved at the output power of 11.07 W..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 902010 (2015)
Backscattered Light Diagnostic Technique Based on Shen Guang-III Laser Facility
Wang Feng, Peng Xiaoshi, Yan Yadong, Xu Tao, Wei Huiyue, Li Yulong, and Li Nan
The backscattered light diagnostic technique has been developed on Shen Guang-III laser facility. After using three improvements, the backscattered light can be measured quantitatively. With the rectangle hole, the dispersion effect caused by the wedge lens can be removed. With the full aperture light and white light, The backscattered light diagnostic technique has been developed on Shen Guang-III laser facility. After using three improvements, the backscattered light can be measured quantitatively. With the rectangle hole, the dispersion effect caused by the wedge lens can be removed. With the full aperture light and white light, the transmission of the backscattered diagnostic system can be obtained. After optimizing the diagnostic system, the spectrum and time process of stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) can be achieved. From the experimental data, the backscattered light diagnostic technique on Shen Guang-III laser facility has the primary ability to investigate the effect of laser and plasma interaction (LPI) and laser smooth technique..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 902011 (2015)
Effect of BN Content on Microstructure Evolution and Wear Property of in situ Ti/(TiB+TiN) Hybrid Composite Coating by Laser Cladding
Li Min, Huang Jian, Zhu Yanyan, Li Zhuguo, and Wu Yixiong
TiN-TiB/Ti based composite coating is prepared on Ti-3Al-2V by laser cladding using different molar ratios of Ti and BN, the molar ratios of Ti to BN are 16:1, 8∶1 and 4∶1, respectively. The coating is evaluated and characterized by means of X- ray diffraction (XRD), scanning electron microscope (SEM), electron probe mTiN-TiB/Ti based composite coating is prepared on Ti-3Al-2V by laser cladding using different molar ratios of Ti and BN, the molar ratios of Ti to BN are 16:1, 8∶1 and 4∶1, respectively. The coating is evaluated and characterized by means of X- ray diffraction (XRD), scanning electron microscope (SEM), electron probe microanalyzer (EPMA) and transmission electron microscope (TEM), micro- hardness tester and wear testing machine. The results reveal that: 1) B content has great effect on the microstructure and distribution of phase TiB; 2) TiB nucleates and grows when solubility of B is satisfied to form TiB. Besides, TiB tends to grow on the surface of TiN or grain boundary; 3) with increased BN content, the microhardness and friction performance is improved. The maximal hardness is about 5 times of the substrate. The wear depth is less than half of that of the substrate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 903001 (2015)
Experimental Research of Warm Laser Shock Forming of AZ31 Magnesium Alloy
Zhang Qinglai, Wu Tiedan, Zhang Bingxin, Li Xingcheng, and Shao Wei
In order to study the effects of laser shock with ultra-high strain rate on the warm forming properties of magnesium alloy, experimental research and simulation analysis of laser shock forming (LSF) and warm laser shock forming (WLSF) at 200 ℃ are carried out on AZ31 alloy sheets with Nd: glass laser with power densityIn order to study the effects of laser shock with ultra-high strain rate on the warm forming properties of magnesium alloy, experimental research and simulation analysis of laser shock forming (LSF) and warm laser shock forming (WLSF) at 200 ℃ are carried out on AZ31 alloy sheets with Nd: glass laser with power density of 1.53 GW/cm2 and pulse width of 20 ns. The results show that AZ31 alloy sheets have good WLSF ability with ultrahigh strain rate and can achieve double effsect of warm forming and modification. High value residual compressive stress and high density dislocations are generated on the surfaces of the samples. Residual compressive stress induced by WLSF is more stable than that induced by LSF. The laser shock with the ultra-high strain rate and dynamic recrystallization may contribute to the formation of nano-grains. Surface morphology and roughness and surface residual stress distribution of LSF and WLSF samples are also analyzed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 903002 (2015)
Preparation of PTFE、FEP、PFA Coating by Laser Irradiation
Cui Bing, Ji Lingfei, Yan Yinzhou, Jiang Yijian, and Gao Yu
Baking oven sintering technology is the traditional method to prepare polytetrafluoroethylene (PTFE), fluoroethylenepropylene (FEP) and polyfluoroalkoxy (PFA) coating. In order to solve the drawbacks of the traditional technique, a new preparation method by laser sintering is presented in this paper in which the PTFE、 Baking oven sintering technology is the traditional method to prepare polytetrafluoroethylene (PTFE), fluoroethylenepropylene (FEP) and polyfluoroalkoxy (PFA) coating. In order to solve the drawbacks of the traditional technique, a new preparation method by laser sintering is presented in this paper in which the PTFE、 FEP and PFA coating are prepared by 1070 nm continuous fiber laser irradiation replacing traditional hightemperature baking oven curing process. Meanwhile, by controlling laser scanning path, the preparation of the graphical PTFE、FEP、PFA coatings is achieved. The optimized processing parameters are obtained. Analysis indicates that the preparation mechanism is based on the thermal effects of laser energy input, which induces the original powder sprayed layer turn into molten state then promotes the crosslinking curing for the formation of the coating. The whole process acts as physical change without any changes of chemical composition of the material..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 903003 (2015)
Irregular Mill Roll Fiber Laser Texturing Method Based on Random Frequency and Random Power
Yan Ran, Zhang Lichao, Zhang Yisheng, and Zhao Zuye
The mill roll laser texturing is the newest mill roll texturing method which has broad application prospects. As the limit of processing method, the distribution of the craters on the surface of the mill roll is anisotropy and periodicity, which makes the surface of the texturing cold-roll steel not satisfy the needs. The mill roll laser texturing is the newest mill roll texturing method which has broad application prospects. As the limit of processing method, the distribution of the craters on the surface of the mill roll is anisotropy and periodicity, which makes the surface of the texturing cold-roll steel not satisfy the needs. A fiber laser control method is proprsed to produce random frequency and power lasers. This method can control the fiber laser device output particular wave form laser by the pulse width modulation signal which is calculated by a pseudorandom algorithm. The surface of the mill roll produced by this method is isotropic and irregular which can reach the quality requirements. In addition, it can also improve production efficiency. The laser texturing equipment based on this method is applied in practice and makes well effect..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 903004 (2015)
Numerical Simulation of Temperature Field and Stress Distribution in Inconel718 Ni Base Alloy Induced by Laser Cladding
Dai Deping, Jiang Xiaohua, Cai Jianpeng, Lu Fenggui, Chen Yuan, Li Zhuguo, and Deng Dean
