Journals >Chinese Journal of Lasers
Contents
2014
Volume: 41 Issue 6
49 Article(s)
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[in Chinese]
Enhanced Output Power of InGaN Superluminescent Diode Using Active Multi-Mode Interferometer
Zang Zhigang, Yu Jianhui, Zhang Jun, and Chen Zhe
To improve the output power of InGaN superluminescent diodes (SLED), an active multimode-interferometer (Active-MMI) configuration has been used to fabricate the Active-MMI SLED. Because of the wider actively pumped area, the output power saturation level has been improved. The experiment results show that the maximum To improve the output power of InGaN superluminescent diodes (SLED), an active multimode-interferometer (Active-MMI) configuration has been used to fabricate the Active-MMI SLED. Because of the wider actively pumped area, the output power saturation level has been improved. The experiment results show that the maximum output power of Active-MMI SLED as high as 47 mW is obtained with a wide 3 dB bandwidth of 20 nm and flat spectrum. Moreover, even under the maximum output power of Active-MMI SLED, it still keeps a stable single mode output..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 617001 (2014)
Research Article
Effects of Etch Holes on Optical Properties of Micro Electro Mechanical System Deformable Mirror
Cai Dongmei, Ti Peipei, Jia Peng, and Wang Dong
Micro electro mechanical system (MEMS) deformable mirrors fabricated by surface technics have the advantages of small volume, high resolution and low driving voltage et al.. However a large number of etch holes on the mirror formed in a regular array structure affect the optical properties of the deformable mirror (DM)Micro electro mechanical system (MEMS) deformable mirrors fabricated by surface technics have the advantages of small volume, high resolution and low driving voltage et al.. However a large number of etch holes on the mirror formed in a regular array structure affect the optical properties of the deformable mirror (DM). We design and manufacture MEMS DM cell based on surface technics, which can be used in the research of effects of etch holes on optical properties of DMs. From the Fraunhofer diffraction theory, diffraction patterns created by two-dimensional etch hole arrays on MEMS DMs have been investigated. Research result shows that when the dimensions of etch holes increase and adjacent spacings of etch holes decrease, the central zero-order diffracted light intensity decreases and the diffraction effect increases, leading to decreases of the effective reflection surface and reflectivity of DM surface. The etch hole structures affect measurement performance of Shark-Hartmann wavefornt sensor on wavefront aberration. Because they can reduce the energy of focal spot and reduce the accuracy of wavefornt measurement with the disturbance of wavefornt enhanced and focused spot adjacent crosstalk..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 612001 (2014)
Investigation of Anisoplanatic Effect in Atmospheric Turbulence Probing with Beacon INumerical Modeling
Luo Xi, and Li Xinyang
The atmospheric turbulence probing source of adaptive optics (AO) is proposed by the promotion of beacon (namely guide star, GS). However the unavoidable anisoplanatic error it brings can degrade the performance of AO system. Taking account of the differences of height location and spatial angular deviations between GSThe atmospheric turbulence probing source of adaptive optics (AO) is proposed by the promotion of beacon (namely guide star, GS). However the unavoidable anisoplanatic error it brings can degrade the performance of AO system. Taking account of the differences of height location and spatial angular deviations between GS and object, the ensemble statistical characteristics of anisoplanatic error with different GS modes are investigated by numerical modeling, including natural guide star (NGS) and laser guide star (LGS). In NGS mode, the effective angular anisoplanatic variance is smaller than the traditional evaluation value (θ/θ0)5/3. So the conventional characterization of the angular anisoplanatic degradation in AO correction with atmospheric anisoplanatic angle θ0 is more serious than actual circumstance. In LGS mode, the higher the beacon probing altitude is, the smaller the Zernike aberration modal anisoplanatic error is. But the aberration modal correlation degradation between LGS and object resulted from their angular deviation becomes more sensitive. Under such circumstance the AO system operation mode and the GS mode should be weighed up and optimized according to practical application. The numerical results provide theoretical support for the experiment investigation of atmospheric AO with LGS in future..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 612002 (2014)
Investigation of Anisoplanatic Effect in Atmospheric Turbulence Probing with Beacon IIExperimental Measurement
Luo Xi, Li Xinyang, Shao Li, Huang Kui, and Wang Xiaoyun
The atmospheric turbulence probing source of adaptive optics (AO) is proposed by the promotion of the artificial beacon, namely laser guide star (LGS); however the unavoidable anisoplanatic error it brings can degrade the performance of AO system. By using new developed natural star Hartmann-Shack (HS) sensor and artifThe atmospheric turbulence probing source of adaptive optics (AO) is proposed by the promotion of the artificial beacon, namely laser guide star (LGS); however the unavoidable anisoplanatic error it brings can degrade the performance of AO system. By using new developed natural star Hartmann-Shack (HS) sensor and artificial beacon HS sensor, the temporal synchronized turbulence-induced wavefronts measurement is achieved on telescope system for natural star and Rayleigh-LGS. Accordingly our experimental investigation of Rayleigh-LGS anisoplanatism effect with different LGS-modes (including focal anisoplanatism and angular & focal anisoplanatism) is presented. The experimental results show that, increasing the Zernike order of turbulence-distorted wavefront aberration makes the temporal correlation for corresponding aberration mode between natural star and Rayleigh-LGS with different altitudes present an oscillation downward trend. Comparing with the Zernike variances of natural star wavefront, the modal anisoplanatic error of Rayleigh-LGS increases with the increase of the Zernike order, which is greatly sensitive to high-order aberration. At last the comparisons of our former numerical-modeling and experimental-measuring results of different-mode Rayleigh-LGS anisoplanatic error′s impact on the corrected light-wave quality are analyzed, and both of the results are in good agreement. This investigation is a useful promotion of our perceptive knowledge of Rayleigh-LGS anisoplanatic effect in turbulence probing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 612003 (2014)
Numerical Simulation of the Number of Return Photons from Sodium Laser Beacons Excited by Macro-Micropulse Laser
Liu Xiangyuan, Qian Xianmei, Huang Honghua, Li Yujie, and Rao Ruizhong
