Journals >Chinese Journal of Lasers
Contents
2011
Volume: 38 Issue 7
47 Article(s)
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Research Article
Turbulence Distance of Partially Coherent Cosh-Gaussian Array Beams
Liu Fei, and Ji Xiaoling
Based on the extended Huygens-Fresnel principle, the expression for the turbulence distance of partially coherent cosh-Gaussian (ChG) array beams propagating through atmospheric turbulence is derived by using the quadratic approximation of Rytov′s phase structure function and the integral transform technique. It is shoBased on the extended Huygens-Fresnel principle, the expression for the turbulence distance of partially coherent cosh-Gaussian (ChG) array beams propagating through atmospheric turbulence is derived by using the quadratic approximation of Rytov′s phase structure function and the integral transform technique. It is showed that the turbulence distance depends on the atmospheric turbulence intensity, the beam parameters (i.e., the beam number, the beam coherence parameter, the decentered parameter, the relative separation distance of beams), the type of the beam superposition (i.e., the superposition of the cross-spectral density function and the superposition of the intensity) and so on. It is also showed that the turbulence distance of the partially coherent ChG array beams will increase with the atmospheric turbulence intensity, but the effect of turbulence on the spreading of partially coherent ChG array beams can be reduced by choosing the suitable beam parameters and the suitable type of the beam superposition..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 713001 (2011)
Laser Manufacturing
Particle Behavior of in-situ Synthesized TaC in Laser Clad Coating
[in Chinese]
NiCrBSi+Ta composite coating is produced on surface of a medium carbon steel substrate by laser cladding in order to in situ synthesize TaC particle. Scanning electron microscope (SEM), energy-dispersive spectrometer (EDS) and X-ray diffractometer (XRD) are used to observe and analyze the coating. Morphology, distributNiCrBSi+Ta composite coating is produced on surface of a medium carbon steel substrate by laser cladding in order to in situ synthesize TaC particle. Scanning electron microscope (SEM), energy-dispersive spectrometer (EDS) and X-ray diffractometer (XRD) are used to observe and analyze the coating. Morphology, distribution and formation mechanism of in situ synthesized TaC particle are discussed. In spite of high melting point, equiaxial and flower-like TaC particles are still formed by one-step laser cladding. The result shows that the formation mechanism of TaC particle is nucleation and growth, colliding and sintering, and in situ precipitating. The distribution of particles is homogeneous. Most of TaC particles are entrapped at grain boundaries instead of being engulfed by matrices or pushed to the top of the coating due to high convection, high thermal gradient, multidirectional solidification of matrix dendrites and difference between thermal conductivities of particle and matrix. The entrapment at grain boundaries is favorable for the homogeneous distribution of particles. Acicular chromium borides or carbides are found to grow up around boundaries of TaC particles, which will be beneficial for cohesion strength between particle and matrix. High amount of Si element dissolved in in-situ synthesized TaC particles is also found as compared to other carbides such as TiC, which will supply a new method to control the Si content in ceramic particle strengthening materials..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 703001 (2011)
Temperature Field Simulation and Experiment for Truing and Dressing of Bronze-Bonded Diamond Grinding Wheel with Pulsed Laser
Chen Genyu, Yu Chunrong, Li Shichun, Sun Kangjian, and Bu Chun
Based on interaction between laser and matter, the research on truing and dressing bronze-bonded diamond grinding wheel by acoustic-optic Q-switched YAG pulsed laser is carried out. Simulation models of single pulsed laser ablating bronze and diamond temperature field are established by finite element method, which shoBased on interaction between laser and matter, the research on truing and dressing bronze-bonded diamond grinding wheel by acoustic-optic Q-switched YAG pulsed laser is carried out. Simulation models of single pulsed laser ablating bronze and diamond temperature field are established by finite element method, which shows the temperature distribution of bronze and diamond under different laser power densities. Reasonable laser parameters are obtained from the temperature distribution contours: the pulsed laser power density ranging of 1.66×107~7.5×107 W/cm2 is suitable for dressing; the value ranging of 9.95×107~3.52×108 W/cm2 is suitable for truing, which can be used as reference values for practical dressing and truing experiment. Typical parameters are applied to actual truing and dressing experiment, and the surface topography of the grinding wheel becomes favorable. Through simulation and experiment, the mechanism of pulsed laser truing and dressing bronze-bond and diamond grinding wheel is further analyzed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 703002 (2011)
Microstructure and Properties of Laser Melted Layer of AZ31B Magnesium Alloy at Extreme Cooling Condition
Wang Wenxian, Chen Jianhua, Zhang Hongxia, Cui Zeqin, and Yan Xinggui
Surface of AZ31B magnesium alloy is melted using a pulsed NdYAG laser in liquid nitrogen. Then the laser melted layer cooled in liquid nitrogen is compared with that cooled in air and the substrate. The results show that the grain size of the laser melted layer cooled in liquid nitrogen is smaller than that cooled in aSurface of AZ31B magnesium alloy is melted using a pulsed NdYAG laser in liquid nitrogen. Then the laser melted layer cooled in liquid nitrogen is compared with that cooled in air and the substrate. The results show that the grain size of the laser melted layer cooled in liquid nitrogen is smaller than that cooled in air. The laser melted layer cooled in liquid nitrogen has higher micro-hardness (70～77 HV0.05) than that cooled in air(60～67 HV0.05) compared with the as-received magnesium alloy (about 55 HV0.05). The wear mass loss of the laser melted layer cooled in liquid nitrogen (1×10-3 g) is less than that cooled in air (2×10-3 g). The results indicate that liquid nitrogen is better for the enhancement of wear resistance of the laser melted layer. The experimental results show that the corrosion potential of the laser melted layer cooled in liquid nitrogen and cooled in air decrease by 22 mV and 29 mV than those of the as-received magnesium alloy respectively. This indicates that corrosion resistance of AZ31B magnesium alloys becomes worse by laser surface melting..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 703003 (2011)
Process Research on DZ125L Superalloy Parts by Laser Metal Direct Forming
Ge Jiangbo, Zhang Anfeng, Li Dichen, Zhu Gangxian, Lu Qiaopan, He Bin, and Lu Zhongliang
In order to obtain smooth surface of thin-walled parts, single-trace cladding experiments are carried out for DZ125L superalloy by laser metal direct forming (LMDF) technology using different combinations of process parameters. Influence of the process parameters (such as laser power, scanning velocity, powder mass floIn order to obtain smooth surface of thin-walled parts, single-trace cladding experiments are carried out for DZ125L superalloy by laser metal direct forming (LMDF) technology using different combinations of process parameters. Influence of the process parameters (such as laser power, scanning velocity, powder mass flow rate and Z-increment ) on height, width, aspect ratio and forming quality of single-trace cladding layer is studied systematically, by which the process parameters are optimized. In order to characterize geometrical features of single-trace cladding layer, a new method of three-dimensional (3D) characterization of energy density is proposed and the corresponding formulas are derived. From aspect ratio, dilution rate and energy density, the matching relationship between good cladding layer and its process parameters is clarified, which provides the foundations for further research into determining the process parameters according to design of cladding layer size. Experimental results show that the forming quality of thin-walled parts is obviously improved with smooth surface and no macro-defect by optimizing the process parameters..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 703004 (2011)
