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2014
Volume: 41 Issue 10
44 Article(s)
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Research Article
All Sky Turbid Atmospheric Polarization Pattern Modeling Based on Monte Carlo Method
Wang Ziqian, Zhang Xudong, Jin Haihong, and Fan Zhiguo
Atmospheric polarization pattern contains a plenty of informations, such as informations of the spatial orientation, characteristics of earth′s surface, structure parameters of the atmosphere, et al, which has important research value in polarotactic navigation, remote sensing, and other fields. However, the real celesAtmospheric polarization pattern contains a plenty of informations, such as informations of the spatial orientation, characteristics of earth′s surface, structure parameters of the atmosphere, et al, which has important research value in polarotactic navigation, remote sensing, and other fields. However, the real celestial polarization pattern in the turbid atmosphere is quitely different from simulation results of existing classical models, which cannot represent the atmospheric polarization pattern in turbid atmosphere. A turbid simulation model of atmospheric polarization pattern is proposed. This new model can be set up by using the three dimension (3D) celestial sphere model to describe the real atmosphere, using the Monte Carlo program of polarized light transport to simulate radiation transfer of the sunlight in the atmosphere. The experiments show that this model is consistent with the real polarization pattern in turbid atmosphere. Specifically the degree of polarization distribution highly accords with the real degree of polarization distribution. And the angle of polarization distribution can reflect the distribution and change feature of the real angle of polarization accurately. In conclusion, this model can be used to analyze and predict the distribution and change feature of the real atmospheric polarization pattern in turbid atmosphere..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1013001 (2014)
Influence of Non-Kolmogorov Turbulence on the Rayleigh Range and Turbulence Distance of Gaussian-Schell Beams
Tang Mingyue, Li Binzhong, Wang Yufeng, and Chen Xiaowen
The expressions of the Rayleigh range zR and turbulence distance zT of Gaussian-Shell model (GSM) beams propagating through non-Kolmogorov turbulence are derived, and the influence of turbulence parameters (generalized exponent parameter α、 inner scale l0and outer scale L0) on the spreading of partially coherent beams The expressions of the Rayleigh range zR and turbulence distance zT of Gaussian-Shell model (GSM) beams propagating through non-Kolmogorov turbulence are derived, and the influence of turbulence parameters (generalized exponent parameter α、 inner scale l0and outer scale L0) on the spreading of partially coherent beams is studied. It is shown that zR decreases firstly and then increases due to increasing α. When α=3.11, zR reaches its minimum, which means that the spreading of beams is maximum. The Rayleigh range zR increases with decreasing outer scale L0 for 3.6<α<4 and increasing inner scale l0. When α>3.11, the influence of l0 on zR becomes smaller with larger α. It is worthy to be mentioned that the spreading of the beams is hardly affected by the turbulence within the Rayleigh range for small value of coherence parameter β or waist width w0, unrelated to α. Conversely, when the values of β or w0 are large enough, the spreading is affected by turbulence within Rayleigh range for different values of α. In addition, when the values of β or w0 are in a certain range, whether the spreading is affected by turbulence within Rayleigh range will be concerned with generalized exponent parameter α..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1013002 (2014)
Biomedical Photonics and Laser Medicine
Compact Optical-Resolution Photoacoustic Microscopy System Based on a Pulsed Laser Diode
Zeng Lüming, Liu Guodong, Yang Diwu, Ji Xuanrong, Huang Zhen, and Dong Jian
A compact optical-resolution photoacoustic microscopy system is designed with a pulsed laser diode, which has the properties of being low cost, small size, robust and high repetition frequency. Typical photoacoustic images of carbon fiber and blood vessel phantoms are reconstructed clearly. During the experiments, the A compact optical-resolution photoacoustic microscopy system is designed with a pulsed laser diode, which has the properties of being low cost, small size, robust and high repetition frequency. Typical photoacoustic images of carbon fiber and blood vessel phantoms are reconstructed clearly. During the experiments, the pulsed laser diode excitation is droved to implement C-mode scanning excitation with three-dimensional translation stage, and the excited photoacoustic signal is captured by a 1-3 composite ultra-bandwidth ultrasonic transducer. The photoacoustic signal-to-noise ratio is recorded of approximate 11 dB, and the lateral resolution of the current system is improved up to 1.5 μm from 500 μm of the first-generation system. The experimental results demonstrate that the proposal method has the potential to be developed as a configuration of inexpensive, real-time, portable, and high-resolution photoacoustic microscopy technique..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1004001 (2014)
Holography and Information Processing
Influence of Substrate Temperature on SiO2 Thin Films by Electron Beam Deposition
Du Qianqian, Wang Wenjun, Li Shuhong, Liu Yunlong, He Xiaoxiao, Gao Xuexi, Zhang Bingyuan, and Shi Qiang
The relationship of stacking density, refractive index and substrate temperature is obtained by statistical thermodynamics theory and thin film growth mechanism. Monolayer SiO2 thin films are fabricated at different substrate temperatures and deposition rates by electron beam evaporation technology. The relationships bThe relationship of stacking density, refractive index and substrate temperature is obtained by statistical thermodynamics theory and thin film growth mechanism. Monolayer SiO2 thin films are fabricated at different substrate temperatures and deposition rates by electron beam evaporation technology. The relationships between deposition rate and surface uniformity , the refractive index are studied. The influence of substrate temperature on the refractive index, transmittance, morphology, microstructure of thin films is emphatically analyzed. It shows that the surface roughness decreases, the crystalline grain gap narrows, the refractive index and transmittance increase, absorption degree reduces with the increasing of substrate temperature. When the substrate temperature is 500 ℃, the transmittance of SiO2 thin films in the visible light is above 99.4%. Through fitting experimental data, theory calculation agrees well with the experimental results..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1007002 (2014)
Influence Study of Inhomogeneous Beam Intensity and Polarization to Holographic Interference Structure by Computer Simulation
Lü Hao, Wang Shouzhi, and Wang Xia
In order to optimize the beam parameters further of holographic lithography experiment, based on multi-beam interference theory, the influences of inhomogeneous beam intensity and polarization to the interference patterns are simulated by the two and three linear polarization beams interference quantitatively and qualiIn order to optimize the beam parameters further of holographic lithography experiment, based on multi-beam interference theory, the influences of inhomogeneous beam intensity and polarization to the interference patterns are simulated by the two and three linear polarization beams interference quantitatively and qualitatively, respectively. Results show that the structure contrast decreases gradually with the increase of beam polarization difference and intensity heterogeneity. Furthermore, this influence diminishes as the incident angle increasing. The variation of beam polarization and intensity in three beam interference influences wave vector difference, and then alters the lattice shape and structure contrast. Theory guidance is provided to control beam polarization and intensity of holographic interference experiments, which paves a way for the fabrication and optimization of optical micro-structures..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1009001 (2014)
Laser Manufacturing