The macro-micropulse laser with broadband and circular polarization can effectively excite the sodium atoms in the mesosphere, which can offer more return photons for the wave-front sensing of the adaptive optics. Based on the two-level Bloch equation, considering the distribution of laser intensity under the differentThe macro-micropulse laser with broadband and circular polarization can effectively excite the sodium atoms in the mesosphere, which can offer more return photons for the wave-front sensing of the adaptive optics. Based on the two-level Bloch equation, considering the distribution of laser intensity under the different models for atmosphere turbulence in the mesosphere, the number of return photons for sodium laser beacons is calculated under the three models for atmospheric turbulence by the method of numerical simulation. Then, the scale of atmosphere coherent length is conjectured according to experience and the average value for the number of return photons is calculated. The average value is relatively close to the experimental values. Because the effects of the recoil, down-pumping and geomagnetic field can be neglected, the return photons can be computed by the effective absorption cross-section. However, this method leads to the smaller results of computation because there is no consideration of the influence of laser polarization, beam quality factor and intensity distribution on the probability of excited states..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 613001 (2014)
Holography and Information Processing
Phase Retrieval Algorithm Combining Transport of Intensity Equation and Angular Spectrum Iterative
Cheng Hong, Shen Chuan, Zhang Cheng, Zhang Fen, and Wei Sui
Phase retrieval technology combines optics and calculations to recover phase from the intensity measurement, including transport of intensity equation and angular spectrum iterative. Unfortunately, the former is only effective for near-field phase retrieval, and it can not be directly applied to the phase retrieval of Phase retrieval technology combines optics and calculations to recover phase from the intensity measurement, including transport of intensity equation and angular spectrum iterative. Unfortunately, the former is only effective for near-field phase retrieval, and it can not be directly applied to the phase retrieval of natural scenes, because this method is based on the assumption of coherent illumination. The latter has many shortcomings including iterative uncertainty, slow convergence and so on. Traditional transport of intensity equation combining with angular spectrum iterative is explored in the case of coherent illumination. The fusion method is further expanded and the phase retrieval method is proposed for natural scene lens model. The phase of the image plane is calculated using transport of intensity equation, and the value is used as the initial value of the angular spectrum iterative. The phase information in the object plane is acquired according to the reversibility of the optical path. The results of experiments are given in these two cases..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 609001 (2014)
Computer Generated Hologram of Complex Three-Dimensional Object Based on a Two-Dimensional Color Image and the Depth Map
Cao Xuemei, Sang Xinzhu, Chen Zhidong, Leng Junmin, Zhang Ming, Guo Nan, Yu Chongxiu, and Xu Daxiong
The computer generated Fresnel hologram of a complex three-dimensional (3D) object is synthesized based on a two-dimensional (2D) color image and a stereo matched depth map. The intensity of the color image is divided into multiple slices based on the depth map. The depth value of each slice is transformed into the disThe computer generated Fresnel hologram of a complex three-dimensional (3D) object is synthesized based on a two-dimensional (2D) color image and a stereo matched depth map. The intensity of the color image is divided into multiple slices based on the depth map. The depth value of each slice is transformed into the distance of Fresnel diffraction. According to the principle of tomography, the hologram of the whole 3D scene can be achieved with the single step Fresnel diffraction method. The results show that the method can record and reconstruct the complex 3D object correctly. Intensity superposition method is used to suppress the speckle noise in the reconstructed images, which improves the representation quality significantly..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 609002 (2014)
Application of Three-Dimensional Depth Image in Automatic Statistic Passenger Flow System
Yin Zhangqin, Gu Guohua, Chen Qian, and Qian Weixian
A new method of detecting passenger flow based on human head and shoulder three-dimensional information is proposed, detecting passenger flow according to spatial relationship features between head and shoulders as well as head shape, size and other characteristics, which can effectively solve system overall performancA new method of detecting passenger flow based on human head and shoulder three-dimensional information is proposed, detecting passenger flow according to spatial relationship features between head and shoulders as well as head shape, size and other characteristics, which can effectively solve system overall performance reduce problems owing to ordinary color-camera image processing being affected by light, posture, shelter and so on. With Xtion sensor as a platform, identifing and tracking human head, counting the passenger flow according to comprehensive analysis on depth image of body surface three-dimensional features. The experimental results show that this method not only improves the precision and efficiency of detection,reducing the amount of computation of data, real-time video stream can be processed, but also solves the need to establish training detection in color images. The system accuracy can be up to 96%, and has practical value..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 609003 (2014)
Dynamic Assessment of Laser-Dazzling Effects Based on the Character of Laser-Spot and Image Feature
Qian Fang, Sun Tao, Guo Jin, and Wang Tingfeng
Laser active imaging systems are usually used in important region surveillance and dangerous target identification. However, the photoelectric imaging detector in the imaging systems is easy to be disturbed from opponents and this leads to errors of the recognition. In practice, the laser power and the spot position chLaser active imaging systems are usually used in important region surveillance and dangerous target identification. However, the photoelectric imaging detector in the imaging systems is easy to be disturbed from opponents and this leads to errors of the recognition. In practice, the laser power and the spot position change momentarily and this leads to different laser-dazzling effects in every frame. Therefore, dynamic assessments of laser-dazzling effects must be better understood. A new no-reference dynamic feature metric (DFM) assessment algorithm based on the character of the laser spot and image feature is proposed. The features from accelerated segment test (FAST) algorithm is used to extract feature points of the target image and disturbed image. The target area is obtained via feature-point matching, and the characteristic of the laser spot reflects the image quality through the saturated pixel number and spot position in the target area. After that, the distribution of the feature points, edges and edge definition reflect the varieties of the image feature. The normalized DFM is obtained via product of the five factors above. The luminance imaging experiment is performed for the targets by utilizing the laser active imaging system. In the experiment, the disturbed images of different disturbing powers and different spot positions are obtained. The proposed DFM algorithm is used to evaluate the newly obtained laser-dazzling images, and the results show that the DFM gives a more reasonable evaluation result for different laser-dazzling images. The evaluation results reflect the invalidation of the target identification algorithm objectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 609004 (2014)
Optical System Design of Shelter Holographic Sight
Zhang Yuanying, Ren Xuechang, Lu Qinghong, Liu Jiazhou, and Liu Shou