Effects on Technology of Aluminizing after Laser Shock Processing in 1Cr11Ni2W2MoV Steel
Li Yuqin, He Weifeng, Li Yinghong, Wang Xuede, Long Nidong, and Liu Hailei
A new technology, aluminizing after laser shock processing (LSP), for improving the fatigue performance of 1Cr11Ni2W2MoV-steel is advanced. The fatigue lives of samples are measured by the vibration fatigue experiment. These experimental tests show that the fatigue lives of aluminizing after LSP are greatly improved. TA new technology, aluminizing after laser shock processing (LSP), for improving the fatigue performance of 1Cr11Ni2W2MoV-steel is advanced. The fatigue lives of samples are measured by the vibration fatigue experiment. These experimental tests show that the fatigue lives of aluminizing after LSP are greatly improved. The microstructures are examined by means of X-ray diffractometry (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The mechanism of fatigue life improvement is also discussed. Experimental results show that the thickness of aluminizing layer is found to increase because of this new technology, and the surface crystal of 1Cr11Ni2W2MoV-steel is distributed in a gradient manner..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 703005 (2011)
Nano-Particles Reinforced Co-Based Gradient Coating with High Wear-Resistance Prepared in-situ by Laser on Surface of Crystallizer Copper Alloy
Chen Suiyuan, Dong Jiang, Chen Jun, Liang Jing, and Liu Changsheng
Based on the compositional and structural designing of Co-based cladding materials, a nano-particle reinforced Co-based alloy gradient coating is produced by laser-inducing in-situ technique on the crysrallizer Cu alloy. The microstructure, hardness, anti-wear property and mechanism of the gradient coating are studied Based on the compositional and structural designing of Co-based cladding materials, a nano-particle reinforced Co-based alloy gradient coating is produced by laser-inducing in-situ technique on the crysrallizer Cu alloy. The microstructure, hardness, anti-wear property and mechanism of the gradient coating are studied using analysis techniques. The results show that the gradient coating is composed of three layers, which are the surface, inside structure and a metallurgical bond between the gradient coating and Cu alloy substrate. Nano-particles of Cr-Ni-Fe-C, MoNi4, Cr7C2, and WC1-x synthesized in-situ play role as a reinforced Co-base gradient coating. The number of the ceramic particles increases from the first layer to the third layer. The micro-hardness of the gradient coating increases gradually from 94 HV of the substrate to 523 HV of the outmost layer. The graphite has function of improving frictional property of the gradient coating..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 703006 (2011)
Effects of Long Pulse-Width Stray Light on Shock Wave Induced by Laser
Guan Haibing, Ye Yunxia, Wu Zhong, Zhang Lei, and Zhang Yongkang
The effects of the microsecond pulse-width stray light on the shock wave induced by the nanosecond pulse-width of master laser are studied. By adjusting the half-wave voltage loaded on the Q-crystal, the energy of the stray light can be changed. Meanwhile, the shock wave induced by the master laser would be measured byThe effects of the microsecond pulse-width stray light on the shock wave induced by the nanosecond pulse-width of master laser are studied. By adjusting the half-wave voltage loaded on the Q-crystal, the energy of the stray light can be changed. Meanwhile, the shock wave induced by the master laser would be measured by polyvinylidene fluoride (PVDF) under the condition of the unchanged pump power. The result indicates that with the increase of the energy of the stray light, the energy of the master laser decreases and the pulse width of it increases, so the power density of the master laser and the peak pressure induced by the master laser would decrease; in addition, when the whole laser energy is 6.5 J and the energy of the stray light is 2280 mJ, the aluminium foil is ablated thoroughly. According to the experimental result, the formula of the peak pressure induced by the laser has been revised, which can be applicable to the computation of the peak pressure induced by the master laser under the condition of the stray light..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 703007 (2011)
Path Planning of Laser Remanufacturing Robot Based on Reverse Engineering
Liu Lifeng, and Yang Xichen
To increase the efficiency and accuracy of laser remanufacturing, a method of path planning with combining the characteristics of reverse engineering and laser remanufacturing is presented. The following aspects are contained: obtaining point clouds by scanning the surface of worn workpieces, reconstructing of repair aTo increase the efficiency and accuracy of laser remanufacturing, a method of path planning with combining the characteristics of reverse engineering and laser remanufacturing is presented. The following aspects are contained: obtaining point clouds by scanning the surface of worn workpieces, reconstructing of repair area by reverse engineering, doing the path planning comparing with laser remanufacturing parameter. The calculation of laser processing head axis vector improves the direction and distance control accuracy of laser processing robot..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 703008 (2011)
Study on Fatigue Crack Growth Performance of 6061-T6 Aluminum Alloy after Laser Shot Peening
Zhou Jianzhong, Wang Chengdong, Huang Shu, Yang Xiaodong, Xu Zengchuang, Yang Jing, and Zhu Wei
An investigation is proposed to evaluate fatigue crack performances of compact tension (CT) specimen of 6061-T6 aluminum alloy treated by large area overlapped both-sides lasr shot peening (LSP) along given orbit using YLSS-D25A/M laser, operating at 20 ns with 1064 nm radiation. Residual stress distributions before anAn investigation is proposed to evaluate fatigue crack performances of compact tension (CT) specimen of 6061-T6 aluminum alloy treated by large area overlapped both-sides lasr shot peening (LSP) along given orbit using YLSS-D25A/M laser, operating at 20 ns with 1064 nm radiation. Residual stress distributions before and after LSP are studied, effectiveness of LSP in retarding rate of pre-cracked CT specimen as well as their fatigue fracture characteristics after LSP are also discussed. Results show that LSP can effectively decrease crack growth rate, as a consequence, fatigue life is extended by 64.4%. Macro and micro fatigue fracture morphology of fatigue cracks of CT specimen after LSP indicates that tensile stress axis is perpendicular to crack plane in expansion area while apparent fatigue striation exists on section of front view. Fatigue striation space increases with gradual growth of crack..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 703009 (2011)
Laser Physics
Experimental Study of 351 nm Propagation with High Fluence on No.9 System of SG-Ⅱ Laser Facility
Zhao Dongfeng, Wang Li, Lin Zunqi, Shao Ping, Ji Lailin, Cai Zhijian, Wu Rong, Dai Yaping, and Zhu Jianqiang
A physical design scheme of final optical assembly (FOA) to achieve 351 nm propagation with high fluence is introduced. The method of optimization design is researched and the experimental study is completed on No.9 system of SG-Ⅱ laser facility. 33 shots have been fired with beam diameter of 310 mm, laser pulse width A physical design scheme of final optical assembly (FOA) to achieve 351 nm propagation with high fluence is introduced. The method of optimization design is researched and the experimental study is completed on No.9 system of SG-Ⅱ laser facility. 33 shots have been fired with beam diameter of 310 mm, laser pulse width of 3 ns and 1053 nm energy from 1000 to 4500 J. In the process of the experiment, the most efficiency of third harmonic conversion is 69.6% and the maximum fluence of 351 nm propagation is 3.76 J/cm2. And emphasis is given on the number of contamination change inside the FOA and the process of the optical damage originating from the high fluence propagation. The results show that the first cause to the optics damage with 3 J/cm2 at 351 nm is induced by amounts of contaminants which come from the scatter laser irradiating to materials..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702001 (2011)