Microstructure and Mechanical Property Analysis About NiTiNb Laser Welding Joint Around Heat Treatment
Lu Weiwei, Chen Yuhua, Huang Yongde, and Fu Qiang
Laser welding of 200 μm thickness NiTiNb shape memory alloy is achieved by Nd:YAG pulse laser. The welding is annealed at 850 ℃. Microstructure and mechanical properties are analyzed by optical microscope, scanning electron microscope and precision tensile machine. The results indicate that a layered microstructure occLaser welding of 200 μm thickness NiTiNb shape memory alloy is achieved by Nd:YAG pulse laser. The welding is annealed at 850 ℃. Microstructure and mechanical properties are analyzed by optical microscope, scanning electron microscope and precision tensile machine. The results indicate that a layered microstructure occurs before heat treatment. Grains in the fusion area are epitaxial growth and the weld center are full of small isometric crystals. The tensile strength of the welding joint reach 90% of the matrix. Small and light dimples are observed on the welding joint fracture, which means it is ductile fracture. All the isometric crystals in the welding joint vanish after heat treatment, and coarse grain region and segregated spot have alternate distribution. Stress induced martensite occurs in both matrix and welding joint, which is called pseudo-elasticity. The yield strength of the welding joint with heat treatment is only 60% of the matrix. The micro-hardness of the matrix and welding joint with heat treatment is lower than those of the unheated ones..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1003001 (2014)
Microstructure and Properties of Fiber Laser Welded Joints of Motor Ultrahigh-Strength Steel 22MnB5 and 22MnB5-Q235
Jia Jin, Yang Shanglei, Ni Weiyuan, Bai Jianying, and Ding Bo
To accelerate the development of the laser welding technology of advanced high strength steel (AHSS), similar butt welding of 1.9 mm thick 22MnB5 and dissimilar tailored blank welding of 22MnB5 and Q235 are performed by using a fiber laser. The microstructure, hardness and tensile properties of weld joints are analyzedTo accelerate the development of the laser welding technology of advanced high strength steel (AHSS), similar butt welding of 1.9 mm thick 22MnB5 and dissimilar tailored blank welding of 22MnB5 and Q235 are performed by using a fiber laser. The microstructure, hardness and tensile properties of weld joints are analyzed after the fiber laser welding (FLW). The results show that the microstructure of weld zone(WZ) mainly contains lathy martensite. Heat affected zone (HAZ) in 22MnB5 can be divided into three parts: quenched zone, incomplete quenched zone and tempered zone, and the last one is absent in Q235. The hardness distribution of weld joints is non-uniform, and the weld edge has the highest hardness. HAZ is very narrow and a soft zone exists in the 22MnB5 HAZ with the lowest hardness of 319.6 HV, while there is no soft zone in Q235. With the increase of welding speed, the martensite in WZ becomes finer, leading to the increasing of hardness. When the welding speed is 5 m/min, the highest hardness of the WZ attains 544.2 HV which is the highest of all the samples. The 22MnB5 samples for tensile test which are welded at the speed from 3 to 5 m/min are all broken in HAZ, and the elongation at break is only about 2%, which is obviously worse than that of base metal (8.9%)..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1003002 (2014)
Study of Influence of Wire Feeding Speed on Properties of Laser Brazing Joint of Zinc-Coated Steel
Ma Kai, Yu Zhishui, Zhang Peilei, Lu Yunlong, Chu Zhentao, and Shi Haichuan
Many factors affect the quality of the overlap joint in the laser brazing process, such as laser power, welding speed, defocusing distance and so on. The influences of wire feeding speed on the overlap joints′ mechanical properties are studied. The results indicate that a large number of dispersed phases are found in tMany factors affect the quality of the overlap joint in the laser brazing process, such as laser power, welding speed, defocusing distance and so on. The influences of wire feeding speed on the overlap joints′ mechanical properties are studied. The results indicate that a large number of dispersed phases are found in the overlap joint, which is identified as Fe-Si(Cu). These phases appear as granular, island or petal shape. A joint with best mechanical property is got when the wire feeding speed is 2.0 m/min. Phases of Fe-Si(Cu) distribute densely in the joint. The mechanical properties of the overlap joint is best, and is higher than that of the base metal. The fracture occurs in the base metal. When the wire feeding speed is 1.7 m/min and 2.3 m/min, phases of Fe-Si(Cu) only sporadics distribute in the joint. The mechanical properties of the overlap joint is worse than that of the base metal. The fractare occurs at the brazing seam. The fracture mode is the ductile and brittle mixed fracture..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1003003 (2014)
Microstructure and Wear Property of TiC Particle Reinforced Composite Coatings on H13 Steel Surface by Laser in-situ Synthesis
Yao Shuang, Liu Hongxi, Zhang Xiaowei, Li Qi, and Zhang Xu
In-situ TiC particle reinforce composite coating is synthesized on H13 steel surface by laser cladding technique. The phase composition, microstructure, friction and wear behavior and Vickers hardness of composite coating are analyzed using X-ray diffraction (XRD), energy dispersive spectrometer (EDS), optical microscoIn-situ TiC particle reinforce composite coating is synthesized on H13 steel surface by laser cladding technique. The phase composition, microstructure, friction and wear behavior and Vickers hardness of composite coating are analyzed using X-ray diffraction (XRD), energy dispersive spectrometer (EDS), optical microscopy (OM), scanning electron microscopy (SEM), wear testing machine and Vickers hardness gage. The results show that the laser cladding composite coating is mainly composed of TiC, Cr7C3 and Fe-Cr phases under the molar ratio of Ti to Cr3C2 of 2.441 condition. The content of Cr7C3 phase in coating increases under the molar ratio Ti to Cr3C2 of 21 condition, while (Cr, Fe)7C3 phase is found under the molar ratio Ti to Cr3C2 of 22.33 condition. SEM and EDS analysis indicate that the microstructure of TiC phase gradually changes from ball shape to lamellar with the increasing of laser power density. The cladding coating surface macro morphology is good and no pores or cracks under the molar ratio Ti to Cr3C2 of 22.33 and the laser power density 24.38 kW·cm-2 condition. The highest average Vickers hardness of the laser cladding composite coating is 931.9 HV0.2, which is about 2.21 times higher than that of the H13 steel substrate. The lowest wear weight loss of the composite coating is only 27.2 % of the substrate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1003004 (2014)
Phase Analysis of Bioceramic Coatings by Laser Cladding
Bao Yumei, Gao Haiming, Xu Jingshun, Ma Long, and Xu Zheyu
Bioceramic coatings on titanium alloy (TC4) is fabricated with the powders of CaCO3,CaHPO4·2H2O and Ti by laser cladding and heat treatment. Phase analysis by X-ray diffraction (XRD) indicates that the main compose of transitional coating is CaTiO3, and the ceramic coating without heat treatment is tetracalcium phBioceramic coatings on titanium alloy (TC4) is fabricated with the powders of CaCO3,CaHPO4·2H2O and Ti by laser cladding and heat treatment. Phase analysis by X-ray diffraction (XRD) indicates that the main compose of transitional coating is CaTiO3, and the ceramic coating without heat treatment is tetracalcium phosphate (TTCP), the ceramic coating after heat treatment is hydroxyapatite (HA). It can be conclude that laser power has a greater impact on the composition of coating than scanning speed. The heat treatment process at temperature 800 ℃ for 4 hours and furnace cooling can promote the regeneration of HA and effectively increase the content of HA in ceramic layer. The HA content of coating fabricated with Ca/P2.00 powders is higher than those of others..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1003005 (2014)
Research on Focused Spot Diameter and Butt Joint Gap Margin in Laser Welding with Hot Wire Filler
Zhang Shuquan, Wu Jiefeng, Fang Chao, Wu Weiyue, and Wei Jing