Based on the optical system of compact matching holographic sight, a novel shelter holographic sight is proposed. The core of this equipment includes two parts. One part is the diffraction matching holographic optical elements, the other is the corner-turning optical auxiliary system. The holographic sight theory, the Based on the optical system of compact matching holographic sight, a novel shelter holographic sight is proposed. The core of this equipment includes two parts. One part is the diffraction matching holographic optical elements, the other is the corner-turning optical auxiliary system. The holographic sight theory, the designing plan and the manufacturing method are introduced. Meanwhile, experiments and analysis on this system show that this optical system satisfies the corner shooting function without exposure..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 609005 (2014)
A Method of Dot-Matrix Holography Based on the Diffraction Grating and Spatial Light Modulator
Hu Jin, Pu Donglin, Wei Guojun, and Chen Linsen
The working principle of the modern dot-matrix hologram lithography systems is discussed. A novel optical scheme based on the diffraction grating and high performance spatial light modulator——digital micro-mirror device (DMD) is proposed. Based on the optical scheme, a flash-on-fly working mode is realized. A much highThe working principle of the modern dot-matrix hologram lithography systems is discussed. A novel optical scheme based on the diffraction grating and high performance spatial light modulator——digital micro-mirror device (DMD) is proposed. Based on the optical scheme, a flash-on-fly working mode is realized. A much higher manufacturing efficiency and positioning precision is obtained compared with the traditional step-and-repeat working mode. The main influencing factors of the optical resolution, imaging quality and depth of focus are discussed based on the frequency domain analysis. The implementation of the flash-on-fly exposure mode is illustrated at the end..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 609006 (2014)
Laser Devices and Laser Physics
Development of Digital Holography in Particle Field Measurement
Wu Yingchun, Wu Xuecheng, and Cen Kefa
Small particles widely exist in nature, which are applied to various industrial productions. The three-dimensional (3D) characteristics of particles with digital holography play key roles in scientific researches and applications. Digital particle holography and its applications have been systematically surveyed. The fSmall particles widely exist in nature, which are applied to various industrial productions. The three-dimensional (3D) characteristics of particles with digital holography play key roles in scientific researches and applications. Digital particle holography and its applications have been systematically surveyed. The formation of particle holography based on light scattering theories and diffraction theories and its fringe patterns are introduced. Holograms processing algorithms including numerical reconstruction, particle detecting, 3D position locating and particle pairing are presented. Typical applications of digital holography to particle field measurement including particle size, shape, 3D position and 3D velocity are demonstrated. Digital holography, as a 3D measurement tool, shows great potential in particle field characterization..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 601001 (2014)
Laser Manufacturing
Research on Process and Property of CoCrMo Alloy Directly Manufactured by Selective Laser Melting
Song Changhui, Yang Yongqiang, Wang Yunda, Yu Jiakuo, and Mai Shuzhen
The process of selective laser melting (SLM) direct manufacturing based on CoCrMo alloy is studied to explore the optimized process of CoCrMo personalized medical products that are in increasing demand. SLM equipment Di-Metal100 self-developed by South China University of Technology is used. When the CoCrMo alloy satisThe process of selective laser melting (SLM) direct manufacturing based on CoCrMo alloy is studied to explore the optimized process of CoCrMo personalized medical products that are in increasing demand. SLM equipment Di-Metal100 self-developed by South China University of Technology is used. When the CoCrMo alloy satisfying the requirement of ASTM F75 is manufactured by SLM, three critical process parameters including laser power, scanning speed and scanning space are carried out process validation and analysis so that the process parameters with high relative density is obtained and through which the mechanical performance of parts manufactured is tested. The result shows that with the laser power of 170 W, scanning space of 0.08 mm and scanning speed of 500 mm/s, CoCrMo alloy samples manufactured directly by SLM with 99.02% relative density are obtained. Their tensile strength, yield strength σ0.2 and Rockwell hardness are all higher than the casting standard of ASTM F75 and their elongations are slightly lower. Through the process optimization of SLM direct manufacturing based on CoCrMo alloy, CoCrMo alloy personalized medical products meeting the target of medical product in performance can be manufactured, which provides important reference for personalized SLM direct manufacturing based on CoCrMo alloy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 603001 (2014)
Experimental Research on Laser Machining of Surface Micro-Textures of Carbide Cutting Tool
Su Yongsheng, Li Liang, He Ning, and Zhao Wei
Cutting tools with surface micro-textures have positive effects on reducing friction, improving the wear resistance and anti-adhesion. The comparative trials are carried out in fiber laser machining of micro-grooves and micro-holes on the rake face of cemented carbide cutting tool. The effects of various processing parCutting tools with surface micro-textures have positive effects on reducing friction, improving the wear resistance and anti-adhesion. The comparative trials are carried out in fiber laser machining of micro-grooves and micro-holes on the rake face of cemented carbide cutting tool. The effects of various processing parameters on topography and quality of micro-textures are analyzed, such as average output power, pulse repetition rate, defocusing distance. The experimental results show that the width of micro-grooves and the diameter of micro-holes have an increasing and a decreasing tendency with the increase of the average output power and the pulse repetition rate respectively. Furthermore, the morphologies of micro-textures can be improved by the larger average output power and the pulse repetition rate. It is observed that bottom morphologies of the micro-grooves is more uniform and smoother when the defocusing distance ranges from -1~-1.4 mm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 603002 (2014)
Dynamic Stress-Strain of Film-Substrate System Induced by Laser Shock Wave
Feng Aixin, Zhong Guoqi, Xue Wei, Shi Fen, Zhuang Xuhua, He Ye, and Chen Fengguo