Based on Abaqus code, a nonlinear finite element method is developed to simulate temperature field and stress distribution in 718 alloy induced by laser cladding. According to the characteristics of laser cladding, a moving heat source model is established through developing a user subroutines in Abaqus code. TemperatuBased on Abaqus code, a nonlinear finite element method is developed to simulate temperature field and stress distribution in 718 alloy induced by laser cladding. According to the characteristics of laser cladding, a moving heat source model is established through developing a user subroutines in Abaqus code. Temperature and residual stress fields in single-channel monolayer cladding, single-channel double layers cladding and singlechannel ten layers cladding are calculated using the developed computational approach. The features of temperature field and the formation of stress are investigated numerically. The results obtained from this research are helpful in deeply understanding mechanism of metallurgical defects such as hot cracking and are also beneficial for finding measures to prevent the occurrence of these defects..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 903005 (2015)
Fatigue Life Evaluation for Laser Cladding Component Based on Non-Linear Continuum Fatigue Damage Model
Hua Liang, Tian Wei, Liao Wenhe, and Zeng Chao
Chaboche′s model of nonlinear continuum fatigue damage is modified based on the impact of crack closure and residual tension stress of laser cladding effect on fatigue damage. A cumulative fatigue damage model is developed accordingly to predict the fatigue life for laser cladding component. The related parameters are Chaboche′s model of nonlinear continuum fatigue damage is modified based on the impact of crack closure and residual tension stress of laser cladding effect on fatigue damage. A cumulative fatigue damage model is developed accordingly to predict the fatigue life for laser cladding component. The related parameters are concluded from fully reversed fatigue experiment and static tension test and residual tension stress test. To verify the proposed model, tension-compression fatigue tests under two stage loadings (high-low loading and low-high loading) are carried out. The results show that the calculated value and experimental value are in good agreement. It has been proved to be an efficient method to predict the fatigue life of the laser cladding component..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 903006 (2015)
Study on Deformation Behavior in Selective Laser Melting Based on the Analysis of the Melt Pool Data
Zhang Kai, Liu Tingting, Zhang Changdong, and Liao Wenhe
Deformation resulting from residual stresses is a key problem in selective laser melting (SLM). The different melting pool conditions between the deformation and normal specimens are compared based on data collected by the melt pool monitoring system. Furthermore, the forming mechanism and deformation process of the spDeformation resulting from residual stresses is a key problem in selective laser melting (SLM). The different melting pool conditions between the deformation and normal specimens are compared based on data collected by the melt pool monitoring system. Furthermore, the forming mechanism and deformation process of the specimens is investigated. Results from the experiments suggest that deformation of the specimens occurs in the initial stage of the process. The melt pool area decreases and the intensity of the melt pool increases. The experiments indicate that it is possible to detect deformation of the specimens by monitoring the melt pool behavior..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 903007 (2015)
Study of Narrow Gap Laser-Metal Insert Gas Hybrid Welding GH909 Alloy
Liu Ting, Yan Fei, Liu Sang, Wang Chunming, and Hu Xiyuan
The influence of welding parameters on weld appearance is investigated by experiment in narrow gap laser metal insert gas (MIG) hybrid welding 10 mm low thermal expansion superalloy GH909. The results show that a desirable weld can be obtained by employing a groove of 10° and the root face of 0.7 mm. A faster weldThe influence of welding parameters on weld appearance is investigated by experiment in narrow gap laser metal insert gas (MIG) hybrid welding 10 mm low thermal expansion superalloy GH909. The results show that a desirable weld can be obtained by employing a groove of 10° and the root face of 0.7 mm. A faster welding speed would result in a narrower weld width. The defocus plays an important role in the two heat source coupling mechanism and the better parameter to realize laser-arc synergetic effect is 1 mm in experimental conditions. An appropriate increase in welding gap can improve the penetration. A desirable weld profile without any obvious defects can be obtained using optimized welding parameters. Grains adjacent to the heat affected zone (HAZ) are perpendicular to the fusion line. The columnar crystals touch and restrain each other to form a herringbone in the weld center..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 903008 (2015)
Numerical Simulation of Dynamic Response of Round Rod Subjected to Laser Shocking
Zhang Xingquan, Zhang Yan, Duan Shiwei, Huang Zhilai, Feng Jianyou, and Wang Biao
The dynamic response of 2024 aluminum alloy round rod subjected to laser shocking is investigated by ABAQUS numerical simulation software. The attenuation characteristics of stress waves propagating along longitudinal and transverse direction as a function of propagating distance are systematically investigated and theThe dynamic response of 2024 aluminum alloy round rod subjected to laser shocking is investigated by ABAQUS numerical simulation software. The attenuation characteristics of stress waves propagating along longitudinal and transverse direction as a function of propagating distance are systematically investigated and the effects of rod diameters on the attenuation of the peak of stress waves with propagating distance are also discussed. The effects of rod diameters on residual stress field are analyzed. The results indicate that the peak values of stress waves along longitudinal and transverse direction gradually decrease with increasing propagating distance, and the phenomenon of wave diffusion appears with stress wave propagation. The peak values of the stress waves attenuate fast first and then slow. With the diameter of round rod increasing, the residual stress field in the rod becomes more uniform and regular, and the depth of residual compressive stress increases and gradually reaches saturation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 903009 (2015)
Research of Microstructure and Mechanical Properties of Laser Tailor-Welded Blank of Cold Rolled Multi-Phase Steel and HSLA
Zhang Fan, Li Fang, Hua Xueming, Wang Shien, Chu Weidong, and Wang Daming
To research the tailor welding of cold rolled multi-phase steel and high strength low alloy (HSLA), tailor welding is conducted with 10 kW fiber laser varying laser power, welding velocity and defocusing amount. Weld seam formation, metallographic microstructure, hardness and formability are tested. The results show thTo research the tailor welding of cold rolled multi-phase steel and high strength low alloy (HSLA), tailor welding is conducted with 10 kW fiber laser varying laser power, welding velocity and defocusing amount. Weld seam formation, metallographic microstructure, hardness and formability are tested. The results show that the formation of weld seam is sound. The metallographic microstructure of weld seam is mainly lath martensite dendrites. Heat affected zone of multi-phase steel is combined with tempered softening zone, fine grain equiaxed zone, coarse grain equiaxed zone and the mixture zone. The width of softening zone is affected by welding velocity most severely. The tensile strength and formability of weld seam are sound. The fracture location of tensile specimen is base metal of HSLA consistently. The fracture location of Erickson LDH test is parallel with the weld seam on the side of HSLA. The results can provide guidance on welding processing and theory of tailor welding of multigauge cold rolled multi-phase steel and HSLA..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 903010 (2015)
Design and Implementation of an Off-Axis Rotary Optical Fiber Transmission System
Liu Fei, Li Yi, Hao Rulong, Sun Yao, Tang Jiayin, Chen Peizu, Jiang Wei, Wu Zhengyi, Xu Tingting, Fang Baoying, Wang Xiaohua, and Xiao Han