The assembly clearance is one of the factors that affect the laser closure welding quality for international thermonuclear experimental reactor (ITER) correction coil case. An experimental study on relationship between the focused spot diameter and the butt joint gap margin in the defocusing amount of +5, +10, +16 mm rThe assembly clearance is one of the factors that affect the laser closure welding quality for international thermonuclear experimental reactor (ITER) correction coil case. An experimental study on relationship between the focused spot diameter and the butt joint gap margin in the defocusing amount of +5, +10, +16 mm respectively is performed in laser butt welding of 5 mm thick 316LN steel for nuclear fusion with hot wire filler under various butt gaps. The weld topography and cross section, metallographic phase, tensile strength, micro hardness test, electron microscope and composition of cross-section are analyzed after welding. The results show that in laser welding with hot wire filler the focused spot diameter can not be only equivalent to the butt joint gap, but also can be 0.1~0.2 mm less than the butt joint gap when the weld is of good shape and the higher tensile strength is obtained. When it is 0.3 mm less than the butt joint gap, bad weld beads are obtained and the tensile strength of the weld decreases..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1003006 (2014)
Fiber Laser Welding of 5083 Aluminum Alloy with Filler Wire
Kong Xiaofang, Li Fei, Lü Junxia, Wu Shikai, and Xiao Rongshi
5083 aluminum alloy is widely used in shipbuilding and high speed train manufacturing industry. The main problems, such as sag and undercut, occur during fiber laser welding of 5083 aluminum alloy. To overcome these problems, 5083 aluminum alloy with the thickness of 4 mm is welded using 5087 filler wire in our present5083 aluminum alloy is widely used in shipbuilding and high speed train manufacturing industry. The main problems, such as sag and undercut, occur during fiber laser welding of 5083 aluminum alloy. To overcome these problems, 5083 aluminum alloy with the thickness of 4 mm is welded using 5087 filler wire in our present work. The effects of welding parameters on the weld forming are studied in details. And the microstructure and mechanical properties of joints are also investigated. The result shows that fiber laser welding with filler wire can effectively avoid the weld surface depression and undercut defects by choosing suitable processing parameters as power of 6 kW, welding speed of 7.5 m/min, wire feed rate of 4.5 m/min, distance between laser and wire of 1.0 mm, and also gets a good joint forming with fine grain weld. The average tensile strength of the joint with filler wire is 304 MPa, about 88% of the parent material, which is also about 6.17% higher than that of the autogenous weld. The average elongation of 5.43 % with filler wire is found, which increases by 52% than that of the autogenous joint. After the transverse tensile test, the joint with filler wire is fractured along the weld, which shows the ductile characteristics..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1003007 (2014)
Study on High Cycle Fatigue Properties and Laser Shock Processing of AZ91D-T6 Cast Magnesium Alloy
Zhang Qinglai, Wu Tiedan, Qian Yang, Wang Rong, Hong Yanxin, and Chen Jun
In order to study the effect of laser shock processing (LSP) on the high cycle fatigue properties of AZ91D-T6 cast magnesium alloy, the test samples with center hole are shocked with Ndglass laser with the wavelength of 1064 nm and pulse width of 20 ns. Tensile-tensile fatigue test is also carried out on the samples. TIn order to study the effect of laser shock processing (LSP) on the high cycle fatigue properties of AZ91D-T6 cast magnesium alloy, the test samples with center hole are shocked with Ndglass laser with the wavelength of 1064 nm and pulse width of 20 ns. Tensile-tensile fatigue test is also carried out on the samples. The surface morphology, surface micro-hardness, microstructures, fatigue fracture characteristics and residual stress are analyzed. The results show that after LSP with power density of 1.5 GW/cm2 and spots of 50% overlap rate, high residual compressive stress is generated on the upper and lower surface of the fatigue samples. The micro-hardness of shocking area increases by about 24% and the grains are refined obviously. Fatigue life of the shocked samples is improved by 33.7% than that of the un-shocked samples. The Fatigue fractures show characteristics of the cleavage fracture, and the cleavage steps and river pattern are mainly observed. The crack propagation path is changed because of the existence of the β-Mg17Al12 phase. The crack initiation time is delayed after LSP, which improves the fatigue life of AZ91D-T6 cast magnesium alloy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1003008 (2014)
Fiber Laser Welding of 2060 Aluminum-Lithium Alloy with Filler Wire
An Na, Zhang Xinyi, Wang Qiming, Yang Wuxiong, and Xiao Rongshi
2060-T8 Al-Li alloy is a new aircraft material with low density, high specific strength and well properties in low temperature conditions. 2060-T8 Al-Li alloy in 2 mm thick is welded by fiber laser with 5087 (Al-Mg-Zr) filler wire. The cracking susceptibility of joints obtained under different welding parameters is inv2060-T8 Al-Li alloy is a new aircraft material with low density, high specific strength and well properties in low temperature conditions. 2060-T8 Al-Li alloy in 2 mm thick is welded by fiber laser with 5087 (Al-Mg-Zr) filler wire. The cracking susceptibility of joints obtained under different welding parameters is investigated. The microstructure and mechanical properties are analyzed as well. The result indicates that, a higher laser power or a larger welding speed causes the increase of crack number, and a lower wire feeding rate results in a higher cracking susceptibility. Under the condition of 3 kW laser power, 3 m/min welding speed and 3 m/min wire feeding rate, the weld with great formation and few welding defects are obtained. The average tensile strength of joints reaches to 309 MPa, and the tensile fractures occur in the weld zone. At the waist of weld, the fine equiaxed grains are in larger quantities and the columnar crystals are more refined than the upside and downside near the fusion line, which resultes from the mode of fluid flow in weld pool and the thickness of the boundary-layer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1003009 (2014)
Effect of Femtosecond Laser Parameters on TiC Ceramic Micro-Hole Drilling
Wang Yuqian, Zhang Junzhan, Liu Yongsheng, Yang Xiaojun, Li Weinan, and Wang Chunhui
Drilling micro-holes in TiC ceramic with femtosecond laser in different laser fluence and assisted gas pressure has been demonstrated. Scanning electron microscope (SEM), micrometer X-ray 3D imaging system (Micro-CT) and X-ray photoelectron spectroscopy (XPS) are used to investigate the morphology and chemical bonds ofDrilling micro-holes in TiC ceramic with femtosecond laser in different laser fluence and assisted gas pressure has been demonstrated. Scanning electron microscope (SEM), micrometer X-ray 3D imaging system (Micro-CT) and X-ray photoelectron spectroscopy (XPS) are used to investigate the morphology and chemical bonds of micro-holes. The results show that the circularities of micro-holes at the entry are not less than 99% when the laser fluence varies. The circularities of micro-holes at the exit increase as the laser fluence grows, then it tend to be stable. The maximum value of the circularity at the exit is 95%. The taper of micro-holes increases with the assisted gas pressure. When the laser fluence is 0.51 J/mm2, the taper of micro-holes drilled with 0.3 MPa gas pressure is the best, its long axis taper is -0.13° and the short axis taper is 0.77°. C-C bonds and Ti-C bonds rupture while debris which contains metal Ti、Ti2O3 and TiO2 forms around the micro-holes during laser drilling. Lastly, the mechanism of interactions between laser beam and materials is discussed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1003010 (2014)
Research of Lap Gap in Fiber Laser Lap Welding of Galvanized Steel
Zhang Fan, Li Fang, Wang Shien, Wang Daming, Chu Weidong, and Hua Xueming