The laser shocks of different pulse energies are used to perform a single impact on every multi-point of three kinds of the film-substrate system with different interface bonding strengths. The residual stress of target surface is detected by X-ray diffraction (XRD) technique, and the dynamic strain signal is collectedThe laser shocks of different pulse energies are used to perform a single impact on every multi-point of three kinds of the film-substrate system with different interface bonding strengths. The residual stress of target surface is detected by X-ray diffraction (XRD) technique, and the dynamic strain signal is collected by polyvinylidene fluoride (PVDF) sensor. Then a loading model of the laser shock wave on film-substrate system is established. Finally, the failure modes of film-substrate system based on laser discrete scratch are explored. The results show that the residual stress both on the surface of the 2024 aluminum alloy and the impact spot center of the film-substrate system increase after laser shock. The dynamic response of film-substrate system is related to the bond strength of film-substrate interface and the energy of laser. There are two failure modes of film-substrate system based on laser discrete scratch, one is the reflect stretch wave lead to membrane detached from the substrate, the other one is the shear stress of film-substrate system lead to film shear failure..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 603003 (2014)
Study on Fiber Laser Cutting of Aluminum Alloy Sheet
Chen Cong, Gao Ming, Gu Yunze, Wang Lei, Yang Huanqing, and Zeng Xiaoyan
To exploring fiber laser cutting of aluminum, fiber laser cutting of AA6061 Al alloy with the thickness of 2 mm is carried out. The effects of welding parameters such as laser power, cutting speed and the pressure of assisting gas on the quality of the kerf are investigated. The results show that accepted kerf can be oTo exploring fiber laser cutting of aluminum, fiber laser cutting of AA6061 Al alloy with the thickness of 2 mm is carried out. The effects of welding parameters such as laser power, cutting speed and the pressure of assisting gas on the quality of the kerf are investigated. The results show that accepted kerf can be obtained under appropriate parameters. The accepted kerf with the dross height less than 0.1 mm, the surface roughness less than 3 μm, and no megascopic gap as the kerfs are matched. It is found that when the laser power is 3.0 kW, the cutting speed of fiber laser that obtains accpeted kerf can be up to 9 m/min, which is two times than that of CO2 slab laser with the same laser power. Moreover, by increasing laser power to 3.0 kW, enhancing cutting speed rate to 6 m/min, raising stand-off to 0.5 mm, or increasing the pressure of assisting gas to 1.1 MPa, the dross height of the kerf is reduced to less than 0.1 mm. The minimum dross height is only 20 μm. The results show that the surface roughness is around 3 μm, and the minimum width of heat affected zone is 10 μm. Finally, a model is established by linear regression, whose estimated value agrees with experimental data well..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 603004 (2014)
Effect of Laser-Induced Plume on Welding Process During High Power Fiber Laser Welding
Zou Jianglin, Li Fei, Niu Jianqiang, Kong Xiaofang, Ma Ran, and Xiao Rongshi
The plate welding experiment is carried out by IPG YLS-600 fiber laser. The effect of plume is observed by a high speed camera, and measuring the weld width and penetration as the plume height is controlled by using the supersonic cross jet at different heights during bead-on-plate welding. The results show that the plThe plate welding experiment is carried out by IPG YLS-600 fiber laser. The effect of plume is observed by a high speed camera, and measuring the weld width and penetration as the plume height is controlled by using the supersonic cross jet at different heights during bead-on-plate welding. The results show that the plume can be divided into two parts: a randomly fluctuating plume out of the keyhole and a slender plume similar to the focused laser beam. The weld penetration and width have an improvement of about 20% and a decrease of about 24%, respectively, as the rising of plume is controlled by applying a cross jet at 5 mm height during welding. And the stability of the welding process and the appearances of the weld seam are also greatly improved. Further analysis indicates that the effect nature of plume on the fiber laser is the effect of particles in plume on the fiber laser, which results in a significant effect on the welding process..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 603005 (2014)
Microstructure and Mechanical Property of Laser Wire Fusion Brazing Welded Butt Joints of Steel/Aluminum Dissimilar Metal
Gao Wei, Yan Qi, and Huang Jian
Dissimilar metal butt joints of 2.5 mm thick 6013 aluminum alloy and galvanized low carbon steel are welded by fiber laser wire fusion brazing method. The microstructure of the fusion brazing welded joints is investigated by optical microscope, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS)Dissimilar metal butt joints of 2.5 mm thick 6013 aluminum alloy and galvanized low carbon steel are welded by fiber laser wire fusion brazing method. The microstructure of the fusion brazing welded joints is investigated by optical microscope, scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The joint strength is measured by tensile test. The effect of heat input on interface intermetallic compounds of aluminum/steel butt joint and joint strength are discussed. Experimental results show that butt joints with good appearance and certain tensile strength can be obtained under appropriate welding parameters. Further analysis reveal that this kinds of intermetallic compounds on the interface are mainly FeAl2 and FeAl3. With the increase of heat input, the thickness of the intermetallic compound is also increased. The uniform distribution of Al-Si eutectic along grain boundaries on α-Al substrate shows in welded seams. The maximum tensile strength of welded joints with a 30° groove is 88 MPa, the strength can reach up to 135 MPa when using a 45° groove..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 603006 (2014)
Performance of Aluminum Alloy Welded Joints by Laser Shock Processing
Xu Guojian, Zhong Liming, Wang Hong, Fu Xinhao, Wang Zhiyi, and Muneharu Kutsuna
In the present work, laser shock processing (LSP) using a Q-switch YAG laser facility with high pulsed peak power under water environment is implemented near the toes of A6061-T6 Aluminum alloy metal-inert gas (MIG) welded joints. And the properties of A6061-T6 aluminum alloy MIG welded joints is analyzed before and afIn the present work, laser shock processing (LSP) using a Q-switch YAG laser facility with high pulsed peak power under water environment is implemented near the toes of A6061-T6 Aluminum alloy metal-inert gas (MIG) welded joints. And the properties of A6061-T6 aluminum alloy MIG welded joints is analyzed before and after laser shock processing through the comparative method. The results show that after laser shock processing, Vickers hardness and fatigue life of the welded joints have been significantly improved, fatigue fracture of the welded joint without laser shock processing is located in or near the welded while it is located on the base material after laser shock processing, and a larger near-surface residual compressive stress with a maximum value of about -145 MPa is obtained. Compared with the base material, the surface roughness deteriorates after laser shock processing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 603007 (2014)
Effects of Welding Parameters on Bead Formation of Laser Welding under Subatmospheric Pressures
Luo Yan, Tang Xinhua, Lu Fenggui, Chen Qintao, and Cui Haichao