A new-type off-axis rotary optical fiber transmission system is designed to achieve the connection of the optical signals under the rotary state. The collimating and expanding effect of the fiber collimator with large aperture is analyzed based on the propagation theory of Gaussian beam, and the structure and output beA new-type off-axis rotary optical fiber transmission system is designed to achieve the connection of the optical signals under the rotary state. The collimating and expanding effect of the fiber collimator with large aperture is analyzed based on the propagation theory of Gaussian beam, and the structure and output beam properties of the fiber collimator is optimized by ZEMAX. The relative optical characteristics of the transmission system are measured. The results show that the fiber collimator outputs Gaussian beam at a working distance of 50 mm. Beam waist radius and far- field divergence degree are 18 mm and 5.48 × 10- 2 mrad, respectively. The maximum connection loss of the transmission system is 23.28 dB when the signal transmission rate is 1.25 Gb/s and the rotation speed is 80 r/min. The overall performance of the transmission system satisfies the requirement of stability for high-speed optical signal transmission between the rotary parts..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 905001 (2015)
Feedback Control System of Electro-Optic Modulator Used for Transferring One Pulse per Second
Cheng Nan, Chen Wei, Liu Qin, Xu Dan, Yang Fei, Gui Youzhen, and Cai Haiwen
A bias point feedback control system of Mach-Zehnder modulator (MZM) for transferring one pulse per second (1PPS) is used in time and frequency transfer via optical fiber. The low-level voltage of the 1PPS output by photodiode is used to measure the drift of the bias point, which is set between minimum point (Null) andA bias point feedback control system of Mach-Zehnder modulator (MZM) for transferring one pulse per second (1PPS) is used in time and frequency transfer via optical fiber. The low-level voltage of the 1PPS output by photodiode is used to measure the drift of the bias point, which is set between minimum point (Null) and orthogonal point of positive slope (Quad+) on transmission curve. The measured signal is digitally processed and used to control the feedback system to stabilize the bias point. The theoretical derivation of the principle is described and the performance of the system is compared with that of commercial bias point stabilized system based on dither method. The experimental results show that the behavior of our system is better, and the instability results from the dither can be avoided. The peak-peak fluctuated value of the propagation delay of the 1PPS is 174 ps, and the root-mean-square (RMS) value is 18 ps. The time deviation (TDEV) of the 1PPS for the averaging time of 104 s decreases to 1.7 ps..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 905002 (2015)
Investigation of Four-Wave Mixing in Microstructure Fiber with Cladding Composed of Three Large Air-Holes
Bi Xinying, Wang Wei, Yang Jianju, Han Ying, Zhou Guiyao, Qi Yuefeng, and Hou Lantian
Microstructure fiber whose cladding is composed of three air-holes is designed. Its mode characteristics are investigated by full vector finite element method. Because of C3v symmetry, the fiber contains 4 distinct classes of mode and the fundamental mode is degenerate mode. The dispersion and phase mismatch in fundameMicrostructure fiber whose cladding is composed of three air-holes is designed. Its mode characteristics are investigated by full vector finite element method. Because of C3v symmetry, the fiber contains 4 distinct classes of mode and the fundamental mode is degenerate mode. The dispersion and phase mismatch in fundamental mode of the fiber is analyzed when d/Λ=0.986，d changes from 10 μm to 16 μm and d=14 μm，d/Λ changes from 0.946 to 0.986. It is found that with fixed pump, changes on fiber structure parameters have great influence on the position of Stokes signal while the position of anti-Stokes signal stays almost unchanged. Four-wave mixing and frequency conversion experiments are carried out in the outer cladding of a homemade double cladding microstructure fiber. Stokes and anti-Stokes signals at 1859 nm and 551 nm are observed respectively when pumping fs pulse with central wavelength at 850 nm. The experimental result agrees well with the theoretical prediction on the anti-Stokes signal wavelength with only 3 nm divergence. The ratio of anti-Stokes signal power to the residual pump power is as high as 73..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 905003 (2015)
Mach-Zehnder Modulator Bias Controller for Large Modulation Signal
Zhou Pengwei, Li Ting′an, Guo Yunfeng, Sun Zhiqiang, and Zhuang Zhuo
The operating characteristic of Mach-Zehnder modulator is influenced severely by environmental factors such as temperature changing. Therefore, a bias controller is required to stabilize the operating point automatically. Applying a dither signal and detecting its harmonic wave to measure the position of operating poinThe operating characteristic of Mach-Zehnder modulator is influenced severely by environmental factors such as temperature changing. Therefore, a bias controller is required to stabilize the operating point automatically. Applying a dither signal and detecting its harmonic wave to measure the position of operating point is a useful method. However, when the amplitude of modulation signal is large, the prior art method fails to lock the bias point. The harmonic wave resulting from modulation transfer function has been simulated and analyzed. It is shown that previous harmonic wave calculation formulate will not be suitable when a large modulation signal inputs. Therefore, we have modified the calculation method and proposed a bias controller with new architecture to maintain the working point in large modulation signal condition. At last, we have developed corresponding circuit, and test result shows that our method can lock the working point within accuracy of 1°, which is quite useful in large modulation signal application..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 905004 (2015)
Research on the Bending Sensing Characteristics of PM-PCF Based on Intermodal Interference
Liu Feng, Feng Xiaolong, Guo Xuan, and Xu Xiang
A novel bending sensing scheme based on intermodal interference of dual-hole polarization maintaining photonic crystal fiber (PM-PCF) is presented. The finite difference beam propagation method is used to analyze the bending characteristics of dual-hole PM-PCF. The relationship between normalized interference output inA novel bending sensing scheme based on intermodal interference of dual-hole polarization maintaining photonic crystal fiber (PM-PCF) is presented. The finite difference beam propagation method is used to analyze the bending characteristics of dual-hole PM-PCF. The relationship between normalized interference output intensity of two low order polarization modes and bending radius is calculated thoroughly when the dual-hole PMPCF is modulated by bending. Further, the wavelength influence of bending sensing characteristics is discussed theoretically. And an experiment system is set up to verify the feasibility of bending sensing based on intermodal interference in dual-hole PM-PCF. The experimental results show that the bending sensor designed in this paper has excellent linearity and accuracy when the bending radius ranges from 10 mm to 30 mm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 905005 (2015)
Design of Optimization-Baffle for GEO Laser Communication
Li Xiaoming, Zhang Lizhong, Han Cheng, Liu Weida, Yang Xianwei, and Jiang Huilin