The research on laser lap welding of galvanized steels in automobile industry is very significant. The effects of gap on the features and mechanical properties of welding seam are analyzed. Meanwhile, the impact of setting small gap between faying surfaces on suppressing defects that caused by zinc vapor is studied andThe research on laser lap welding of galvanized steels in automobile industry is very significant. The effects of gap on the features and mechanical properties of welding seam are analyzed. Meanwhile, the impact of setting small gap between faying surfaces on suppressing defects that caused by zinc vapor is studied and verified by experiments. The range of laser power and lap gap is also investigated. The outcome implies that for laser lap welding of HC260LAD+Z 100 MB galvanized steel sheet whose thickness is 1.35 mm, gaps exceeding 0.1 mm will suppress the defects caused by zinc vapor effectively. Penetration reaches the maximum value when the gap is about 0.15 mm. Greater laser power of 4 kW, has better tolerance on gap from 0.05~0.2 mm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1003011 (2014)
Two Dimensional Laser Continuous Cutting in Moving Materials′ Path Algorithm and Constraints
Hu Peng, Hu Chunyan, and Jiang Nianping
One reading micosoft office word (RW) model is presented, which is an effective way for information acquisition line by line, on top of that, the relationship of the two-dimensional laser cutting path in the two-dimensional space for the fixed size cutting of the moving materials is easily deduced. By analysing the patOne reading micosoft office word (RW) model is presented, which is an effective way for information acquisition line by line, on top of that, the relationship of the two-dimensional laser cutting path in the two-dimensional space for the fixed size cutting of the moving materials is easily deduced. By analysing the path and using the delay step function to definate algorithms about the semi-continuous, constant velocity-continuous, and variable velocity-continuous cuttings are derived. In an ideal situation, only the laser′s uniform cutting velocity parameter νy, laser′s maximum offset coordinate (x0, y0) in the two dimensional space,and the materials′ minimum cutting size LMIN is identified, the continuous-cutting model by laser can come true with regulating the laser′s moving velocity parameter ν0 and the materials′ feed rate νx in the auxiliary cutting process. Besides, for the constant velocity body, with the use of Pro/E and the analysis of the cutting efficiency in unit time, the proposed algorithm′s rationality and reliability can be easily tested, and according to the constraints analyzed in the process, two pieces of fixed size materials can be cut constantly in one unit cycle time..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1003012 (2014)
Investigation of Technical and Strengthening Mechanism Research of TiAl Alloy by Laser Shock Peening
Lu Ying, Zhao Jibin, and Qiao Hongchao
We have studied the effect of TiAl alloy shocked by the laser shock processing (LSP). When the high amplitude shock waves introduced by high energy laser exceed its dynamic yield strength, the mechanical deformation will occur in the shocked material, which will achieve the aim of surface strengthening. By changing theWe have studied the effect of TiAl alloy shocked by the laser shock processing (LSP). When the high amplitude shock waves introduced by high energy laser exceed its dynamic yield strength, the mechanical deformation will occur in the shocked material, which will achieve the aim of surface strengthening. By changing the energy of laser and peening times, we get the results of surface roughness and micro-hardness of the work-piece. The results show that with the improvement of peening times and laser energy, the surface roughness and micro-hardness are increased. The microscopic mechanism of peened materials is also investigated in this paper. Compared with un-peened ones, it can be seen that the laser shock peening can effectively improve surface of the dislocation density. When an obstruction impedes dislocation lines (DLs) motion, which will form dislocation tangles (DTs). Accumulation of dislocations is hampered by grain boundary, and forms dislocation walls (DDWs). The transformation of DTs and DDWs into sub-grain boundaries can prepare for grain refinement. The analysis of the mechanism is introduced by laser shock processing, which reveales that dislocation density is the essence of material surface mechanical properties..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1003013 (2014)
Study on High-Cycle Fatigue Behavior of Laser-Cladding Stellite6 on 17-4PH Stainless Steel
Zhao Wenyu, Lu Fenggui, Li Zhuguo, Wang Dong, Wang Xiaojuan, Liu Xia, and Yang Renjie
Stellite6 coating is cladded on the 17-4PH stainless steel using a diode laser. Fatigue behaviors of substrate specimens, as-cladded specimens and the cladded specimens with heat treatment (550 ℃ for 6 h) are tested with the tension and compression loading method. The fracture surface is characterized by scanning electStellite6 coating is cladded on the 17-4PH stainless steel using a diode laser. Fatigue behaviors of substrate specimens, as-cladded specimens and the cladded specimens with heat treatment (550 ℃ for 6 h) are tested with the tension and compression loading method. The fracture surface is characterized by scanning electron microscopy (SEM). The results show that the fatigue strength with 107 cycles of substrate specimens is 470 MPa which is higher than that of the as-cladded specimens with 380 MPa, while the fatigue strength of cladded specimens with heat treatment can reach to 440 MPa. The fatigue surface of substrate specimen shows that the fatigue crack initiates at the surface or inner defects, then propagates forward with the parallel fatigue striations and dimple appearance, while the crack of cladded specimens initiates at the defects in the coating or the interface between the coating and the substrate, then extends to the coating which shows the brittle inter-dendritic fracture and the substrate shows the ductile fatigue fracture respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1003014 (2014)
Laser Physics
Study on Space Radiation Effects of Laser Diodes Based on Poisson Process
Liu Yun, Zhao Shanghong, Yang Shengsheng, Li Yongjun, and Qiang Ruoxin
For lasers which are working in the changing state all the time, the process of single particle radiation on semiconductor laser is analysed, and space radiation effect is described as the cumulation of radiation effects caused by single particles. In consideration of the characteristic that the arrival of particles isFor lasers which are working in the changing state all the time, the process of single particle radiation on semiconductor laser is analysed, and space radiation effect is described as the cumulation of radiation effects caused by single particles. In consideration of the characteristic that the arrival of particles is a Poisson process, the performance degradation model of space irradiated semiconductor laser is established. Expressions of reliability and mean time to failure are educed. The performance degradation process of multi-quantum well semicondyctor laser in high-orbit space radiation environment is simulated using existing data, and curves of degradated optical power are obtained. Results show that degradated optical power is in direct proportion to radiating time. Therefore, taking into account of both radiation effects and annealing effect, the degenerate rate of optical power is put forward, which is in direct proportional to the average radiating dose of space radiation environment calculated by fitting. Reliability curves are achieved and the mean time to failure for device is calculated..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1002002 (2014)
Robust Gaussian Filtering of Signals for Beam-Coupling Assembly of Ring Laser Gyroscopes
Ma Li, Zhou Fujun, Xie Wei, and Liu Bo