Dynamical Model of Acousto-Optically Q-Switched CO2 Laser
Pan Qikun, Xie Jijiang, Ruan Peng, Zhang Laiming, Li Dianjun, and Guo Jin
Six-temperature model was used to simulate the theoretical process of dynamical emission in an acousto-optically (AO) Q-switched CO2 laser. Then the result of the simulation is compared with the numerical calculation results by Q-switched pulsed laser rate equations. The numerical calculation results of the two theorieSix-temperature model was used to simulate the theoretical process of dynamical emission in an acousto-optically (AO) Q-switched CO2 laser. Then the result of the simulation is compared with the numerical calculation results by Q-switched pulsed laser rate equations. The numerical calculation results of the two theories are consistent on laser output performance. However, the tail phenomenon is different between numerical calculation results of the six-temperature model theory and rate equations theory. The former is more in agreement with the experimental results. Therefore the theory of six-temperature model more perfectly explained the process of energy transfer between the different molecular energy levels in the laser gain medium. By using the six-temperature model theory, the CO2 pulse laser output performance as a function of the output mirror transmittance is simulated, and the optimum output mirror transmittance is obtained which is consistent with the experimental results. The theoretical analysis and experimental results show that the output mirror transmittance can influence the laser output performance. Therefore the output performance of the AO Q-switched CO2 laser can be improved by optimizing the transmittance of output mirror. The measured peak power of this device is 4750 W and the pulsed width is 160 ns..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702002 (2011)
Experimental Study of Singlet Delta Oxygen Produced by Discharge
Duo Liping, Wang Zengqiang, Li Liucheng, and Jin Yuqi
The production of singlet delta oxygen by radio frequency (RF) discharge is studied experimentally. The trends of the relative yields of singlet delta oxygen as functions of different doped gases, different electrode gaps and He/O2 ratios are obtained. The dependences of singlet delta oxygen yields and electric efficieThe production of singlet delta oxygen by radio frequency (RF) discharge is studied experimentally. The trends of the relative yields of singlet delta oxygen as functions of different doped gases, different electrode gaps and He/O2 ratios are obtained. The dependences of singlet delta oxygen yields and electric efficiency on the specific input energy are analyzed. The experimental results show that the relative yield of singlet delta oxygen increases obviously by adding nitric oxide or gaseous mercury. Homogeneous glow discharges at high pressure can be achieved with the total pressure of 22.6 kPa and the oxygen partial pressure up to 4.0 kPa by reducing the electrode gap. The optimum relative yield of singlet delta oxygen is obtained with the specific input energy of 150~400 J/mmol oxygen, and the optimum electric efficiency is obtained with the specific input energy of 150 J/mmol oxygen..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702003 (2011)
Effects Saturation Pressure on Spray Cooling with Ammonia
Wang Hong, Yu Yongsheng, Zhu Xun, Sun Shaopeng, Liao Qiang, Ding Yudong, and Yang Baohai
Spray cooling is an efficient high heat flux cooling method. In this study, the heat transfer characteristics of the spray cooling with ammonia as coolant are experimentally investigated under different ammonia saturation pressures. The cylindrical copper acts as the heat sources with seven cartridge heaters, and two-nSpray cooling is an efficient high heat flux cooling method. In this study, the heat transfer characteristics of the spray cooling with ammonia as coolant are experimentally investigated under different ammonia saturation pressures. The cylindrical copper acts as the heat sources with seven cartridge heaters, and two-nozzles arrays are specifically designed to spray with ammonia. Experimental results indicate that the latent heat of ammonia decreases with the saturation pressure increasing, it is useful to promote the single-phase convection to convert to the nucleate boiling at the lower superheat temperature. The surface temperature and heat transfer coefficient increase with the saturation pressure of ammonia increasing but the variation trend of the superheat reverses. The maximum heat transfer coefficient of 1.48×105 W/(m2·K) is achieved with the heat flux of 310 W/cm2, the spray chamber pressure of 4.01×105 Pa and the surface temperature only of 19.5 ℃. Meanwhile, this study provides a reference in the engineering application for the high heat flux cooling technology..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702004 (2011)
Propagation of Gaussian Beam through Planar Interface
Hong Minfang, Shen Jianqi, Zhang Qiuchang, and Yu Bin
Gaussian beam has been widely employed in optical particle measurements recently, in which the light propagation and the beam′s parameters are very important to measurement results. An analytical expression of diffracted field of a Gaussian beam through a planar interface is derived based on Fresnel-Kirchhoff diffractiGaussian beam has been widely employed in optical particle measurements recently, in which the light propagation and the beam′s parameters are very important to measurement results. An analytical expression of diffracted field of a Gaussian beam through a planar interface is derived based on Fresnel-Kirchhoff diffraction integral and under paraxial approximation, which is checked with numerical calculation. Result shows that, while a Gaussian beam, which is weakly focused, propagates normally through a planar interface between materials of mismatched refractive indices, parameters of beam waist radius keep unchanged and location of the beam waist depends on the ratio of refractive indices of neighboring materials..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702005 (2011)
A BaWO4 Raman Laser with the Raman Shift of 332 cm-1
Sun Wenjia, Wang Qingpu, Liu Zhaojun, Zhang Xingyu, Wang Gongtang, Bai Fen, Lan Weixia, Wan Xuebin, and Zhang Huaijin
A 1103-nm BaWO4 Raman laser is demonstrated with a 1064 nm pump laser. A 5 mm×5 mm×46 mm BaWO4 crystal with scattering geometry X(ZZ)X configuration is employed as the active medium and its 332 cm-1 Raman mode is accomplished. At an incident pump power of 7.55 W, the first-Stokes power of 1.23 W at 1103.2 nm A 1103-nm BaWO4 Raman laser is demonstrated with a 1064 nm pump laser. A 5 mm×5 mm×46 mm BaWO4 crystal with scattering geometry X(ZZ)X configuration is employed as the active medium and its 332 cm-1 Raman mode is accomplished. At an incident pump power of 7.55 W, the first-Stokes power of 1.23 W at 1103.2 nm is obtained at a repetition rate of 17 kHz, corresponding to an optical-to-optical conversion efficiency of 16.3%. The pulse width of Raman laser is measured to be 27 ns and the peak power is 2.6 kW. The beam quality factors M2 in the two orthogonal directions are 2.0±0.2 and 1.8±0.2, respectively. The thermal focal length of the BaWO4 crystal is estimated to be -1100 mm under this condition..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702006 (2011)
GaN-Based Blue-Violet Laser Diodes Used in Anti-interfere from Fog for Proximity-Fuse
Zhang Haojun, and Zhao Jianlin
The scattering theories of molecules and Rayleigh are applied in the analysis of the deference between fog to solid targets. And GaN-based blue-violet laser diodes and infrared diodes are compounded to a dual-wavelength diodes array. The dual-wavelength diode is used to test the deferent scatterings character of the foThe scattering theories of molecules and Rayleigh are applied in the analysis of the deference between fog to solid targets. And GaN-based blue-violet laser diodes and infrared diodes are compounded to a dual-wavelength diodes array. The dual-wavelength diode is used to test the deferent scatterings character of the fog. And for this measurement, a phase-locked circuit is also used. The scattering-ratio of the GaN-based blue-violet laser diodes and infrared diodes is more than 3. Therefore, the GaN-based blue-violet laser diodes can be used in anti-interference from fog for laser proximity-fuse. The thicker of the fog density, the effect is more significant..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702007 (2011)