The optical antenna of geosynchronous earth orbit (GEO) laser communication system exposes outside of satellite. Solar radiation affects the optical system seriously, and reduces available probability.The effect is more serious when the sun directly shine the primary mirror. The baffle can reduce the effect, but it is The optical antenna of geosynchronous earth orbit (GEO) laser communication system exposes outside of satellite. Solar radiation affects the optical system seriously, and reduces available probability.The effect is more serious when the sun directly shine the primary mirror. The baffle can reduce the effect, but it is limited by the fairing′s size of rocket. By researching the characteristics of the GEO laser communication and analyzing the situation of primary mirror shined by the sun, a modified baffle with internal grids is designed to reduce the effect of the sun. Then the optical-device′s temperature and the available probability of the system combined the thermal control design are analysed. The results show that the available probability is improved from 93% with traditional baffle to 99.5% with the improved baffle. The GEO laser communication system can almost work all day with the modified baffle..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 905006 (2015)
Formation Principle of Ring Laser Beam and Research on Laser Welding of Polymer Materials
Xu Guojian, Tian Xiyu, Hang Zhengxiang, Ma Mingzhang, Li Hongli, and Liu Xiangyu
A ring beam optics is developed for a circular seam welding of the automotive using a fiber laser, and the polymer material with a circular seam are firmly welded in a super-short time. As the results, with increase of focal length of collimating lens, the outside diameter of the ring laser beam is hardly changed; the A ring beam optics is developed for a circular seam welding of the automotive using a fiber laser, and the polymer material with a circular seam are firmly welded in a super-short time. As the results, with increase of focal length of collimating lens, the outside diameter of the ring laser beam is hardly changed; the inside diameter of the ring laser beam decreases; the width of the ring laser beam is increased in the experiment. Distance (L12) between the first axi-cone lens and the second axi-cone lens increases, the outside diameter and inside diameter as the ring laser beam increases simultaneously, and the width of the ring laser beam is almost fixed. Moreover, it is confirmed that the intensity distribution of the ring beam becomes uniform by adjusting the coaxial performance of collimating lens, the first axi-cone lens and the second axi-cone lens. The ring laser beam has been outside diameter of 54 mm, inside diameter of 47 mm, and width of 3.5 mm, performing the high speed welding of lap joints in the (2+1) mm thickness of polymer material. When pressure is 100 N, laser power is 800 W and irradiation time is 0.6 s, the tensile-shear strength of the polymer material joint with laser welding is approaching to the base metal, whose fracture of the stretching pieces is appeared in the base mental (TPV-elastomer)..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 906001 (2015)
Studies on the Phase Explosion of Laser Dressing Bronze-Bond Diamond Grinding Wheel by a Pulsed Fiber Laser
Cai Song, Chen Genyu, and He Jie
The existence of a phase explosion phenomenon during the process of grinding wheel laser dressing is proposed, and the negative effects of a phase explosion on laser dressing are analyzed. Additionally, a theoretical study on phase explosion is conducted. In the experiment, the processing parameters of the laser duringThe existence of a phase explosion phenomenon during the process of grinding wheel laser dressing is proposed, and the negative effects of a phase explosion on laser dressing are analyzed. Additionally, a theoretical study on phase explosion is conducted. In the experiment, the processing parameters of the laser during phase explosion are studied. A high-speed camera is used to observe phase explosion in the laser dressing process. An ultra-depth three-dimensional microscope system is used to observe the topography of the bronze bond diamond grinding wheel after dressing as well as the bronze wheel surface quality. It is concluded that to avoid phase explosion from occurring in the laser dressing of the bronze bond grinding wheel, chip space around the bond must exist for the abrasive particle protrusions. The processing parameters of laser dressing under certain condition are optimized, and the desired dressing effect is achieved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 906002 (2015)
Friction and Wear Properties of AZ31 Magnesium Alloy by Laser Shock Processing
He Huanju, Zhang Lingfeng, Yang Genmei, and Lü Yangyang
AZ31 magnesium alloy is treated by laser shock processing (LSP) using high-energy pulse laser beams. The dry-sliding wear tests of untreated and treated samples by LSP are conducted on the UMT-2 sliding wear tester. LSP can improve the wear resistance of AZ31 magnesium alloy through analyzing the micrographs of samplesAZ31 magnesium alloy is treated by laser shock processing (LSP) using high-energy pulse laser beams. The dry-sliding wear tests of untreated and treated samples by LSP are conducted on the UMT-2 sliding wear tester. LSP can improve the wear resistance of AZ31 magnesium alloy through analyzing the micrographs of samples′ worn surfaces and worn debris and energy dispersive spectra of worn debris. Under the same conditions, friction coefficients and mass loss of AZ31 magnesium alloy treated by LSP are both significantly lower than untreated samples and the debris are even finer, which indicates that LSP can improve the wear resistance of AZ31 magnesium alloy. Besides, the friction mechanism of AZ31 magnesium alloy treated by LSP turns from delaminate wear into abrasive wear..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 906003 (2015)
Mechanical Properties of Microweld of Silica Glass to Silicon by Femtosecond Laser
Cheng Zhan, Guo Wei, Liu Lei, Zou Guisheng, and Zhou Yunhong
Femtosecond laser has distinct advantages in the field of micro/nano joining because of its unique properties, such as low heat input, nonlinear absorption and almost no heat affected zone. Silica glass and silicon are welded using 800 nm femtosecond laser with power of 4~30 mW and frequency of 1 kHz. The shear strengtFemtosecond laser has distinct advantages in the field of micro/nano joining because of its unique properties, such as low heat input, nonlinear absorption and almost no heat affected zone. Silica glass and silicon are welded using 800 nm femtosecond laser with power of 4~30 mW and frequency of 1 kHz. The shear strength and failure modes of the joints are investigated, the joint cross sections processed by etching are observed, and the fracture surface is also studied. The shear strength of the joints is in a range of 7~54 MPa, depending on the welding parameters. It is found that the laser power, scanning speed, numerical aperture and defocusing length have significant effect on the joint strength. The results indicate that focusing the laser on the interface can obtain high shear strength joints with appropriate laser power and scanning speed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 906004 (2015)
Study on Tribological Properties of Ni-Based Silicide Coating on Copper by Laser Cladding
Liu Xiaopeng, Zhang Peilei, Lu Yunlong, Yan Hua, and Yu Zhishui
Two Ni-Cr-Si coatings of Cr3Si+gNi (45Ni-26Cr-29Si) and Ni16Cr6Si7+Ni2Si (60Ni-10Cr-30Si) (atomic fraction, %) are synthesized on pure copper using laser cladding. The microstructures of the coatings are analyzed by optical microscope (OM), scanning electron microscope (SEM), X - ray diffraction (XRD) and energy disperTwo Ni-Cr-Si coatings of Cr3Si+gNi (45Ni-26Cr-29Si) and Ni16Cr6Si7+Ni2Si (60Ni-10Cr-30Si) (atomic fraction, %) are synthesized on pure copper using laser cladding. The microstructures of the coatings are analyzed by optical microscope (OM), scanning electron microscope (SEM), X - ray diffraction (XRD) and energy dispersive spectrometer (EDS). The wear resistance of the coatings is evaluated under ambient temperature. The results show that due to the different crystallization temperature ranges between binary phase and ternary phase, constitutional supercooling degrees are different in the process of crystallization and different microstructures are formed. The coating consisted of Cr3Si+gNi has an average hardness of 1000 HV and the friction coefficient of 0.5, but 4 cracks appear to the corner of indentation when loads add to 500 g. The coating consisted of Ni16Cr6Si7+Ni2Si with an average hardness of 900 HV, fine toughness of no cracks generating under loads of 1000 g, an average friction coefficient of 0.5 has good comprehensive performance than that of the coating consisted of Cr3Si+gNi..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 906005 (2015)