In order to eliminate the signal noises and restrain the residual errors in the beam-coupling assembly process of ring laser gyroscopes, a robust estimation based on Gaussian filtering algorithm is presented. According to the signal characteristics in the beam-coupling assembly process, IGGIII robust estimation and eHuIn order to eliminate the signal noises and restrain the residual errors in the beam-coupling assembly process of ring laser gyroscopes, a robust estimation based on Gaussian filtering algorithm is presented. According to the signal characteristics in the beam-coupling assembly process, IGGIII robust estimation and eHuber robust estimation are used to deal with the signals. And the signal processing results between the two robust estimation methods and traditional Gaussian filtering method are compared and analyzed. By using iterative algorithm, proportion error, mean absolute error, root mean square error and signal-to-noise ratio are obtained. Experimental results show that IGGIII robust Gaussian filter can improve the robust performance of traditional Gaussian filtering and the signal errors in the beam-coupling assembly process are filtered effectively, and the signals after filtering are closest to the real signals. Therefore, the results validate the robust Gaussian filtering method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1002003 (2014)
Hundred-Watt-Level 1030 nm Ytterbium-Doped Picosecond All-Fiber LaserSun Ruoyu
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A high power 1030 nm passively mode-locked ytterbium-doped picosecond fiber laser by master oscillator power amplifier (MOPA) in all-fiber configuration is demonstrated. The laser system consists of the picosecond seed and three stages of ytterbium-doped all-fiber amplifiers. The seed is mode-locked by semiconductor saA high power 1030 nm passively mode-locked ytterbium-doped picosecond fiber laser by master oscillator power amplifier (MOPA) in all-fiber configuration is demonstrated. The laser system consists of the picosecond seed and three stages of ytterbium-doped all-fiber amplifiers. The seed is mode-locked by semiconductor saturable absorber mirror (SESAM). And a stable output is obtained with 30.7 ps pulse width, 29.0 MHz repetition rate, and 30 mW average output power. The laser operates at 1030.4 nm with a spectral width of 0.15 nm. After three stages of fiber amplification, the final output power is scaled up to 101 W in a 30 μm/250 μm double cladding ytterbium-doped fiber with the slope efficiency of 76.7%. The laser performance with the pulse width of 36.6 ps, pulse energy of 3.48 μJ, peak power as high as 97 kW operating at 1030.4 nm with bandwidth of 1.46 nm is achieved, and the beam quality M2 is 2.78..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1002004 (2014)
Generation of Partially Coherent Optical Accelerating Regular Triple-Lobe Beams and Their Optical Properties
Wu Qiong, Ren Zhijun, and Jin Hongzhen
Based on a partially coherent light source, partially coherent accelerating regular triple-lobe beams are generated by imposing phase grey-scale maps on the spatial light modulator. The numerical simulation and experimental results show that there are two key factors to decide the acceleration of the main lobes of partBased on a partially coherent light source, partially coherent accelerating regular triple-lobe beams are generated by imposing phase grey-scale maps on the spatial light modulator. The numerical simulation and experimental results show that there are two key factors to decide the acceleration of the main lobes of partially coherent optical accelerating regular triple-lobe beams, which are respectively the controlling parameter β of designed phase maps and the focal length f of Fourier transform lens. The relationship between β, f and the main lobes′ acceleration of partially coherent accelerating regular triple-lobe beams is also given. The results provide the mechanism of controlling ballistic trajectory of main lobes of partially coherent accelerating regular triple-cusp beams according to different research needs in the future..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1002005 (2014)
500 kHz, 6 ns High Repetition-Rate Electro-Optical Cavity Dumped Nd:YVO4 Laser
Shi Zhaohui, Liu Xuesong, Huang Yutao, Yan Ying, Yu Jin, and Fan Zhongwei
A high repetition-rate, short-pulse Nd:YVO4 laser based on electro-optical cavity-dumped technology is reported. This laser, end-pumped by a continuous-wave 880 nm laser diode, employs a Pockels cell made up of BBO crystal as the electro-optical Q switch. The laser resonant cavity is optimized to improve its dynamicallA high repetition-rate, short-pulse Nd:YVO4 laser based on electro-optical cavity-dumped technology is reported. This laser, end-pumped by a continuous-wave 880 nm laser diode, employs a Pockels cell made up of BBO crystal as the electro-optical Q switch. The laser resonant cavity is optimized to improve its dynamically thermal stability and the mode-matching efficiency. When the pump power is 30 W, stable 1064 nm fundamental-mode laser pulses with the maximum repetition rate of 500 kHz, pulse width of 6 ns and average power of 10 W can be achieved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1002006 (2014)
Laser-Diode-Pumped Cr4+:YAG Passively Q-Switched Intracavity PbWO4 Mode-Locked Raman Laser
Jia Haixu, Ding Shuanghong, Liu Jiajia, and Ding Ze
A laser-diode-pumped Cr4+:YAG passively Q-switched intracavity PbWO4 mode-locked Raman laser is demonstrated. Stable and Q-switched mode-locked laser output of modulation depth 100% is realized. A maximum average output power of 582 mW is obtained when the incident pump power is 6.3 W corresponding to an overall pump lA laser-diode-pumped Cr4+:YAG passively Q-switched intracavity PbWO4 mode-locked Raman laser is demonstrated. Stable and Q-switched mode-locked laser output of modulation depth 100% is realized. A maximum average output power of 582 mW is obtained when the incident pump power is 6.3 W corresponding to an overall pump light-first-order Stokes conversion efficiency of 9.24% and a slope efficiency of 10.6%. The Q-switched pulse with repetition rate of 41.3 kHz and pulse width of 6 ns is obtained. The width of the mode-locked pulse is estimated to be less than 207 ps with 1.1 GHz the repetition rate of 1.1 GHz..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1002007 (2014)
Materials and Thin Films
Near-Infrared Spectroscopic Properties and Judd-Ofelt Theory Analysis of Er3+/Yb3+ Co-Doped Fluoride Particles
[in Chinese]
Er3+/Yb3+ ion co-doped fluoride particles are synthesized and analyzed by their absorption spectra. The influence of the substances, the calcination temperature, and the doping ratio of Er3+ and Yb3+ on the absorption of the synthesized materials are studied. By analyzing the spectra of the samples with the Judd-Ofelt Er3+/Yb3+ ion co-doped fluoride particles are synthesized and analyzed by their absorption spectra. The influence of the substances, the calcination temperature, and the doping ratio of Er3+ and Yb3+ on the absorption of the synthesized materials are studied. By analyzing the spectra of the samples with the Judd-Ofelt (J-O) theory, the intensity parameters are obtained as Ω2=9.9887, Ω4=2.7333, Ω6=0.4868, respectively. The results show that the phonon assisted transition probability and the energy transfer efficiency increases after heat treatment of the samples. The best doping ratio of Er3+ and Yb3+ is 16. Analysis based on the Judd-Ofelt theory shows that the synthesized fluoride particles have low phonon energy and good absorption property in the near-infrared region after doping with Er3+ and Yb3+ ions. It can be used as a kind of good materials for near-infrared upconversion..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1006002 (2014)
Design of Phase-Shifted Rugate Thin Film Spatial Filter
Zhang Ying, Yi Kui, Qi Hongji, and Shao Jianda
The basic structure and principles of phase-shift Rugate thin spatial filter is presented. The phase-shifted Rugate film filter is designed and the error analysis is prepared in accordance with the actual conditions. The corresponding loss and extinction coefficient and the preparation of technical precision are discusThe basic structure and principles of phase-shift Rugate thin spatial filter is presented. The phase-shifted Rugate film filter is designed and the error analysis is prepared in accordance with the actual conditions. The corresponding loss and extinction coefficient and the preparation of technical precision are discussed to achieve excellent performance for the preparation of the thin film. The corresponding loss and internal electric field of the phase-shift Rugate film filter is calculated..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1007001 (2014)
Optical Communication
Research of All-Fiber Laser Coherent Combining System Based on Fiber-Loop
Yang Baolai, Wang Xiaolin, Zhou Pu, Ji Xiang, and Xu Xiaojun