Mid-infrared High Energy Laser Beam Detector Array
Yang Pengling, Feng Guobin, Wang Zhenbao, Shao Bibo, Zhang Lei, Feng Gang, Yan Yan, Wu Junjie, and Wang Qunshu
The energy and power density distributions at target are important parameters for high energy system performance evaluation. A high energy laser beam detector array is developed using photoelectric and calorimetric compound method to accurately measure large area and long pulse mid-infrared laser. The detector array coThe energy and power density distributions at target are important parameters for high energy system performance evaluation. A high energy laser beam detector array is developed using photoelectric and calorimetric compound method to accurately measure large area and long pulse mid-infrared laser. The detector array consists of graphite calorimeter and PbSe photoelectric detector array, temperature and voltage amplifier, analog to digital converter and signal processor. The effective sensitive area of the system is 22 cm×22 cm, the spatial resolution is 2.2 cm, and the temporal resolution is 20 ms, with the total energy measurement uncertainty of less than 10% and the power density distribution measurement uncertainty of less than 15%. The system is very suitable for high energy and large area mid-infrared laser beam measurement..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702008 (2011)
Optimization Design of 1 J-Level Optical Parametric Chirped-Pulse Amplification System
Wang Xiangfeng, Dai Yaping, Wang Tao, and Ji Lailin
Using a three-dimensional spatial and temporal numerical model, optimization design of 1 J-level optical parametric chirped-pulse amplification system with type I noncollinear phase matching structure is discussed. With the two LiB3O5(LBO) preamplifiers and one YCa4O(BO3)3(YCOB) power amplifier, highly stable, high-conUsing a three-dimensional spatial and temporal numerical model, optimization design of 1 J-level optical parametric chirped-pulse amplification system with type I noncollinear phase matching structure is discussed. With the two LiB3O5(LBO) preamplifiers and one YCa4O(BO3)3(YCOB) power amplifier, highly stable, high-conversion-efficiency and good beam quality signal output is got by shaping the pump beam′s spatiotemporal profiles to super-Gaussian shapes, using the walk-off compensation structure and choosing the crystal′s length on each stage. This design can meet the requirement of SG-Ⅱ upgrade project′s front-end..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702009 (2011)
Anti-laser Characteristics of Hybrid Shell Structure with Liquid Metal Layer and Its Numerical Simulation
Yang Yang, and Liu Jing
In order to avoid the thermal ablation destruction induced by the laser weapon, a thin layer of liquid metal is sandwiched into the hybrid structure shell. The unique merit of this hybrid structure lies in the excellent characteristics of liquid metal in thermal conductivity and flow to rapidly dissipate the thermal enIn order to avoid the thermal ablation destruction induced by the laser weapon, a thin layer of liquid metal is sandwiched into the hybrid structure shell. The unique merit of this hybrid structure lies in the excellent characteristics of liquid metal in thermal conductivity and flow to rapidly dissipate the thermal energy accumulated at the radiation spot. To evaluate and understand the practicability of this defensive measure against the intense laser, a comprehensive investigation on the suitability of using liquid metal is performed to sustain the thermal ablation damage. Numerical simulations are performed on three-dimensional heat transfer problems in the composite structure embedded with liquid metal. It is found that the new method can effectively reduce the temperature at the shell surface, which subsequently delays the softening process, and then achieves a powerful ability to withstand the intense laser. The strategy is expected to be useful in a variety of anti-laser systems..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702010 (2011)
Optimalized Design of Micro-channel Heat Sinks with Orthogonal Simulation
Wang Yaqing, Liu Dong, Liu Minghou, Wang Lu, and Guo Hong
The brand-new micro-channel heat sinks are designed using plug-in fins and simulated. The impact factors, namely coolant, flow rate and heat sink geometry, are considered in the study of the flow and heat transfer performance of heat sink. The optimal operating condition is obtained by the method of orthogonal simulatiThe brand-new micro-channel heat sinks are designed using plug-in fins and simulated. The impact factors, namely coolant, flow rate and heat sink geometry, are considered in the study of the flow and heat transfer performance of heat sink. The optimal operating condition is obtained by the method of orthogonal simulation by considering the notability of each factor. It is found that the orthogonal simulation method can save cost both in time and money. The orthogonal simulation method performs well in the design of channel sink..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702011 (2011)
Study of Target-in-the-Loop Fiber Laser Array Adaptive Phase-Locking Technique
Tao Rumao, Ma Yanxing, Dong Xiaolin, Si Lei, Zou Yongchao, Zhou Pu, and Liu Zejin
The target-in-the-loop (TIL) fiber laser array adaptive phase-locking technique is studied theoretically and experimentally. The system configurations of TIL adaptive phase-locked fiber laser array and the fundamental theory for single-dithering algorithm are introduced. The performance of TIL adaptive phase-locked fibThe target-in-the-loop (TIL) fiber laser array adaptive phase-locking technique is studied theoretically and experimentally. The system configurations of TIL adaptive phase-locked fiber laser array and the fundamental theory for single-dithering algorithm are introduced. The performance of TIL adaptive phase-locked fiber laser array under high-power laser is studied. Two high-power fiber amplifiers are set up and the adaptive phase-locking of two 10-W-level fiber amplifiers is accomplished by implementing single-dithering algorithm on a signal processor. The experimental results demonstrate that the optical phase noise for each beam channel can be effectively controlled by the TIL adaptive optics system and the fringe contrast is increased to 73%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702012 (2011)
Amplification Characteristic of Low Temperature Yb:YAG Crystal Disc Cooled by Alcohol
Zhang Zhenhua, Cheng Xiaojin, Wang Jianlei, Li Lei, Yang Zhongguo, Shi Xiangchun, and Chen Weibiao
We describe a low temperature Yb:YAG crystal disc laser amplifier cooled by alcohol and stuided detailed the re-absorption of Yb:YAG crystal at different temperatures. The amplifier′s characteristic has a decided change with different temperatures. For double-pass amplifier, the small signal gain of 3 is obtained at thWe describe a low temperature Yb:YAG crystal disc laser amplifier cooled by alcohol and stuided detailed the re-absorption of Yb:YAG crystal at different temperatures. The amplifier′s characteristic has a decided change with different temperatures. For double-pass amplifier, the small signal gain of 3 is obtained at the temperature of 213 K when the pump energy is 2.17 J. For four-pass amplifier, the output energy of 60 mJ per pulse is obtained, corresponding to a small signal gain of 9..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702013 (2011)
High-Power Fiber Laser Amplifiers Based on a New Pump-Coupling Technology
Zhao Baoyin, Duan Kailiang, Zhao Wei, Zhang Entao, and Hui Xiangyun