Short-Time Hydrolization and XPS Characterization for Nd-Doped Phosphate Laser Glass
Li Meng, Xu Yongchun, Wang Congjuan, Chen Wei, and Hu Lili
The varation of main element contents in pure water is measured and analyzed during a short-time hydrolization of Nd-doped phosphate laser glass. To characterize the glass surface structure, X-ray photoelectron spectroscopy (XPS) is used before and after the hydrolization. As the major network former, P5+ shows a similThe varation of main element contents in pure water is measured and analyzed during a short-time hydrolization of Nd-doped phosphate laser glass. To characterize the glass surface structure, X-ray photoelectron spectroscopy (XPS) is used before and after the hydrolization. As the major network former, P5+ shows a similar hydrolization behavior like network modifiers of Li+ , K + , Ba2 + . Their dissolution rates are in the same order of magnitude and their ion concentrations gradually saturate during this short-time hydrolization, in agreement with the typical hydrolization behavior for most of phosphate glasses. Especially for Al in the glass sheets and glass powders, probably as network former and/or modifier, its content in the water shows a non-monotonic relation with hydrolization time. According to XPS analysis for Al2p binding energy, Al acts as both network former and network modifier in our Nd-doped phosphate laser glass. Before hydrolization, more Al acts as network former. During the hydrolization process, more Al acts as network modifier. Such a structure characterization may account for its non-monotonic hydrolization behavior, as well as the reason that the water durability can be enhanced by adding Al2O3 into phosphate laser glass..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 906006 (2015)
Effects of Least Spatial Period on the Fabrication and Performance of Continuous Phase Plate
Wen Shenglin, Tang Caixue, Zhang Yuanhang, Yan Hao, Hou Jing, and Luo Zijian
Least spatial period is an important parameter for the design and fabrication of continuous phase plate (CPP). Based on the requirement of laser facility for inertial confinement fusion, a method of design and analysis for CPP with different least spatial periods is built up. The effects of least spatial period on the Least spatial period is an important parameter for the design and fabrication of continuous phase plate (CPP). Based on the requirement of laser facility for inertial confinement fusion, a method of design and analysis for CPP with different least spatial periods is built up. The effects of least spatial period on the fabrication and performance of continuous phase plate have been studied. The results show that the removal function size is linearly correlated to the least spatial period, and the relationship between the removal and the square root of least spatial period is about linear, so the fabrication with larger least spatial period should be easier because the CPP has more medium-high frequency, but it has more material to be removed. Moreover, the beam shaping performance of CPP is rarely influenced by the least spatial period, the difference of capacity usage ratio caused by different CPP is smaller than 0.2%. But the uniformity of top focal spot caused by CPP becomes more excellent when the least spatial period is minimized, the nonuniformity of least spatial period CCP of 5 mm is 3.5% less than that of 15 mm. So the selected least spatial period should be minimized, while it can’t exceed the ability of the fabricating equipment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 908001 (2015)
High-Resolution Imaging by Bi-Linear CCD Shifting Sampling
Xu Shaoxiong, Chen Changzheng, Sun Bin, Zhang Xingxiang, and Ren Jianyue
The resolution of remote sensing camera is restricted by the charge coupled device (CCD) pixel size. To solve the problem, imaging capability of optical system in frequency bandwidth exceeding Nyquist frequency is used to develop a camera which consists of two linear CCDs. These two CCDs are stitched together with a haThe resolution of remote sensing camera is restricted by the charge coupled device (CCD) pixel size. To solve the problem, imaging capability of optical system in frequency bandwidth exceeding Nyquist frequency is used to develop a camera which consists of two linear CCDs. These two CCDs are stitched together with a halfpixel width displacement in both directions along and perpendicular to the CCD axis. The principle of improving the resolution of the proposed system is presented. In hipermode, one way interpolation algorithm based on integrated gradients to determine the direction of interpolation is proposed to avoid zipper effect caused by average method. In supermode, high resolution image is acquired in real time by using random access memory (RAM) blocks inside field programmable gate array (FPGA) to regroup image stagger. Gray mean gradients (GMG) of the two high resolution images are increased by factors of 62.5% and 78.3% respectively after using Wiener filter. Results show that the proposed algorithm can make image edge clear and intact. The effect of the algorithm is better than average method and the hardware implementation is easy. The resolution is 1.16 and 1.6 times greater than that of conventional system . Two imaging method can also reduce the image frequency aliasing. Sampling phase staggered technology can take advantage of imaging capability of optical system in high-frequency bandwidth and perform high-resolution imaging..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 908002 (2015)
Influence of Regularization Matrix on Inversion of Bimodal Dynamic Light Scattering Data
Liu Wei, Wang Yajing, Chen Wengang, Ma Lixiu, and Shen Jin
The inversion of bimodal dynamic light scattering data is very difficult. Tikhonov regularization method is the often used inversion algorithm, however, the influence of different regularization matrices on the inversion is not clear yet. Two bimodal particle size distributions with 6 levels of noise are inverted by usThe inversion of bimodal dynamic light scattering data is very difficult. Tikhonov regularization method is the often used inversion algorithm, however, the influence of different regularization matrices on the inversion is not clear yet. Two bimodal particle size distributions with 6 levels of noise are inverted by using identity matrix L1, first order difference matrix L2 and second order differential matrix L3. Simulation data shows that the bimodal resolution decrease with the increase of noise level. The anti-interference ability of the algorithm is stronger when the components of bimodal distribution are closer. Under the same noise level, the bimodal resolution of matrix L3 is of the best, while the error of inversion is minimum; correspondingly the bimodal resolution of matrix L1 is of the worst, while the error of inversion is maximum. The matrix L3 can distinguish the smallest peak value size ratio, while matrix L1 can only distinguish the biggest peak value size ratio. Under the same noise level, peak value size ratio is bigger and the bimodal resolution is stronger. Therefore, matrix L3 should be used in order to get the correct inversion result by inverting the noisy scattering data. Finally, the inversion of experimental particles confirms this conclusion..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 908003 (2015)