Deeper penetration depth and less pore sensitivity are the advantages of laser welding in vacuum. In order to make use of these advantages and eliminate the size limit of workpiece by the vacuum chamber as well, a new vacuum chamber is designed which can maintain a subatmospheric pressure above the welding molten pool.Deeper penetration depth and less pore sensitivity are the advantages of laser welding in vacuum. In order to make use of these advantages and eliminate the size limit of workpiece by the vacuum chamber as well, a new vacuum chamber is designed which can maintain a subatmospheric pressure above the welding molten pool. The chamber is fixed on the laser nozzle and the relatively lower pressure is generated with a vacuum pump. A series of spot welding and continuous welding experiments are taken under subatmospheric pressures. The results are compared with the weld bead under normal atmosphere with and without side-blowing shielding gas. The behaviors of plasma plume and molten pool are observed by the high-speed camera. The results show that the plasma plume is suppressed obviously and the penetration depth increases under subatmospheric pressure in spot laser welding. The penetration depth of spot weld bead is 4.5 mm deeper at most than the weld bead with side-blowing shielding gas. During continuous laser welding under subatmospheric pressure, the keyhole closed at the rear of the molten pool, the molten metal stacks backwards and sound weld can be achieved. The penetration depth of weld bead under subatmospheric pressure is averagely 2 mm deeper than the weld bead in normal atmosphere with side-blowing shielding gas..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 603008 (2014)
Laser Physics
Research of Automatic Frequency Stability Diode Laser
Zhang Yin, and Wang Qing
A novel frequency stabilization method is achieved. The variation of frequency is obtained by detecting saturated absorption signal, and the system is composed of a temperature coarse adjustment and a current fine adjustment to keep the frequency stabilization of the diode laser. The hardware and the software of the frA novel frequency stabilization method is achieved. The variation of frequency is obtained by detecting saturated absorption signal, and the system is composed of a temperature coarse adjustment and a current fine adjustment to keep the frequency stabilization of the diode laser. The hardware and the software of the frequency stabilization system based on micro control unit are outlined. Through the experimental test, it can automatically achieve frequency stabilization after power on, and can work continuously and stably in more than 180 days. The initial stability of the laser is 4.57×10-11 (1 s),3×10-12 (1024 s), 2.78×10-12 (8192 s) . It provides a method to realize the miniaturization and modularity of frequency stability diode laser..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 602001 (2014)
Error Control of Piston and Tilt Based on SPGD in Coherent Beam Combination
Mu Jie, Jing Feng, Wang Xiao, Zhu Qihua, Li Zhilin, and Zhang Junwei
Stochastic parallel gradient descent (SPGD) is an effective way to achieve multi-channel phase-locked laser beams for coherent beam combination (CBC). In this paper, the influence of piston error and tilt error on CBC is primarily presented. Then, an arrangement model of 2×2 laser beams is built. With this proposeStochastic parallel gradient descent (SPGD) is an effective way to achieve multi-channel phase-locked laser beams for coherent beam combination (CBC). In this paper, the influence of piston error and tilt error on CBC is primarily presented. Then, an arrangement model of 2×2 laser beams is built. With this proposed model, SPGD is tested and verified. Key parameters, the gain coefficient and the disturbance amplitude, impacts on the error control performance of the algorithm, are analyzed and optimized. The surveys show that it is necessary to control piston error and tilt error for CBC. When SPGD is used to correct the above errors, the convergence speed of the algorithm is improved with the increase of the gain coefficient and the disturbance amplitude, however, the accuracy of SPGD is reduced and the system is vibrated. In order to improve CBC, the adaptive gain coefficient is studied. Compared with the fixed gain coefficient, the adaptive gain coefficient is able to make a good balance between the convergence speed and the accuracy of the algorithm, which indicates that the adaptive gain coefficient is an effective optimization way. These results in this paper provide a theoretical reference for CBC using SPGD in a large short-pulse laser facility..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 602002 (2014)
Theoretical Investigation of High-Power Pulse-Pumped Er-Yb Codoped Fiber Amplifiers
Lü Xiaoying, Han Qun, and Liu Tiegen
Low-repetition rate high-power pulse-pumped Er-Yb codoped fiber amplifiers (EYDFAs) are theoretically investigated. By numerically solving the rate-equations of EYDFAs with finite difference method, in the case of limited amplified spontaneous emission (ASE), the impact of the peak-power and pulse-width of pump pulse aLow-repetition rate high-power pulse-pumped Er-Yb codoped fiber amplifiers (EYDFAs) are theoretically investigated. By numerically solving the rate-equations of EYDFAs with finite difference method, in the case of limited amplified spontaneous emission (ASE), the impact of the peak-power and pulse-width of pump pulse and time-delay between signal and pump pulse on the performance of the amplifier are systematically analyzed. The results show that the pulse width of pump pulse and the time delay between the signal and pump pulses have significant impact on the performance of EYDFA. They can be optimized by controlling the power of the ASE in a reasonable range. For a given gain medium, a low peak power long pump pulse is generally better than a high peak power short pulse, and there is an optimum value. These results are of great importame in high-power pulse-pumped Er-Yb codoped fiber amplifies..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 602003 (2014)
Small Signal Gain Measurement of Liquid Oxygen
Shi Zhe, Li Hui, Liu Jinbo, Zhou Canhua, Cai Xianglong, Cai Hongxing, Liu Wanfa, and Guo Jingwei
The small signal gain of the liquid oxygen around 1580 nm is measured using a tunable optical parametric oscillator (OPO) system. A small signal gain of 0.12 cm-1 is obtained at the wavelength of 1579.9 nm. The profile of small signal gain from 1579.2 nm to 1580.8 nm is also presented. The high positive gain indicates The small signal gain of the liquid oxygen around 1580 nm is measured using a tunable optical parametric oscillator (OPO) system. A small signal gain of 0.12 cm-1 is obtained at the wavelength of 1579.9 nm. The profile of small signal gain from 1579.2 nm to 1580.8 nm is also presented. The high positive gain indicates that the liquid oxygen is a potential medium for high energy laser. A comprehensive parameter optimization must be done in order to improve the small signal gain..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 602004 (2014)
Developmentof Compact 2 kHz mJ-Level 532 nm Laser as Laser Source of Lidar
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The green lidar is an effective tool for detecting aerosols. The laser in the lidar is a critical factor to the performance of lidar, because the progress of the laser can markedly improve the performance of lidar. Based on light source′s requirements of the micro pulse lidar, a compact high beam quality, high repetitiThe green lidar is an effective tool for detecting aerosols. The laser in the lidar is a critical factor to the performance of lidar, because the progress of the laser can markedly improve the performance of lidar. Based on light source′s requirements of the micro pulse lidar, a compact high beam quality, high repetition rate and high pulse energy diode end-pumped acousto-optically Q-switched 532 nm laser is developed, which can be used as the laser source in lidar. At the repetition rate of 2 kHz, the Q pulse with energy of 0.9 mJ and pulse width of 22 ns is generated. The beam factor M2 is less than 1.76 and the energy instability is ±2%. The laser is helpful to improve the detection distance, detection speed and detection precision of micro pulse lidar..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 602005 (2014)