By constructing the coupled-mode equations, the mode-coupling characteristics between the passive and active cores within a kind of composite structural fiber (CSF) are studied theoretically. By using the steady-state rate equations and the heat conductive equations, the gain characteristics and the temperature distribBy constructing the coupled-mode equations, the mode-coupling characteristics between the passive and active cores within a kind of composite structural fiber (CSF) are studied theoretically. By using the steady-state rate equations and the heat conductive equations, the gain characteristics and the temperature distribution of all-fiber laser amplifiers based on CSF are calculated and analyzed numerically. The results show that the mode-coupling characteristics depend on the coupled modes, the radius and the separation of the two cores of the CSF. Compared with the end-pumped fiber laser amplifiers, the amplifiers based on CSF have a slow pump light absorption and conversion, and thus, have low temperature distribution. This kind of new coupling-pump technology by using CSF is of apparent advantages. It can be used to solve the problem of high temperature of end-pumped fiber amplifiers, and thereby provides a new approach to design higher power fiber lasers and fiber amplifiers..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702014 (2011)
Backwards Propagation Characteristics of Distorted Reflected Beams with Cat-Eye Effect
Zhao Yanzhong, Sun Huayan, Zhang Laixian, and Zheng Yonghui
Based on the generalized Collins diffraction integral and the method of expanding the aperture function into a finite sum of complex Gaussian functions, an approximate three-dimensional analytical formula for oblique detected laser beam passing through a cat-eye optical lens with center shelter and oblique detector is Based on the generalized Collins diffraction integral and the method of expanding the aperture function into a finite sum of complex Gaussian functions, an approximate three-dimensional analytical formula for oblique detected laser beam passing through a cat-eye optical lens with center shelter and oblique detector is derived. Propagation characteristics of the distorted reflected beam are performed by numerical calculation. The results show that the incident angle and the oblique angle of the detector create unsymmetrical distortions of the distribution and a certain departure from the return centre. The reflected beam will become a distorted hollow beam because of the existent of the incident angle and the center shelter. The reflected beam gradually evolves into a solid single peak beam with the increase of the propagation distance..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702015 (2011)
Study of High-Efficiency Conduction Cooling Technique for High Power Space-Based All-Solid-State Lasers
Liu Dan, Xie Kedi, Ma Xiuhua, Zhu Xiaolei, and Chen Weibiao
The novel high power micro-gravity heat pipes are applied for the conduction cooling of a high power and high repetition space-based all-solid-state laser. The waste heat of laser amplifiers can be dissipated effectively and thereby the laser output with high beam quality and high power is obtained. In view of the pumpThe novel high power micro-gravity heat pipes are applied for the conduction cooling of a high power and high repetition space-based all-solid-state laser. The waste heat of laser amplifiers can be dissipated effectively and thereby the laser output with high beam quality and high power is obtained. In view of the pumping laser diode (LD) stacks and slab gain medium being major thermal sources in slab amplifiers, the novel amplifier structures for heat dissipating are designed. In the experiment, the heat-sinking capability of two stage simulated amplifiers in series is measured with the single-channel micro-gravity heat pipe and the two-channel micro-gravity heat pipe, respectively. The experimental results show that the temperature of both stage pre-amplifiers stabilizes in the range of operating temperature for the laser diode array. In the end, the average output power more than 20 W, magnification times greater than 20, M2x of 1.42 and M2y of 1.31 are achieved successfully..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702016 (2011)
1550 nm Passively Mode-Locked Fiber Laser with a Semiconductor Saturable Absorber Mirror
Liu Pengzu, Hou Jing, Zhang Bin, and Chen Jinbao
A design of passively mode-locked fiber laser which can produce nanosecond pulses with high repetition frequency is presented. Inserting a semiconductor saturable absorber mirror (SESAM) in a Fabry-Perot (F-P) cavity, using all negative dispersion fiber, without any pulse compression mechanism, a pulse whose width is 1A design of passively mode-locked fiber laser which can produce nanosecond pulses with high repetition frequency is presented. Inserting a semiconductor saturable absorber mirror (SESAM) in a Fabry-Perot (F-P) cavity, using all negative dispersion fiber, without any pulse compression mechanism, a pulse whose width is 1 ns and repetition frequency is 10.74 MHz is achieved at a pump power of 75 mW. The spectral analysis shows that the 3 dB width is smaller than 0.1 nm. When the pump power goes to 130 mW, a maximal power of about 20.5 mW is generated. The experiment indicates that the passively mode-locked fiber laser with an SESAM can obtain a nanosecond pulse with high repetition frequency when all negative dispersion fiber is used..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702017 (2011)
Measurement and Metrology
Research of Eliminating Occlusion in Visual Construction of ThreeDimensional Objects
He Bingwei, Lin Dongyi, Chen Zhipeng, and Ding Hui
How to solve the occlusion problem effectively is a difficult subject during the progress of acquiring unknown object’s threedimensional (3D) digital model. So a new view planning which can cope with occlusion correctly is proposed. The reconstruction progress is divided into two steps: 360°side surface reconstruHow to solve the occlusion problem effectively is a difficult subject during the progress of acquiring unknown object’s threedimensional (3D) digital model. So a new view planning which can cope with occlusion correctly is proposed. The reconstruction progress is divided into two steps: 360°side surface reconstruction and upper surface reconstruction. Firstly, the contour predictable model of the occlusion is acquired and the position coping with the occlusion information is obtained with the visible region. Secondly, after the completion of side surface reconstruction, the visible criterion of the boundaries of the upper surface of the object is predicted and the best turnover angle of the vision system is defined where the vision system can acquire the maximal information of the upper surface. And then, the normal vector of the line connecting the occlusion boundary points is calculated, based on which a planning scheme to solve the occlusion is proposed. Finally, the experimental result of reconstructing the 3D real model shows that the method is feasible in practical implementation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 708001 (2011)
Application of the Optical Fiber Prober in Measuring Micro Deep Hole of Small Laser
Liu Jianping, Liang Liping, Huang Yun, and Jin Shilong
For the role with a diameter of less than 1 mm, a depth more than 10 mm, and a larger ratio of length and diameter, it is difficult to measure these micro deep holes with traditional method. In order to solve this problem, a measurement that combines the contacting measurement and the optics measurement is introduced. For the role with a diameter of less than 1 mm, a depth more than 10 mm, and a larger ratio of length and diameter, it is difficult to measure these micro deep holes with traditional method. In order to solve this problem, a measurement that combines the contacting measurement and the optics measurement is introduced. By inserting and optical fiber probe with a lighting ball in its end into the role, the ball is pushed with the contraction between the ball and the hole during the xy movement of the piece. The xy coordinate of the ball can be gotten after processing the image of the lighting ball which is captured by the CCD camera. With a fitting of many measure points, the measurements of the diameter, the cylindricity and the straightness etc. of the hole are finally realized. The measurement precision is improved through using sub-pixel detection technology. At last the system is verified through zero degree standard circle, and the repeatability uncertainty of measurement result is less than 0.4 μm. A hole with a depth of a hole with 15 mm and a diameter of about 0.6 mm is measured in a 3D measurement microscope, and the experiment provides a suitable method to measure the hole with big ratio of length and diameter..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 708002 (2011)
Speckle Noise Reduction Algorithm Based on Principle of Shearing Interferometry