Generalized Phase-Shifting Phase Retrieval Approach Based on Time-Domain Fourier Transform
Zhang Wangping, Lü Xiaoxu, Liu Shengde, Zhao Hui, and Zhong Liyun
An generalized phase-shifting phase retrieval approach based on time-domain Fourier transform (TFT) is proposed. There is no the special requirement for the phase shift calibration, and the measured phase can be retrieved quickly from a sequence of interferograms whose phase shifts are changed monotonously. By using FoAn generalized phase-shifting phase retrieval approach based on time-domain Fourier transform (TFT) is proposed. There is no the special requirement for the phase shift calibration, and the measured phase can be retrieved quickly from a sequence of interferograms whose phase shifts are changed monotonously. By using Fourier transform to obtain the object’s phase point-by-point from the frequency domain, the proposed method not only has good anti-interference performance, but also the fringe number of the interferogram is not required. Even in the case that the fringe number of the interferogram is less than one, the proposed approach still works well. Both the numerical simulation and experimental results show that the proposed approach is simple, convenient, fast and high precision..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 908004 (2015)
Blackbody Source Emissivity Measurement Method Based on Controlling Surroundings Radiation
Song Jian, Hao Xiaopeng, Yuan Zundong, Liu Zenglin, Xu Min, and Ding Lei
The progress of the blackbody source emissivity measurement based on the controlling surrounding radiation is presented, including the principle, method and equipment. The theoretical model is established according to the Planck′s radiation law. The equipment is set up, and the blackbody emissivity results are analyzedThe progress of the blackbody source emissivity measurement based on the controlling surrounding radiation is presented, including the principle, method and equipment. The theoretical model is established according to the Planck′s radiation law. The equipment is set up, and the blackbody emissivity results are analyzed and factors affecting the results are discussed. The measurement results of blackbody emissivity agree well with the theoretical modeling result, and the standard deviation of measurement results achieves 0.07%. It is shown that the temperature repetitiveness of the heated halo has little influence on the emissivity results by the proposed method. Similarly, the change of heated halo temperature has little effect on the results when the difference in temperature between heated halo and blackbody is large enough. The proposed method has potential applications in the blackbody emissivity measurement during the thermal infrared remote sensing facility on orbit. It also set an important base to raise the level of infrared remote sensing calibration on board..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 908005 (2015)
Phase Retrieval with One Interferogram by Reflecting Off-Axis Microscopic Interferometry
Zeng Yanan, Lei Hai, Chang Xinyu, Hu Xiaodong, and Hu Xiaotang
A technique called off-axis microscopic interferometry is developed to measure the surface profile of microstructures. This technique involves the use of a modified Mach-Zehnder microscopic interferometer with a tilted reference wave. The technique uses a CCD camera to record the off-axis microscopic interferogram and A technique called off-axis microscopic interferometry is developed to measure the surface profile of microstructures. This technique involves the use of a modified Mach-Zehnder microscopic interferometer with a tilted reference wave. The technique uses a CCD camera to record the off-axis microscopic interferogram and performs filtering in the Fourier plane via the Fourier transform method for phase retrieval. In contrast to classical microscopic interferometry, the carrier frequency of the off-axis microscopic interferogram is sufficiently high to facilitate acquisition of the phase from only one interferogram. As a result, measurements using this technique are vibration-immune and efficient. The experimental results obtained for a step height standard as well as a microhole array are consistent with measurements taken using a stylus profilometer. Further, the results of a comparative experiment conducted using a Mirau interferometric microscope show that the carrier frequency added to the classical microscopic interferogram cannot be as high as that of off-axis microscopic interferogram. Therefore, it will lead to incorrect phase retrieval with one interferogram..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 908006 (2015)
A Double Encryption Algorithm Research Based on Computer Generated Hologram
Han Chao, Wan Rui, Liu Yang, and Wang Fengsui
To ensure the security issues of information transmission in modern network, a double encryption algorithm of computer generated hologram based on compressed sensing theory and block Arnold transformation scrambling has been proposed. The phase-only hologram of original image has been produced, the hologram has been enTo ensure the security issues of information transmission in modern network, a double encryption algorithm of computer generated hologram based on compressed sensing theory and block Arnold transformation scrambling has been proposed. The phase-only hologram of original image has been produced, the hologram has been encrypted by using the random measurement matrix of compressed sensing as a key. It has been encrypted again by block Arnold transformation scrambling. The image after two-time encryption can be decrypted by using the keys and reproduce the original one. Compare to conventional optical holographic encryption, this method has a more flexible design, simple optical path and the two encryptions both have randomness, so it improves the security of information transmission greatly. Result shows that the decryption image is ideal, safe and robust. The proposed method is verified by building a holographic display system based on silicon liquid crystal spatial light modulator..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 909001 (2015)
Tunable Optical Bottle Beam Generated via Self-bending Airy Beam Arrays
Qian Yixian, and Li Denghui
We theoretically demonstrate a novel optical bottle beam that is produced by exploiting the self-bending characteristic of circularly arranged Airy beam (AB) arrays. The AB arrays propagate with an inward acceleration to generate such an optical bottle beam, whose size can be flexibly controlled by changing the spacingWe theoretically demonstrate a novel optical bottle beam that is produced by exploiting the self-bending characteristic of circularly arranged Airy beam (AB) arrays. The AB arrays propagate with an inward acceleration to generate such an optical bottle beam, whose size can be flexibly controlled by changing the spacing distance between ABs in the input plane. Moreover, the intensity of our proposed optical bottle beam is significantly increased in the output plane by superposing multiple coherent ABs, as compared to the case of the conventional Gaussian beam (GB). Numerical simulations are performed, the results of which show that the tunable optical bottle can be formed by exploiting the self-bending property of ABs. Some possible applications are also discussed. We believe that the intriguing characteristics of the tunable optical bottle can lead to novel techniques in medical treatment and atom manipulation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 909002 (2015)
Three-Dimensional Display Based on Volume Holography
Wang Zheng, Cao Liangcai, Zhang Hao, and Jin Guofan