A scheme of all-fiber laser coherent combining system based on fiber-loop is put forward and passive coherent combining of four fiber laser beams is realized in all-fiber configuration with home-made fiber amplifiers. The power, spectrum and far-field beam pattern of the combined open loop and closed loop as well as thA scheme of all-fiber laser coherent combining system based on fiber-loop is put forward and passive coherent combining of four fiber laser beams is realized in all-fiber configuration with home-made fiber amplifiers. The power, spectrum and far-field beam pattern of the combined open loop and closed loop as well as the bandwidth of passive phasing are also investigated. When the system is in open loop, the output power varies from 71 mW to 271 mW. When the system is in closed loop, the output power is around 412 mW. The output power with system in closed-loop state is quite stable, and 2.1 times higher than the average output power in open-loop state, indicating that the scheme can realize stable phase locking. The bandwidth of the system is over 50 kHz, implying good ability of passive phasing. By improving the power of the amplifiers and adopting combiners with higher handling power, it is possible to obtain coherent combining output with higher power..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1005001 (2014)
Experimental Study on Suppression of Stimulated Brillouin Scattering in 2 μm-Band Fiber Laser Based on Phase Modulation
Wu Weijun, Wang Xiong, Xiao Hu, and Zhou Pu
Experiments are conducted based on phase modulation in order to research the suppression on stimulated Brillonin scattering (SBS) effect at different modulation frequencies and voltages. A 0.17 nm Stokes frequency shift without phase modulation is observed, and the corresponding SBS threshold is about 120 mW. The phaseExperiments are conducted based on phase modulation in order to research the suppression on stimulated Brillonin scattering (SBS) effect at different modulation frequencies and voltages. A 0.17 nm Stokes frequency shift without phase modulation is observed, and the corresponding SBS threshold is about 120 mW. The phase modulation is realized by an electro-optic modulator whose half-wave voltage is 3.5 V. When the modulation voltage is 4 V and the frequencies are 1 MHz and 5 MHz, respectively, and the SBS threshold power is 250 mW and 440 mW. When the modulation frequency increases, the threshold power continuously increases. When the modulation frequency is higher than 30 MHz, the SBS effect is not observed below the damage limited power..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1005002 (2014)
Investigation on Random Error Properties of Optic Gyroscope Based on Theoretical Variance #1
Cheng Xuwei, Tang Xiaqing, and Huang Xiangyuan
In order to solve the problems that the averaging time of Allan variance can only reach half of total data length, and confidence at long averaging time is lower, according to the random errors properties of the optic gyroscope at time and frequency domains, a new method for analyzing the random error properties of theIn order to solve the problems that the averaging time of Allan variance can only reach half of total data length, and confidence at long averaging time is lower, according to the random errors properties of the optic gyroscope at time and frequency domains, a new method for analyzing the random error properties of the optic gyroscope based on theoretical variance #1 is proposed. By comparing the performance of the Allan and theoretical variance #1, identifying the noise types and noise levels, applying Allan variance and theoretical variance #1 methods, it is shown that the values of the theoretical variance #1 are consistent with the power law noises in estimating long-term τ-values, which improves the confidence efficiently and has higher evaluation precision than the conventional Allan method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1005003 (2014)
Low Loss Fusion Splicing for Seven-Core Photonic Crystal Fiber by Selected Air Hole Collapse Technique
Zhang Chengdong, Zhou Xuanfeng, Chen Zilun, and Xu Xiaojun
The muti-core photonic crystal fibers (MCPCF) is one major research direction to realize high power supercontinuum, and a key problem to realize all-fiber is how to solve the low loss fusion splicing for MCPCF. One method to realize low loss fusion splicing for seven-core PCF by selected air hole collapse technique is The muti-core photonic crystal fibers (MCPCF) is one major research direction to realize high power supercontinuum, and a key problem to realize all-fiber is how to solve the low loss fusion splicing for MCPCF. One method to realize low loss fusion splicing for seven-core PCF by selected air hole collapse technique is introduced. Mode field property and its effect on splicing loss both before and after process are numerically simulated. Selected air hole collapse is achieved for a seven-core PCF experimentally and a low loss (0.22 dB) is realized for splicing to a double cladding fiber with core diameter of 15 μm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1005004 (2014)
Research on Preparation of Quasi-Phase-Matched GaAs and Pulsed CO2 Laser Frequency Doubling
Wang Hao, Hui Yongling, Jiang Menghua, Lei Hong, Li Qiang, Huang Wei, Zheng Yijun, and Tan Rongqing
A diffusion bonding method of quasi-phase-matched (QPM)-GaAs crystal preparation is studied. By ultra-high vacuum pre-bonding-high temperature annealing method, the preparation of three quasi-phase-matched crystals is completed under different load pressures. The polarization period length of the QPM structure is 219 μA diffusion bonding method of quasi-phase-matched (QPM)-GaAs crystal preparation is studied. By ultra-high vacuum pre-bonding-high temperature annealing method, the preparation of three quasi-phase-matched crystals is completed under different load pressures. The polarization period length of the QPM structure is 219 μm, number of layers is 44, the diameter is 18 mm, and the effective aperture is 15 mm. The best transmittance of the foundation and frequency doubling is above 30% without anti-reflection coating. Using transversely excited atmospheric pressure (TEA)-CO2 laser with 90 ns wide main pulse and 2~6 μs wide tailing as foundation source, we acquire second harmonic generaction (SHG) output with efficiency more than 4% on 4.63~5.37 μm waveband by tuning foundation wavelength. When the foundation wavelength is 10.68 μm, main pulse energy is 409 mJ, the density in QPM-GaAs is 3.65 MW/cm2, we get SHG output with 26.9 mJ pulse energy, 298 kW peak power, and the SHG efficiency of 6.58%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1006001 (2014)
Study on Time Evolution Process of Laser-Induced Aluminum Alloy Plasma
Zheng Peichao, Liu Hongdi, Wang Jinmei, Yu Bin, Yang Rui, Zhang Bin, and Wang Xiaomeng
In order to further investigate the physical properties of the laser-induced plasma and improve the measurement precision and reliability of the laser-induced breakdown spectroscopy (LIBS) technology, the time evolution process of the laser-induced plasma is studied experimentally. Through fast imaging of the laser-indIn order to further investigate the physical properties of the laser-induced plasma and improve the measurement precision and reliability of the laser-induced breakdown spectroscopy (LIBS) technology, the time evolution process of the laser-induced plasma is studied experimentally. Through fast imaging of the laser-induced aluminum alloy plasma using the ICCD camera, it is found that the lifetime of the laser-induced aluminum alloy plasma is about 30 μs, the plasma has an obvious hierarchical structure, and furthermore the areas and temperatures of different regions present different characteristics during the time evolution process. The time evolution process laws of the electron temperature and the electron number density are obtained using the Boltzmann plot method and Stark broadening of line, respectively. The results show that the electron excitation temperature of the plasma ranges from 6000 K to 9000 K, and it decreases rapidly in the first 3 μs. Besides the electron number density is in the order of 1017 cm-3, it decreases slowly with ICCD detection delay time. The time evolution laws of electron temperature and the electron number density are in agreement with that of the fast imaging by the ICCD camera..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1015001 (2014)
Terahertz Technology