Qian Xiaofan, Rao Fan, Lin Chao, and Li Bin
Denoising operation is usually needed for obtaining the phase of optical field by optical interferometry, and current denoise algorithms can achieve good results when the phase of optical field changes slowly. If the phase has high spatial variation frequency, the conventional denoise algorithms often cause loss of phaDenoising operation is usually needed for obtaining the phase of optical field by optical interferometry, and current denoise algorithms can achieve good results when the phase of optical field changes slowly. If the phase has high spatial variation frequency, the conventional denoise algorithms often cause loss of phase detail and fringe breaks. For this reason, by introducing shearing of optical field to reduce the frequency significantly and separating the speckle noise from optical field, a new denoise algorithm and corresponding theoretical analysis are presented. The validity of this new algorithm is showed in one simulated result and one experimental example of denoising; and the obtained phase approaches experimental value well, proved that this new algorithm is better than conventional algorithms..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 708003 (2011)
Thermometry of Cr Laser Cooling via Knife-Edge
Jiao Xiaoguang, Yin Cong, Shi Chunying, and Qian Jin
The principle of knife-edge thermometry is introduced. A chromium beam which is jetted from high temperature atomic crucible is collimated by one-dimensional laser Doppler cooling on self-designed system of chromium atom lithography. The laser wavelength in vacuum is 425.5 nm, corresponding to 7S3→7P04 transition of 52The principle of knife-edge thermometry is introduced. A chromium beam which is jetted from high temperature atomic crucible is collimated by one-dimensional laser Doppler cooling on self-designed system of chromium atom lithography. The laser wavelength in vacuum is 425.5 nm, corresponding to 7S3→7P04 transition of 52Cr. The setup of knife-edge thermometry is designed and built to quantify the effect of the chromium beam collimation by laser cooling. The obvious cooling phenomenon is observed with power of 45 mW, spot size of 1 mm×20 mm and detuning of -2.5 MHz. Then, based on it, the knife-edge measurement is carried out. The results show that the full-width at half-maximum (FWHM) of chromium beam angular distribution is (0.616±0.007) mrad and the transverse temperature is (418±10) μK by laser cooling. The results provide a basis for optimizing the chromium beam collimation by laser cooling..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 708004 (2011)
Optical Communication
A High-Precision Method for Determining the FBG Peak Wavelength Shift Based on FBG Actual Reflection Spectrum Match
Cui Jian, Dong Xiaopeng, Wu Zhaoxi, Su Juan, Lin Ganbin, and Wang Shuisheng
Referring to the problems in using low-resolution charge coupled device (CCD) to measure fiber Bragg grating (FBG) peak wavelength, a high-precision method for determining the FBG peak wavelength shift by matching basis function based on the FBG actual reflection and sampling data measured by CCD is proposed. The effecReferring to the problems in using low-resolution charge coupled device (CCD) to measure fiber Bragg grating (FBG) peak wavelength, a high-precision method for determining the FBG peak wavelength shift by matching basis function based on the FBG actual reflection and sampling data measured by CCD is proposed. The effectiveness and feasibility of the new method are studied theoretically and experimentally. It is proved that compared with fitting sampling data by specific functions, the matching method based on FBG actual reflection spectrum can determine FBG peak wavelength shift more accurately. In the case of few sampling data and low resolution of CCD measurement, the high-precision determination of FBG peak wavelength shift is achieved. The accuracy of demodulation of FBG peak wavelength shift using low-cost CCD in the practical applications is improved effectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 705001 (2011)
Characteristics of Distributed Feedback Semiconductor Laser Injection Locking and Applications to Optical Fiber Sensing
Zhou Huijuan, Chen Mo, Yao Qiong, and Meng Zhou
A standard commercialized fiber-pigtailed distributed feedback (DFB) laser is chosen as the slave laser to construct the master-salve laser injection locking experimental system. The basic characteristics of the slave laser at different injection powers are measured and compared, such as the stable locking range, mode A standard commercialized fiber-pigtailed distributed feedback (DFB) laser is chosen as the slave laser to construct the master-salve laser injection locking experimental system. The basic characteristics of the slave laser at different injection powers are measured and compared, such as the stable locking range, mode spectra, phase noises and output optical powers, which prove that the laser injection locking can greatly improve the spectral purity of the slave laser while almost not affect its output optical power. The locked slave laser acts like a narrow tunable optical filter and affords some power amplification as well. Moreover, the central frequency and bandwidth of the filter are completely decided by the input injection. Then, the DFB laser injection locking technology is used to extract and amplify the single frequency of Brillouin shift in Brillouin optical fiber sensing system based on electro-optic microwave modulation. Furthermore, the drift of the direct current operation point is resolved as well..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 705002 (2011)
Experimental Research on Supercontinuum Generation from Nanosecond Pulse and Conventional Single Mode Fiber
Liu Chu, Eric Rees, Toni Laurila, Jian Shuisheng, and Clemens Kaminski
1064 nm nanosecond pump pulses and conventional single mode fibers are adopted to generate supercontinuum whose spectrum covers from 700 nm to above 1750 nm. In the fiber′s normal dispersion regime, the spectrum initially shows multi Raman Stokes lines. As pump power or fiber length increases, Stokes energies enter int1064 nm nanosecond pump pulses and conventional single mode fibers are adopted to generate supercontinuum whose spectrum covers from 700 nm to above 1750 nm. In the fiber′s normal dispersion regime, the spectrum initially shows multi Raman Stokes lines. As pump power or fiber length increases, Stokes energies enter into anomalous dispersion regime and form optical solitons, which make the following spectral broadening to be dominated by soliton-related nonlinear effects. We show experimentally that the supercontinuum generates with 28 m fiber length has flat spectral structure (in less than 3 dB flatness), high spectral density (0.4 mW/nm in average) and single mode output in 1260 nm to 1750 nm regime..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 705003 (2011)
Research Transparent Characteristics of Two Cascaded Long-Period Gratings
Ruan Juan, Zhang Weigang, Geng Pengcheng, Zhang Shanshan, and Li Xiaolan
The model of two long-period gratings cascaded with different periods, lengths and gap is proposed. The transmission spectrum is analyzed by utilizing transfer matrix and coupled-mode theory. Theoretical analysis indicates the gap of cascaded long-period gratings (CLPG) has the least effect on the position of loss peakThe model of two long-period gratings cascaded with different periods, lengths and gap is proposed. The transmission spectrum is analyzed by utilizing transfer matrix and coupled-mode theory. Theoretical analysis indicates the gap of cascaded long-period gratings (CLPG) has the least effect on the position of loss peaks. In certain wavelengths region the simulative spectrum is a straight line for particular structure of CLPG. The transparent phenomenom is observed and the condition of gratings transparency is obtained according to the model proposed. The transmissivity of CLPG is almost 0 dB as the periods and lengths of gratings are properly adjusted to match the transparent condition. The transparent phenomenom is verified by experiment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 705004 (2011)
Impact Analysis of Setting Parameter of Movable LargeZone Furnace FiberTapering System to Shape of Tapered Fibers
Sun Weimin, Yuan Ming, Zeng Xianjin, and T. A.