Movement of the Core and the Centroid of Off-Center Gaussian Vortex Beams during Propagation
Ding Panfeng, and Pu Jixiong
While using the spiral phase plate (SPP) to produce Gaussian vortex beams, the center of the beam and the center of the SPP should be superposed. However, the center of the beam is always away from the center of the SPP to some extent in practice. The real output light from the phase plate are off-center Gaussian vorteWhile using the spiral phase plate (SPP) to produce Gaussian vortex beams, the center of the beam and the center of the SPP should be superposed. However, the center of the beam is always away from the center of the SPP to some extent in practice. The real output light from the phase plate are off-center Gaussian vortex beams. For conventional vortex beams, the core and the centroide are the same point and always located at the center during propagation. The off-center Gaussian vortex beam is different from the conventional vortex beams and its propagation is investigated in this paper. Research result shows that the core and the centroid of the off-center vortex beam are separate and moving during propagation. The directions of movement of the core and the centroid are decided by the sign of the topological charge. The movement distance of the core has no connection with the magnitude of the topological charge. However, the movement distance of the centroid is related to the magnitude of the topological charge..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 602006 (2014)
Thermal Analysis on Inertial Confinement Fusion Parallel Target Positioning System
Feng Bin, Liu Yanwu, Jia Huaiting, Wang Liquan, Yang Hui, and Lü Zhiwei
The parallel target positioning system is a new type of target positioning system used in the inertial confinement fusion (ICF) .The heat balance equation of the system is established based on analysis of principle of parallel target positioning system and heat transfer path. By analyzing the heat source in theory and The parallel target positioning system is a new type of target positioning system used in the inertial confinement fusion (ICF) .The heat balance equation of the system is established based on analysis of principle of parallel target positioning system and heat transfer path. By analyzing the heat source in theory and experiment, heat output power and temperature are determined. The temperature of the key parts of parallel target positioning mechanism is gotten by thermal analysis, which provides a theoretical basis for the design and accuracy analysis of the parallel target positioning system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 602007 (2014)
Influence of Structure Parameters for Two Sides Support on Third Harmonic Conversion Efficiency
Zhang Yang, Xiong Zhao, Xu Xu, Ye Lang, Yuan Xiaodong, Zhou Hai, and Zhang Bin
In final optics assembly of high-power solid-state laser, in order to improve the third harmonic generation (THG) efficiency, the method of both sides support for ultra-thin KDP crystals with large-aperture is adopted, and simulation model, is built using finite element analysis software. On this basis, the influence oIn final optics assembly of high-power solid-state laser, in order to improve the third harmonic generation (THG) efficiency, the method of both sides support for ultra-thin KDP crystals with large-aperture is adopted, and simulation model, is built using finite element analysis software. On this basis, the influence of parameters of clamping system including the number and length of support bars on the additional surface shape of KDP crystals, phase matching angle and THG efficiency are calculated and analyzed for the case of KDP crystals placed at different tilt angles. The results show that, when the number of support bars is four, the peak valley (PV) and root-mean-square (RMS) values of additional surface profile of ultra-thin KDP crystals with large-aperture, the mean value of crystal axis and THG efficiency almost keep unchanged with the length of support bars and an ideal THG efficiency is achieved. Consequently, the problems of repeating test on the quality of KDP crystals′ surface profile can be solved, and the time for engineering assembly and calibration can be reduced..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 602008 (2014)
Materials and Thin Films
Yb3+/Al3+ Co-Doped Silica Glass Prepared by Melting Technology Based on High-Frequency Plasma
Wang Chao, Zhou Guiyao, Han Ying, Xia Changming, and Zhao Yuanyuan
In order to solve the problem, such as high melting point of Yb3+/Al3+ co-doped silica glass and being difficult to be prepared, the Yb3+/Al3+ co-doped silica glass is prepared by the powder melting technology based on the high-frequency plasma and the related theory and technology are researched. The technology providIn order to solve the problem, such as high melting point of Yb3+/Al3+ co-doped silica glass and being difficult to be prepared, the Yb3+/Al3+ co-doped silica glass is prepared by the powder melting technology based on the high-frequency plasma and the related theory and technology are researched. The technology provides the possibility to fabricate very large and multicore rare earth doped photonic crystal fiber (PCF), and single or multiple kinds of rare earth ion doping can be realized. The bubble in the glass is eliminated and the reduction of Yb3+ ion is inhibited by adding auxiliary heating device and using oxygen as the melting atmosphere, respectively. The Yb3+/Al3+ co-doped PCF is drawn by the stack and draw technology using the glass as the PCF core. The background attenuation value of the PCF at 1200 nm is less than 0.25 dB/m, and the laser is emitted in the laser system by using the PCF as the gain medium. The test results indicate that the Yb3+/Al3+ co-doped silica glass prepared by the technology has good optical properties..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 606001 (2014)
Design and Properties Analogy of ZnO-Based Multilayer Transparent Conducting Film
He Xiaoxiao, Wang Wenjun, Li Shuhong, Liu Yunlong, and Shi Qiang
Transparent conducting films are widely used in flat panel display, photo voltaic solar cell and other lighting industries. The decreasing thickness of transparent conducting film expands the application of those films. The different thicknesses of single ZnO film and ZnO/Au/ZnO structure films are deposited by laser mTransparent conducting films are widely used in flat panel display, photo voltaic solar cell and other lighting industries. The decreasing thickness of transparent conducting film expands the application of those films. The different thicknesses of single ZnO film and ZnO/Au/ZnO structure films are deposited by laser molecular beam epitaxy system at a pressure 1.0×10-5 Pa. A high quality transparent electrode with resistivity as low as 6.89×10-4 Ω·cm and high transmittance of 80% in visible region is obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 607001 (2014)
Measurement and Metrology
System Contributing to Install Inside Sleeve and Filtering Algorithm to Evaluate Its Roundness Error
Liu Jie, Li Hua, Chang Hemin, and Jiang Xin