Passive Terahertz Image Restoration Based on Markov Constraint
Sun Xiao, Zhao Yuanmeng, Deng Chao, Zhang Cunlin, and Zhao Yuejin
Terahertz (THz) wave is suitable for human body security imaging because of the unique characteristics of THz wave. But the signal noise ratio, constrast and resolution of original terahertz images need to be improved presently. In order to improve the quality of the THz images for security screening, a passive THz imaTerahertz (THz) wave is suitable for human body security imaging because of the unique characteristics of THz wave. But the signal noise ratio, constrast and resolution of original terahertz images need to be improved presently. In order to improve the quality of the THz images for security screening, a passive THz imaging restoration algorithm based on Markov random field is put forward. After being pre-processed by image de-noising and enhancement treatments, the original image is restored based on Bayes analysis to which Markov constraint is added. Different definition of resulting images are obtained by changing iteration and regularization parameter. Optimum parameters are determined by objective standard evaluation and subjective visual effect. Experimental results show that the proposed method achieves good balance between noise removing and edge information preserving of passive terahertz image. Thus target resolving ability of terahertz security images is improved dramatically..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1011001 (2014)
Geometric Optics
Differential Confocal Microscopy for Edge Contour Detection and Location
Liu Dali, Wang Yun, Qiu Lirong, and Zhao Weiqian
In order to realize high-efficiency and high-accuracy edge contours detection and location for micro structures such as photolithographic mask, a differential confocal microscopy (DCM) for edge contour detection and location is proposed and verified by simulation analysis and experiments. The proposed method has an axiIn order to realize high-efficiency and high-accuracy edge contours detection and location for micro structures such as photolithographic mask, a differential confocal microscopy (DCM) for edge contour detection and location is proposed and verified by simulation analysis and experiments. The proposed method has an axial response characteristic of zero-cross step trigger at focal point. Utilizing the step trigger characteristic, the proposed method can realize the real-time sample edge contour imaging in the form of binary image, and greatly improve the efficiency of edge contour detection. Theoretical analysis and computer simulations show that the proposed method can precisely detect and locate the edge contour without being affected by edge shape and direction, and has the ability of suppressing the interference caused by multiplicative and additive noise. Experimental results indicate that period measurement difference of 5 μm-period atomic force microscope standard step between the proposed method and atomic force microscope is only 2 nm. So the proposed method can be used for the real time, precise and rapid industrial edge contour inspection for microstructures..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1008001 (2014)
Acceleration Aging of InGaAs PIN Photoelectric Detectors
Jin Lufan, Zhang Yating, Wang Haiyan, Wang Maorong, Song Xiaoxian, and Yao Jianquan
The InGaAs PIN photoelectric detector has great value in fields of spatial remote sensing and satellite communication .Evolvement rules of the output electrical signal noise are studied with the experiment of acceleration aging at constant temperature 358 K when the detector operates stablly in a long term. And on thisThe InGaAs PIN photoelectric detector has great value in fields of spatial remote sensing and satellite communication .Evolvement rules of the output electrical signal noise are studied with the experiment of acceleration aging at constant temperature 358 K when the detector operates stablly in a long term. And on this basis,failure analysis of the detector working in long-term is discussed by comparison with the fore-and-aft linear region and temperature property of its noise. The theoretical results indicate that after operating stablly in about 10.8 years,thermal noise of the detector′s background noise will increase about 20%,and dark current noise about 0.35%. For the linear region of two detectors 13.31% and 9.95% are declined. Furthermore,the output noise model is modificated according to the analysis and the results of the experiments..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1008002 (2014)
Measurement of a Single Coal Particle in an Acoustic Levitation Field by Digital Holography
Zhao Huafeng, Wu Xuecheng, Zhou Binwu, Xue Zhiliang, Chen Linghong, Qiu Kunzan, and Cen Kefa
The phenomena of a single coal particle in an acoustic levitation field both cold and hot state are investigated by digital holography. Particle size and three-dimensional location of the same coal particle both cold and hot state are obtained using wavelet transformation for the reconstruction of holograms recorded byThe phenomena of a single coal particle in an acoustic levitation field both cold and hot state are investigated by digital holography. Particle size and three-dimensional location of the same coal particle both cold and hot state are obtained using wavelet transformation for the reconstruction of holograms recorded by charge coupled device (CCD). The key point is to analyze the phenomenon of volatile release and particle breakage of coal particle irradiated by CO2 laser. Results show that the volatile separates out only in the vertical direction, especially in sharp corners. And the pieces after being broken apart differed in both dimensions and position, particularly distance in z axis. The combustion rate of heated particle is computed through particle size change over time. In addition, the z position change over time of heated particle is presented. The experimental results indicate that digital holography is a feasible tool for the measurement of flaming coal particles in acoustic levitation field. It is proved to be a powerful method for researching the combustion characteristics of coal particle..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1008003 (2014)
Optical Design and Fabrication
Optical Design of Target Range UV Telescope System
Li Bo
Ultraviolet (UV) spectrum is an important method for photoelectric measurement. Ultraviolet target signal is weak, only a few kinds of optical materials in this spectral range can be chosen, so it′s difficult for the high-resolution ultraviolet observations. A large relative aperture and long-focus UV optical system isUltraviolet (UV) spectrum is an important method for photoelectric measurement. Ultraviolet target signal is weak, only a few kinds of optical materials in this spectral range can be chosen, so it′s difficult for the high-resolution ultraviolet observations. A large relative aperture and long-focus UV optical system is designed which is used in target range measurement, and it solves those problems by catadioptric imaging and reimaging. The UV optical system has the parameters of F number of 2, focal length of 400 mm, field of view (FOV) of 1°, wavelength range of 250~400 nm. The Nyquist frequency (38 lp/mm) modulation transfer function (MTF) is better than 0.7 in the telescope system FOV according to the analysis of optical software. Taking into account the environmental adaptability, focusing amount and image quality are considered at -40 ℃~60 ℃ for the UV telescope system. Result shows that the Nyquist frequency MTF is better than 0.5 after focusing which meets the design specifications and the practical application..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1016001 (2014)
Optical Design of “Cell Factory” Microscopic Monitoring Device
Li Qi, Xiang Yang, Gu Junda, and Dong Meng