The calculation formula for the shape of tapered fibers in movable largezone furnace fibertapering system is derived by the discrete deducing method. We analyze the influences of some setting parameters of the movable largezone furnace fibertapering system, such as moving distance, moving speed of the furnace and mThe calculation formula for the shape of tapered fibers in movable largezone furnace fibertapering system is derived by the discrete deducing method. We analyze the influences of some setting parameters of the movable largezone furnace fibertapering system, such as moving distance, moving speed of the furnace and moving speed of the holders, on the shape of tapered fibers. The impact to the shape of the fiber waist is discussed primarily. It is found that the furnace moving distance affects the fiber waist length and radius greatly, while the moving speed of the furnace and the holders can effect the fiber waist radius visibly. However, both the speed of the furnace and the holders cannot affect the fiber waist length obviously. All these results are important for the largezone furnace fibertapering technology..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 705005 (2011)
Supermode Coupling Characteristics of Linear-Core-Array Fiber
Zhu Xiaoliang, and Yuan Libo
The theoretical prediction and experimental study of 5-core-linear-array fiber are implemented in this paper according to two different excitation methods. The far field supermode distributions of 5-core-linear-array fiber are calculated and the beam qualities under two different excitation methods are also analyzed. TThe theoretical prediction and experimental study of 5-core-linear-array fiber are implemented in this paper according to two different excitation methods. The far field supermode distributions of 5-core-linear-array fiber are calculated and the beam qualities under two different excitation methods are also analyzed. The results may provide a basis for high power fiber lasers or for fiber lasers which have particular spot shape and are also helpful for similar microstructure fibers applied in laser areas..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 705006 (2011)
Error Adaptive Feedforward Composite Control of Fast-Steering-Mirror
Ding Ke, Huang Yongmei, Ma Jiaguang, and Fu Chengyu
In order to reduce beam jitter introduced by all kinds of broadband and narrowband disturbance, and improve the satellite acquisition, pointing and tracking (ATP) system′s pointing accuracy, a new kind of composite control is constructed based on the traditional proportional-integral-differential (PID) feedback algoritIn order to reduce beam jitter introduced by all kinds of broadband and narrowband disturbance, and improve the satellite acquisition, pointing and tracking (ATP) system′s pointing accuracy, a new kind of composite control is constructed based on the traditional proportional-integral-differential (PID) feedback algorithm and the new adaptive feedforward algorithm. It can reduce the jitter that satellite ATP system bears better than the traditional PID feedback algorithm. It not only has the merits of both algorithms, but also has the merit of no extra sensors for feedforward loop compared with the common adaptive feedfoward algorithms. So the algorithm will not improve cost and complexity of the system. The algorithms referred above are verified by experiments and comparisons are made. Experimental results indicate that the error adaptive feedforward composite control algorithm′s accuracy is nearly 5 times better than that of the classical PID control algorithm and 1 time better than that of the adaptive feedforward algorithm. The error adaptive feedforward algorithm can reduce beam jitter and improve the satellite ATP system′s pointing accuracy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 705007 (2011)
Bi-directional Dual-wavelength Brillouin Lasing in Hybrid Fiber Ring Cavity and Demonstration of Its Gyroscope Effect
Li Hongliang, Zhang Wei, Huang Yidong, and Peng Jiangde
Bi-directional dual-wavelength multi-mode Brillouin lasing based on the unbalanced Mach-Zehnder interferometer (UMZI) hybrid fiber ring cavity is realized experimentally with frequencies of heterodyne spectrum between pump and Stokes lights being 10.49 GHz and 10.54 GHz, respectively. Frequency shift of bi-directional Bi-directional dual-wavelength multi-mode Brillouin lasing based on the unbalanced Mach-Zehnder interferometer (UMZI) hybrid fiber ring cavity is realized experimentally with frequencies of heterodyne spectrum between pump and Stokes lights being 10.49 GHz and 10.54 GHz, respectively. Frequency shift of bi-directional Stokes light′s beat spectrum is measured, and results show that the frequency shift linearly increases with the increase of rotating speed of cavity. The lock-in effect is not observed in the range of measurement, and rotating direction of cavity can be clearly distinguished through relative frequency shift. This provides a novel way for designing Brillouin fiber-optic gyroscope (BFOG). The measured scale factor of gyroscope is 1.0305 kHz/(°·s-1), which fits well with the result of theoretical analysis..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 705008 (2011)
Rapid Communications
[in Chinese]
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Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 702010 (2011)
[in Chinese]
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 705008 (2011)
Terahertz Technology
Experiment on 2.52 THz Transmission-Mode Imaging for Concealed Objects
Li Qi, Yao Rui, Ding Shenghui, and Wang Qi
Terahertz (THz) imaging has the advantage that the THz radiation can penetrate most nonmetal and nonpolar materials for concealed objects detection, while it is harmless to organism. The penetration ability for common packaging materials and clothes thus become very important to evaluate a THz imaging system. In the paTerahertz (THz) imaging has the advantage that the THz radiation can penetrate most nonmetal and nonpolar materials for concealed objects detection, while it is harmless to organism. The penetration ability for common packaging materials and clothes thus become very important to evaluate a THz imaging system. In the paper, penetration experiments are carried out by use of a 2.52-THz transmission-mode scanning system. The system is constructed based on a CO2 laser pumped THz laser. The imaging targets are razor blade, penciled character, banknote, and plastic bottle cap. Paper, paper envelope, and lab gown are used as shelters, and the imaging results are compared and analyzed. The experimental results demonstrate that the system can image through 13 pieces of A4 paper, 2 layers of lab-gown, or 2 layers of paper envelope. The maximum attenuation approaches 50 dB..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 711001 (2011)
Optical Design and Fabrication
Optical Design of Spectrum Observation System in ZnO Temperature Sensor
Ye Biqing, Wang Fei, Sui Chenghua, Yan Bo, and Shi Wenyuan
In order to solve the measurement and integration of ZnO temperature sensor, a spectrum observation system is designed. Its spectrum range is 350～450 nm and resolution is approximately 0.1 nm. A reasonable optical structure is selected. Optical elements and light path are calculated and the aberration of system is elimIn order to solve the measurement and integration of ZnO temperature sensor, a spectrum observation system is designed. Its spectrum range is 350～450 nm and resolution is approximately 0.1 nm. A reasonable optical structure is selected. Optical elements and light path are calculated and the aberration of system is eliminated to achieve the requirements of narrow spectrum range and high resolution. The system volume is 111 mm×83 mm×30 mm, satisfying the requirement of integration. And it can be used for further optimization, tolerance analysis to meet the processing requirements..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 716001 (2011)