Nuclear evaporator has two sleeves, outside sleeve and inside sleeve. To install inside sleeve accurately, the concentricity of the two sleeves and the roundness error of inside sleeve should be evaluated. The system which contributes to install inside sleeve of nuclear evaporator is developed. It is introduced that thNuclear evaporator has two sleeves, outside sleeve and inside sleeve. To install inside sleeve accurately, the concentricity of the two sleeves and the roundness error of inside sleeve should be evaluated. The system which contributes to install inside sleeve of nuclear evaporator is developed. It is introduced that the parts of the system and the measuring process. The position forms among three close points are divided into three forms: convex, concave and collinear in the data processing. And it is found out how to filter the points that can′t fix maximum inscribed circle. Based on that, the filtering algorithm is presented. This algorithm is efficient and easy to be understood. It can save the data processing time. In practical application, the measuring accuracy of the whole system is 0.7 mm, which can meet the needs of project and have practical value..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 608002 (2014)
Measurement and Metrology
300 mm-Travel Stage of Grating Ruling Engine and Its Self-Adaptive Control Method
Li Xiaotian, Yu Haili, Qi Xiangdong, Zhu Jiwei, Yu Hongzhu, and Bayanheshig
Stage properties and its control algorithms of grating-ruling engine are important reasons that directly influence the ruling accuracy of large grating. In order to improve the running accuracy of grating ruling engine, a 300 mm travel macro-micro stage using PZT as actuator of the micro positioning stage is developed.Stage properties and its control algorithms of grating-ruling engine are important reasons that directly influence the ruling accuracy of large grating. In order to improve the running accuracy of grating ruling engine, a 300 mm travel macro-micro stage using PZT as actuator of the micro positioning stage is developed. Mathematical model of micro-positioning stage is established, and the influence of stage′s parameters on the dynamic performance of the system is analyzed by simulation. Micro-positioning stage is closed-loop controlled by BP neural network proportion integration differentiation (PID) method. Simulation results show that the dynamic performance of micro-positioning stage which is closely related with grating quality can be improved in general trend by increasing the stiffness or damping between inside and outside stage. Positioning experiments of stage, which is used to emptily rule 35 line/mm or higher line density grating and employ dual-frequency laser interferometer as nano-positioning measurement standard, show that BP neural network PID algorithm can achieve 3σ positioning error of macro-micro stage to be no more than 5.0 nm. The studies above can provide theoretical and technical guidance for structure design and control-algorithm choice of macro-micro stage of large grating ruling engine..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 608001 (2014)
Micro and Nano Optics
Influence of Coupling Gap on the Performance of Silicon-no-Insulator Microring Resonator
Li Minghui, Ma Kezhen, Luo Liang, Guo Zebin, Zhang Anfu, Xue Chenyang, Zhang Wendong, and Yan Shubin
Microring resonators with different coupling gaps are fabricated by micro-electro-mechanical-systems (MEMS) technology. To acquire the relationships of coupling gap with coupling coefficient and resonance depth, the theoretical analysis, simulation and coupling experiment are carried out. The test results show that, wiMicroring resonators with different coupling gaps are fabricated by micro-electro-mechanical-systems (MEMS) technology. To acquire the relationships of coupling gap with coupling coefficient and resonance depth, the theoretical analysis, simulation and coupling experiment are carried out. The test results show that, with the increase of the coupling gap, coupling coefficient decreases and coupling depth becomes shallower, which are consistent with simulation. Actual calculation of the coupling efficiency, 3 dB bandwidth and quality factor show that,as the gap increasing, the coupling efficiency becomes lower, 3 dB bandwidth turns narrower and the quality factor increases. The results provide a foundation for further design and optimization of microring resonator and its research and application in related fields..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 610001 (2014)
Optical Communication
Upstream Date Transmission Based on Wavelet Packet Transform Coding in Passive Optical Network
Wang Yimeng, Li Wei, Han Jilong, Yao Haitao, Yu Shaohua, and Yang Qi
An upstream date transmission method from optical network units (ONUs) to the optical line terminal (OLT) based on wavelet packet multi-level orthogonal coding in passive optical networks (PON) is proposed and studied. Each ONU can be assigned a special coding based on the wavelet packet coding method to share a waveleAn upstream date transmission method from optical network units (ONUs) to the optical line terminal (OLT) based on wavelet packet multi-level orthogonal coding in passive optical networks (PON) is proposed and studied. Each ONU can be assigned a special coding based on the wavelet packet coding method to share a wavelength. As the wavelet packet coding method is used, the number of ONU can be very large. And there are no need for the burst mode transmitter/receiver module and multi-wavelength lasers. So the proposed system has the advantages of low cost, high data transmission rate and large access number. This upstream system architecture model is established and simulated at the transmission rate of 1.25 Gb/s and 10 Gb/s. Simulation results show 32 ONUs, where each ONU is with a data rate of 10 Gb/s, and the total transmission rate is up to 320 Gb/s..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 605001 (2014)
Ultraviolet Multipath Scattering Link Model under the Influence of High Altitude Turbulence
Qiang Ruoxin, Zhao Shanghong, Wang Xiang, and Liu Yun
Considering the air pressure, temperature, ozone concentration and turbulence vertical distribution of scattering communication link in the upper-air, a ultraviolet multipath scattering ling model is modified, combined with Rayleigh scattering theory. The scattering volume is divorced into scattering elements and each Considering the air pressure, temperature, ozone concentration and turbulence vertical distribution of scattering communication link in the upper-air, a ultraviolet multipath scattering ling model is modified, combined with Rayleigh scattering theory. The scattering volume is divorced into scattering elements and each element corresponds to every path. Signal strengths of each beams of laser divorced according to different paths are computed respectively. The probability density districutions of each non-line-of-sight signal strengths are calculated by logarithm-normal distribution and non-line-of-sight link turbulence model. Finally, total signal strength probability densities of each path signal in receiving terminal and the link losses are got by the way of each probability density convolutions. According to the factual atmosphere environment, the results show that the newly built probability density distribution is more concentrated. The differential distinction between extinction coefficient and absorption coefficient vertical distribution functions lies 15 km, due to the great impact of ozone absorption. At the range from 2 km to 14 km in the upper-air, scintillation index is higher with transmitter and receiver at the height of 11 km, while it is the lowest with transmitter and receiver at the height of 6 km. Considering turbulence and path loss, transmitter and receiver can be set below 10 km in the upper-air when ultraviolet communication is used in high atmosphere..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 605002 (2014)