Holographic three-dimensional (3D) display can present a 3D scene with all characteristics of real-world objects. Large data recording and high resolution reconstruction are the challenges for holographic display. Volume holography is capable of recording and retrieving large capacity data based on 3D Bragg grating forHolographic three-dimensional (3D) display can present a 3D scene with all characteristics of real-world objects. Large data recording and high resolution reconstruction are the challenges for holographic display. Volume holography is capable of recording and retrieving large capacity data based on 3D Bragg grating for high resolution 3D display. 3D display based on volume holography is studied. Full- parallax kinoforms of the 3D objects are acquired by the algorithm of computer generated holography. The wavefront information is encoded by a phaseonly spatial light modulator. Multiple holograms can be imposed into the same holographic element(hogel) in the volume holographic polymer by using angle multiplexing. The 3D object are reconstructed by illuminating with the reference beam. The space-bandwidth product of the system is expanded..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 909003 (2015)
Lithography Alignment Technology Based on Two-Dimensional Ronchi Grating
Si Xinchun, Tong Junmin, Tang Yan, Hu Song, Liu Junbo, Li Jinlong, Zhou Yi, and Deng Qinyuan
A kind of nanometer lithography alignment method for two dimensional (2D) synchronization alignment in proximity lithography is presented. This method is based on the moiré effect. Two superposed 2D gratings with slightly different periods are adopted to generate a set of periodic moiré fringes, the period ofA kind of nanometer lithography alignment method for two dimensional (2D) synchronization alignment in proximity lithography is presented. This method is based on the moiré effect. Two superposed 2D gratings with slightly different periods are adopted to generate a set of periodic moiré fringes, the period of which is hugely magnified with regard to that of two gratings and the relative displacement of gratings is encoded in the phase of fringes. Using the independent spectrum distribution of x and y direction in the Fourier spectrum and parsing the phase information on the transverse and longitudinal of moiré fringe by Fourier transformation can realize two dimensional high precision synchronization alignment. A kind of complex amplitude distribution model about two Ronchi 2D gratings alignment is built. Then, the relationship between the offsets of substrate and mask with moiré fringe is derived on the basic of this model. A simulation analysis about built model using computer is performed. The result shows that the accuracy can reach 2 nm when noise is considered; an experiment is made to test this alignment method after numerical computation. The accuracy of the result can reach 22 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 910001 (2015)
Estimation of Atmospheric Optical Turbulence Profile by WRF Model at Gaomeigu
Qing Chun, Wu Xiaoqing, Li Xuebin, Zhu Wenyue, Rao Ruizhong, and Mei Haiping
When electromagnetic waves propagate through the atmosphere, the turbulence causes phase fluctuations and degrades the image quality of the photoelectric system. Adaptive optics is used to correct the effect of atmospheric turbulence, but in order to optimize system performance, as well as the large telescope sitting, When electromagnetic waves propagate through the atmosphere, the turbulence causes phase fluctuations and degrades the image quality of the photoelectric system. Adaptive optics is used to correct the effect of atmospheric turbulence, but in order to optimize system performance, as well as the large telescope sitting, designing and operating, monitoring optical turbulence intensity and integral parameters of the observing stations are necessary. Measuring atmospheric optical turbulence takes a huge labor, materials and financial resources, and it is difficult to measure a large region continuously. The weather research and forecasting (WRF) model is introduced based on the optical turbulence parameterization, the profiles of the optical turbulence intensity are simulated using turbulence parameterized model. Simulation results are compared with measurements at Gaomeigu observing station, the results show that the simulation profiles emerge the variation tendency of the upper air atmospheric optical turbulence, and basically coincide with the measurements..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 913001 (2015)
Research of Error Analysis and Positioning Accuracy with Four-Prism of Laser Scanning
Yang Mengmeng, Wan Youchuan, and Xu Jingzhong
The error model of four-prism based on the unique scan four-prism tower mirror of domestic airborne laser scanner is put forward. And the position error models in horizontal and vertical direction are established respectively. The effect of positioning accuracy in qualitative and quantitative aspects are analyzed. The The error model of four-prism based on the unique scan four-prism tower mirror of domestic airborne laser scanner is put forward. And the position error models in horizontal and vertical direction are established respectively. The effect of positioning accuracy in qualitative and quantitative aspects are analyzed. The analysis demonstrates that the influence of error in the vertical and horizontal direction is different, which is related to the scanning angle and increases with the increasing of scanning distance . The vertical error in X direction is bigger than Y、Z directions. The influence of horizontal error is parabolic trend in Y direction, and seems like the influence of roll in Z direction. The analysis shows that the four-prism tower mirror error has the significant influence on the positioning accuracy, the three links of the design and processing of the mirror, the integrated of components and the host system calibration must be strict controlled in order to eliminate or weaken this error, the study of error has the important influence on improve the airborne laser radar system positioning accuracy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 914001 (2015)
Sensor Model and Simulation of Molecular Vibration Spectroscopy Based on Graphene Nanoribbon Arrays
Deng Wei, Yang Jingjing, Yan Su, Yang Jianfeng, and Huang Ming
Molecular vibration spectrum is an important fingerprint for the identification of material properties and characteristics, which has been widely used to determine molecular structure, identify unknown compounds and analyze hybrid components. A molecular vibration spectroscopy sensor based on the graphene nanoribbon arMolecular vibration spectrum is an important fingerprint for the identification of material properties and characteristics, which has been widely used to determine molecular structure, identify unknown compounds and analyze hybrid components. A molecular vibration spectroscopy sensor based on the graphene nanoribbon arrays is presented, and validated by numerical simulation. The results show that the transmission bandwidth of the graphene nanoribbon arrays can be flexibly controlled via tuning the chemical potential, period and duty ratio. The transmission coefficient of the sensor is consistent with the corresponding absorption spectrum after deposition of sample substance in the detected zone, which allows for the identification of molecular fingerprint. Moreover, the sensor has good robustness since the envelope of the transmission coefficient is independent on the thickness of the deposited sample substance..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 914002 (2015)
Study of All-Fiber Coherent Doppler Lidar Wind Profile Nonlinear Least Square Retrieval Method and Validation Experiment
Diao Weifeng, Liu Jiqiao, Zhu Xiaopeng, Liu Yuan, Zhang Xin, and Chen Weibiao