Study on a Novel Segmented Micro-deformable Mirror with Tip-Tilt Motion
Wang Weimin, Tao Fenggang, Yan Shengmei, Zhang Jianfei, and Yao Jun
A new segmented tip-tilt deformable mirror (DM) based on surface micromachining process is proposed, a mirror array with 3×4 elements is fabricated. In this new structure every mirror suface has one only actuator so that the mirror array has a continuous surface topography, and the residual stress in the fabricatiA new segmented tip-tilt deformable mirror (DM) based on surface micromachining process is proposed, a mirror array with 3×4 elements is fabricated. In this new structure every mirror suface has one only actuator so that the mirror array has a continuous surface topography, and the residual stress in the fabrication process can be effectively released with a result that the curl of the surface is reduced. The resonance frequency and the relationship between displacement and voltage are calculated based on the theory of elasticity and simulated based on a finite elements analysis (FEA) software. Then the fabricated device is tested by an optical profiler. Experimental results indicate that the actuated array has a piston-tip-tilt (PTT) motion, and the mirror has a stroke of approximately 0.76 μm under 3.75 V driving voltage, which is coincident with the theoretical analysis. Compared with previous reported segmented tip-tilt DM, this new structure has a lower working voltage and a fewer amount of actuators, and provides a possibility of integrating a large-actuator-count DM with integrated circuit (IC) on one chip..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 716002 (2011)
Spectroscopy
Coherent Anti-Stokes Raman Spectroscopy Study in the Na2(A1∑+u)-H2 Collision
Cai Qin, Zhang Liping, Luan Nannan, Cheng Yufeng, Dai Kang, and Shen Yifan
Coherent anti-Stokes Raman spectroscopy (CARS) has been used to analyze the internal state distribution of H2 after energy transfer with Na2(A1∑+u). The scanned CARS reveals that during energy transfer processes H2 molecules are produced at the V=1, 2 and 3 vibrational levels. Two possible populations ratios (n1/n2) arCoherent anti-Stokes Raman spectroscopy (CARS) has been used to analyze the internal state distribution of H2 after energy transfer with Na2(A1∑+u). The scanned CARS reveals that during energy transfer processes H2 molecules are produced at the V=1, 2 and 3 vibrational levels. Two possible populations ratios (n1/n2) are obtained from scanned CARS peaks. The actual population ratio n1/n2 is determined to be 1.82 through shape simulations of the time resolved CARS profiles under a kinetic model. The n1/n2 ratio indicates that the H2 molecules produced by the energy transfer process are 0.53 populated at the V=1 level, 0.30 at V=2 and 0.17 at V=3. The relative fraction (〈ft〉, 〈fv〉, 〈fr〉) of average energy disposal is derived as 0.51, 0.46, 0.03, which has a major energy releases in vibrational and translational. This consequence supports the collinear collision geometry in ratio Na2-H2 energy transfer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 715001 (2011)
High Sensitive Detection of Trace Hg(II) in Natural Water with Laser Ignition Assisted Spark-Induced Breakdown Spectroscopy
Li Guan, Jiang Jie, Zhang Qian, Chen Yuqi, and Li Runhua
The trace Hg in natural water was electrically deposited on the surface of a high-purity copper rod which can effectively avoid the problems existed in directly analyzing aqueous solutions with plasma emission spectroscopy, such as the effect of water sputtering and atomic emissions quenching effect due to water molecuThe trace Hg in natural water was electrically deposited on the surface of a high-purity copper rod which can effectively avoid the problems existed in directly analyzing aqueous solutions with plasma emission spectroscopy, such as the effect of water sputtering and atomic emissions quenching effect due to water molecules in plasma. Discharge stability is improved and the required voltage and current for stable discharge are decreased under the assistance of laser ignition in spark-induced breakdown spectroscopy (SIBS). Laser-ignition technique is able to enhance atomic emission of Hg in spark-induced plasma. The calibration curve of Hg in natural water is built with laser-ignition assisted spark-induced breakdown spectroscopy (LI-SIBS) technique under the condition of 7.5 V deposition voltage, 10 min deposition time and 4000 V discharge voltage. Detection limit of mercury reaches to 1 μg/L under current condition. There are no any additional pollution and memory effect for Hg in this rapid and sensitive technique..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 715002 (2011)
Fluorescence Discrimination and Determination Method for Phytoplankton Composition by SA4 Multiwavelet
Zhang Cui, Su Rongguo, Zhang Shanshan, Duan Yali, and Wang Xiulin
A fluorescence spectroscopy method for differentiation of phytoplankton classes is developed. SA4 multiwavelet functions are used to decompose the three-dimensional (3D) fluorescence spectra date of 42 phytoplankton species dominant in coastal area of China sea into scale vectors and wavelet vectors, then the Ca2, Ca3 A fluorescence spectroscopy method for differentiation of phytoplankton classes is developed. SA4 multiwavelet functions are used to decompose the three-dimensional (3D) fluorescence spectra date of 42 phytoplankton species dominant in coastal area of China sea into scale vectors and wavelet vectors, then the Ca2, Ca3 and Ca2-Ca3 vectors are chosen as fluorescence feature spectra by Bayesian discriminant analysis and the three kinds of reference spectra are obtained by application of the systematic cluster to the fluorescence feature spectra, based on which, a fluorescence spectroscopy method is developed by multivariate linear regression resolved by nonnegative least squares. The three kinds of reference spectra are utilized to the samples composed of one phytoplankton species, the results suggest that the Ca2 reference spectra are the strongest: the average correctly discriminating rate are 96.1% at the division level and 87.4% at the genus level. For the simulative mixed samples, the correctly discriminating rate for dominant species ranged from 91.4% to 100%, the average are 98.0%, 99.4%, 99.9%, the average relative content are 72.7%, 77.1%, 86.1% at division level, the correctly discriminating rate for dominant species ranged from 23.2% to 100% and the average are 91.2%, 92.5%, 93.4% at genus level in three different ratios respectively. For the mixed samples in lab, the correctly discriminating rate for dominate species range from 60.0% to 100%, the average is 97.0%, and the average relative content is 71.8% at division level; the correctly discriminating rate for dominate species range from 25.0% to 100%, the average is 83.1% at genus level. For the samples from the mesocosm experiment in Maidao Bay of Qingdao and Jiaozhou Bay, the discriminating results of dominant phytoplankton classes from the fluorescence spectroscopy method are the same as that of microscopic examination at division level, and for the 10 samples with over 75% relative dominance of one phytoplankton species, the dominant species of 7 samples are recognized at genus level..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 7, 715003 (2011)
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