Due to the limitation of observation method in cell factory (1~40 layer dishes) monitoring in China, this paper designs a long-working-distance video objective for observing the cultured cells in cell factory, to facilitate the observation, save time and improve efficiency. According to the size of cells, the high resoDue to the limitation of observation method in cell factory (1~40 layer dishes) monitoring in China, this paper designs a long-working-distance video objective for observing the cultured cells in cell factory, to facilitate the observation, save time and improve efficiency. According to the size of cells, the high resolution video objective, with 5 times magnification and 85 mm working distance, is designed by applying ZEMAX stimulation and Cassegrain reflector system. Amplified again by the video display, the total magnification is about 200 times, the numerical aperture is up to 0.3 and the liner field object height y is 0.6 mm, equipped with MV-200UC 1/3″ charge couple device (CCD) produced by Microvision in observation. The minimum distance resolution of the system is about 1.1 μm, meeting the requirement of distinguishing petri dish cells..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1016002 (2014)
Compact Laser Direct Writing System
Hu Yonglu, Xu Wendong, Wang Chuang, Zhao Chengqiang, Liu Tao, and Liu Yang
As the early developed laser direct writing device has low writing speed and its function is not perfect, a new compact system is designed and constructed. A 405 nm high-speed analog modulated semiconductor laser is used as the light source to make the structure more compact; the movement of the nano platform is adjustAs the early developed laser direct writing device has low writing speed and its function is not perfect, a new compact system is designed and constructed. A 405 nm high-speed analog modulated semiconductor laser is used as the light source to make the structure more compact; the movement of the nano platform is adjusted to sinusoidal oscillating mode to increase writing speed; functions such as writing power calibration, sample observation based on complementary meta-oxide-semiconductor transistor (CMOS), blue light confocal imaging and ordinary photoresist writing are added. By recording focus date, writing light, auxiliary focusing light and sample observing light can work separately and will not interfere with each other. Experiments show that the system can plot or pattern vector and scalar graphics on arbitrary photosensitive films. It takes at least 100 s to finish writing 200 μm×200 μm writing area with writing feature size smaller than 250 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1016003 (2014)
Remote Sensing and Sensors
An Empirical Mode Decomposition Algorithm Based on Cross Validation and Its Application to Lidar Return Signal De-Noising
Wang Huanxue, Liu Jianguo, Zhang Tianshu, and Dong Yunsheng
Noise reduction method of lidar atmospheric backscattering signal based on empirical mode decomposition (EMD) is developed by Cross-Validation. Considering characteristics of lidar return signal noise and defects of traditional de-noising algorithm, Cross-Validation is applied to identify signal layers and noise layersNoise reduction method of lidar atmospheric backscattering signal based on empirical mode decomposition (EMD) is developed by Cross-Validation. Considering characteristics of lidar return signal noise and defects of traditional de-noising algorithm, Cross-Validation is applied to identify signal layers and noise layers automatically, and then separate signal and noise by EMD reconstruction. With experiments, the method can select the signal in the instrinsic mode function adaptively, not only removes the random error, but also maintains the effective characteristics of the signal, reduces the loss of signal, and then improve the accuracy in the next phase of data processing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1014001 (2014)
High Throughput Detection Based on Surface Defect Photonic Crystal with Absorbing Medium
Chen Ying, Lu Bo, and Fan Huiqing
A surface defect photonic crystal with absorbing medium is proposed to achieve the high throughput detection of sample solution information combining the surface wave resonance theory and microwell plate technique. According to the layered transmission matrix method and the Goos-Hnchen theory, the refractive index senA surface defect photonic crystal with absorbing medium is proposed to achieve the high throughput detection of sample solution information combining the surface wave resonance theory and microwell plate technique. According to the layered transmission matrix method and the Goos-Hnchen theory, the refractive index sensing mechanism is analyzed and the theoretical model between the resonance angle and the refractive index change of the detected sample is proposed. Combining the microwell plate technique and the angle modulation method, the spectrum analysis for different detected samples in different sensing areas can be performed respectively in the same scanning period. The simulation results show that the change of the concentration for the detected sample can vary the resonant angle, which makes the shift of the resonant defect peak wavelength in the reflective spectrum. In addition, the simultaneous detection of multiple sample resolution information can be obtained by angle scanning in single period. The method can provide certain theoretical and technical references for the design of high throughput detection system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1014002 (2014)
Temporal and Spatial Distribution Characteristics of Ozone Based on Differential Absorption Lidar in Beijing
Fan Guangqiang, Zhang Tianshu, Fu Yibin, Dong Yunsheng, Chen Zhenyi, Liu Jianguo, and Liu Wenqing
The differential absorption lidar is an effective tool for measuring ozone distributions. In the haze event, the differential absorption lidar is carried out to observe the temporal and spatial distribution characteristics of ozone concentration. The results show that a high ozone pollution process is caused by southweThe differential absorption lidar is an effective tool for measuring ozone distributions. In the haze event, the differential absorption lidar is carried out to observe the temporal and spatial distribution characteristics of ozone concentration. The results show that a high ozone pollution process is caused by southwest airflow together with the influence of subtropical anticyclone in mid June. From the night of June 14 to midday of June 15, ozone concentration in high altitude reaches above 1.2×10-7. And the ozone gas ranging from 1.5 km to 2 km moves down to the surface, thus causing the increase of surface ozone concentration afternoon on June 15. In the haze period, the distributions of fine particulates and ozone show different characteristics in different heights. Specifically the near-ground particles completely participate in the photochemical reaction process, while particles and ozone with are more related to transportation. In addition ozone concentration in clear weather is low and no obvious external input air mass is observed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1014003 (2014)
Application of Three-Dimensional Laser Radar to the Measurement of Deviation Angle of Guns
Li Danni, Hu Dan, Wang Jinsong, Zhang Jiming, and An Zhiyong
Aiming at such problems as low accuracy, low efficiency, more operators and disperse structure existing in the measurement of deviation angle of guns using the method in the national military standard, a novel method for the measurement of gun deviation angles is proposed. Based on the principle of measuring three-dimeAiming at such problems as low accuracy, low efficiency, more operators and disperse structure existing in the measurement of deviation angle of guns using the method in the national military standard, a novel method for the measurement of gun deviation angles is proposed. Based on the principle of measuring three-dimensional (3D) coordinates of a spatial point by the 3D laser radar, standard target balls adhering to the gun barrel are used to solve two spatial linear equations before and after gun adjusting through measuring the spherical coordinates of spatial points of standard target balls. After the projection of space vectors, the equations are transformed to solution of linear equations on the projection plane, thus the gun deviation angle is calculated, and the measurement accuracy is calculated and analyzed by differentiation. The principle and measurement process of the method is compared to that in the national military standard, and the experimental data show that the efficiency and accuracy is improved notably when the proposed method is adopted to measure the gun deviation angle..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 10, 1014004 (2014)
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