An eye-safe all-fiber coherent Doppler wind lidar system is developed. The system employs an all-fiber single-frequency polarization-maintaining laser as emission light at 1550 nm. The laser has pulse energy of 0.2 mJ, repetition frequency of 10 kHz and pulse full width half maximum of 400 ns, and the linewidth is lessAn eye-safe all-fiber coherent Doppler wind lidar system is developed. The system employs an all-fiber single-frequency polarization-maintaining laser as emission light at 1550 nm. The laser has pulse energy of 0.2 mJ, repetition frequency of 10 kHz and pulse full width half maximum of 400 ns, and the linewidth is less than 1 MHz. The aperture of the receiver-telescope and scanner of lidar is 100 mm. The system is operated in velocity azimuth display (VAD) scanning mode for wind speeds measurement at different azimuths. The mixing echo signal is received by balanced detector and sampled by 1 G/s analog to digital (AD) acquisition card, then 1024 points fast Fourier transform (FFT) and spectrum accumulation of echo signal at every range gate are implemented in the field programmable gate array (FPGA) signal processor. For the line of sight wind speeds at each azimuth, the nonlinear least square method is used to retrieve three-dimensional wind field vector measured by lidar. The wind speed measured by lidar is compared with that of wind profile radar. Correlation coefficients of horizontal wind speed, wind direction and vertical wind speed of them are 0.988, 0.941 and 0.966..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 914003 (2015)
Extracting and Plane Segmenting Buildings from Large Scene Point Cloud
Lu Weixin, Wan Youchuan, He Peipei, Chen Maolin, Qin Jiaxin, and Wang Siying
A new approach for extract and segment building target from terrestrial laser scanner point clouds is presented. The local geometric features (optimal radius, normal, dimensional feature) of each point are calculated by principal component analysis of progressive radius. The points of ground are removed from original pA new approach for extract and segment building target from terrestrial laser scanner point clouds is presented. The local geometric features (optimal radius, normal, dimensional feature) of each point are calculated by principal component analysis of progressive radius. The points of ground are removed from original point clouds by geometrical characteristic, so that the rest points can be divided into several point-clusters by distance. The statistics features of each point-cluster are calculated to extract the buildings. A growing rule based on the local geometric features is made to segment the buildings into surfaces. The experimental results show that the proposed method has the ability to extract and segment building form wide scene. Besides, the stability and accuracy of building segmenting by the proposed method is higher than that by traditional region growing method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 914004 (2015)
Study on Measuring Concentration of Ammonia and Sulphur Dioxide by Differential Optical Absorption Spectrometry Based on Fast Fourier Transform
Yu Minjie, Liu Minghui, Dong Zuoren, Sun Yanguang, Cai Haiwen, and Wei Fang
For the overlap of the absorption spectrum of NH3 and SO2 from 196 nm to 214 nm, based on differential optical absorption spectrometry and fast Fourier transform to measure concentration of gases, a method that detecting these two gases simultaneously at two wave length bands is proposed. The crosstalk effects between For the overlap of the absorption spectrum of NH3 and SO2 from 196 nm to 214 nm, based on differential optical absorption spectrometry and fast Fourier transform to measure concentration of gases, a method that detecting these two gases simultaneously at two wave length bands is proposed. The crosstalk effects between the characteristic spectrum of NH3 and SO2 are solved. The interference of SO2 to NH3 which is caused by the nonlinearity of the absorption of SO2 with the increase of its concentration within 196~214 nm wavelength band is corrected, then the real concentration of NH3 are obtained. The signal to noise ratio is improved by empirical mode decomposition (EMD) noise reduction method. The measurement error of NH3 concentration is within ± 0.15 mL/m3 , ang the relative error is less than ±1.5%. The detectable concentration limit is 1.5 mL/m3. For SO2, the measurement error is within ±2 mL/m3, and the relative error is less than ±1%. The detectable concentration limit is 16 mL/m3..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 915001 (2015)
Multipath Real-Time Measurement of Temperature and H2O Concentration for Combustion Diagnosis
Sun Pengshuai, Zhang Zhirong, Cui Xiaojuan, Wu Bian, Xia Hua, Pang Tao, Han Luo, Wang Yu, and Dong Fengzhong
Tunable diode laser absorption spectroscopy (TDLAS) has been widely used in combustion diagnosis because of its excellent characteristics such as fast response, high sensitivity and non-intrusive feature. The system uses a pair of H2O absorption lines (1395.51 nm and 1395.69 nm) by a narrow linewidth and tunable waveleTunable diode laser absorption spectroscopy (TDLAS) has been widely used in combustion diagnosis because of its excellent characteristics such as fast response, high sensitivity and non-intrusive feature. The system uses a pair of H2O absorption lines (1395.51 nm and 1395.69 nm) by a narrow linewidth and tunable wavelength distributed feedback (DFB) laser. The laser is divided into four beams by a 1×4 optical fiber splitter to measure the temperature and H2O concentration simultaneously. Sectional measurement is proposed to improve the temperature accuracy from 10% to 3% compared with K-type thermocouple. What′s more, the temperature and H2O concentration at combustion center position are measured while the ratio of air and fuel changes. The results show that combustion temperature of central area at the three kinds of combustion state has difference of about 80 K, and the H2O concentration change is well consistent with temperature change, demonstrating the stability and feasibility of the experimental setup and the data processing method. This provides strong support for tomographic diagnosis and optimization of combustion efficiency of coal-fired boiler in the future..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 915002 (2015)
Baseline Correction Method for Raman Spectra Based on Generalized Whittaker Smoother
Yang Guiyan, Li Lu, Chen He, Chen Siying, Zhang Yinchao, and Guo Pan
Raman spectrum is the characteristic spectrum for material structure and composition research as its frequency, intensity and polarization can characterize the peculiar properties of the scatterer, and thus it has been widely applied in many fields. However, the baseline drifting often occurs in the Raman spectrum and Raman spectrum is the characteristic spectrum for material structure and composition research as its frequency, intensity and polarization can characterize the peculiar properties of the scatterer, and thus it has been widely applied in many fields. However, the baseline drifting often occurs in the Raman spectrum and adversely affects its quantitative analysis. In order to eliminate the baseline drifting, a correction algorithm is presented, which combines the peak detection method based on derivative spectrum and the Whittaker smoother for baseline estimation. The spectral peak region is detected and identified utilizing the second derivatives. Then the Whittaker smoother calculates the curve fitting of the non- peak region combining the identification information, and interpolates the peak region baseline smoothly at the same time. The whole baseline estimation of the spectrum is obtained. The algorithm has been applied to simulated and actual Raman signals to correct the baseline drifting. The results show that the algorithm realizes spectral denoising and baseline estimation simultaneously. The improved analytical results of principal component analysis also verify its effect..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 9, 915003 (2015)
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