Refractive Index Sensing Property of SiO2-Al2O3-SiO2 Photonic Crystal Defect Cavity
Chen Ying, Lu Bo, and Fan Huiqing
To improve the sensitivity and the Q value of the photonic crystal refractive index sensor, a coupling structure combining the defect photonic crystal and the prism based on surface wave resonance theory is proposed. The sensing theoretical model is established by the layered transfer matrix method and the relationshipTo improve the sensitivity and the Q value of the photonic crystal refractive index sensor, a coupling structure combining the defect photonic crystal and the prism based on surface wave resonance theory is proposed. The sensing theoretical model is established by the layered transfer matrix method and the relationship between the Goos-Hnchen shift and the resonant wavelength is obtained, which can deduce the relationship model between the resonant wavelength and the refractive index of the sample detected. The SiO2-Al2O3-SiO2 structure is regarded as the defect cavity, which is replaced by the gold film in conventional surface plasmon resonance (SPR) sensor. Al2O3 is adopted as the absorbed layer, and then the resonant defect peak wavelength can be obtained and the dynamic detection of the refractive index of sample can be achieved from the shift of the resonant defect peak wavelength. The ethylene glycol is adopted as the sample detected and the Q value and the sensitivity of the refractive index sensing structure are discussed. The simulation results show that the sensitivity can attain to 3596 nm·RIU-1 (RIU is refractive index unit) and the Q value is 1087.7 approximately, which demonstrates the effectiveness of the sensing structure. The design scheme can provide certain theoretical guidance for high sensitivity and high Q value sensor design..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 605003 (2014)
An AMA-DWT-DMKF Method for Fiber Optic Gyroscope Signal Filtering
Gao Weiwei, Wang Guanglong, Zhang Chunxi, Chen Jianhui, and Gao Fengqi
In order to solve the contradiction between noise suppression and signal tracking in filtering for fiber optic gyroscope (FOG), a method as AMA-DWT-DMKF is proposed. Using the AMA algorithm, FOG output signal is divided into a signal transition region and a stability region, and combining the advantages of two algorithIn order to solve the contradiction between noise suppression and signal tracking in filtering for fiber optic gyroscope (FOG), a method as AMA-DWT-DMKF is proposed. Using the AMA algorithm, FOG output signal is divided into a signal transition region and a stability region, and combining the advantages of two algorithms such as DWT and Kalman with different Q/R values, in the end giving a targeted filtering for the results of the AMA algorithm. The proposed method is used for denoising the static signal, disturbance signal and the change rate signal. Experimental results show that the proposed algorithm not only has higher denoising capability, but also has a better signal tracking capability..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 605004 (2014)
Study of Coherent Optical Wavelength Division Multiplexing Terabit Transmission Experiment System Based on Multi-Carrier
Zhang Xia, Tian Feng, Zhang Xiaoguang, and Bai Chenglin
20-tone, 25 GHz spacing multi-carrier with the tone-to-noise ratio (TNR) larger than 25 dB is generated based on recirculating frequency shifter (RFS). Each subcarrier is modulated with a return-zero 16-quadrature amplitude modulation (RZ-16QAM) signal at 16 Gbaud and then polarization division multiplexing (PDM) is em20-tone, 25 GHz spacing multi-carrier with the tone-to-noise ratio (TNR) larger than 25 dB is generated based on recirculating frequency shifter (RFS). Each subcarrier is modulated with a return-zero 16-quadrature amplitude modulation (RZ-16QAM) signal at 16 Gbaud and then polarization division multiplexing (PDM) is employed to further increase the capacity. At last, 2.56 Tbit/s, PDM-RZ-16QAM, coherent optical wavelength division multiplexing (CO-WDM) transmission over 792 km standard single-mode fiber (SSMF) with 25 GHz channel spacing using coherent detection is experimentally demonstrated. Compared to the theoretical limits, the measured optical signal to noise ratio (OSNR) sensitivity curve in back-to-back system is shifted by approximately 4.1 dB at a bit-error rate (BER) of 1×10-3. After transmission, the BER value of 4.5×10-3 at the optimal launchpower is under the threshold value of soft-decision forward error correction (FEC) of 2.4×10-2, and the corresponding constellations diagrams of x and y polarizations for recovered CO-WDM PDM-RZ-16QAM signals of the central channel show the excellent performance. The spectrum efficiency of our transmission system is 5.1 bit/(s·Hz)..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 605005 (2014)
Multi-Wavelength Fiber Laser Employing Twin-Core Fiber Filter and Nonlinear Polarization Rotation
Feng Suchun, Ren Wenhua, Chen Manya, and Peng Wanjing
Multi-wavelength erbium-doped fiber laser based on twin-core fiber filter and nonlinear polarization rotation at room temperature is proposed. The compact in-fiber Mach-Zehnder comb-filter is formed by splicing a section of twin-core fiber (TCF) with two single mode fibers (SMFs). Due to the nonlinear polarization rotaMulti-wavelength erbium-doped fiber laser based on twin-core fiber filter and nonlinear polarization rotation at room temperature is proposed. The compact in-fiber Mach-Zehnder comb-filter is formed by splicing a section of twin-core fiber (TCF) with two single mode fibers (SMFs). Due to the nonlinear polarization rotation (NPR) effect in the laser cavity, the laser can be made to operate in stable multi-wavelength lasing states by adjusting the states of the polarization controller (PC) appropriately. The wavelength shift is less than 0.02 nm, and the power amplitude variation is less than 0.4 dB, which shows the fiber laser has a good stability..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 605006 (2014)
Performance Enhancement of LDPC in 100 Gb/s PDM-DQPSK Optical Communication Using a Water-Bit Based on Channel Estimation
Li Chao, Zhang Wenbo, Zhang Xiaoguang, Xi Lixia, Tang Xianfeng, and He Wenxue
To reduce the interference caused by channel noise and polarization mode dispersion (PMD) in the optical communication, a modified forward error correction method is studied. By inserting fixed bits which are defined as the watermark bits (water-bit ) into the low density parity check (LDPC) codes to estimate the channTo reduce the interference caused by channel noise and polarization mode dispersion (PMD) in the optical communication, a modified forward error correction method is studied. By inserting fixed bits which are defined as the watermark bits (water-bit ) into the low density parity check (LDPC) codes to estimate the channel, a new decoding algorithm which is combined with channel estimation is proposed. The results show that the LDPC code with 16、 32 water-bit transmitted over Gaussian channel outperforms the conventional LDPC code transmitted over Chi-square channel in the error correction performance, and with bit error rate (BER) below 10-9 as standard, the optical signal to noise ratio (OSNR) value can reduce about 0.25 dB、 0.35 dB. When PMD is considered in the high-speed optical communications, the LDPC code with 16、 32 water-bit has a better tolerance than the conventional LDPC code, when differential group delay (DGD) is 20 ps and 30 ps, the OSNR value can reduce about 0.63 dB、 0.98 dB and 1.16 dB、 1.87 dB..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 605007 (2014)
Correction of Pointing Angle Deviation and In-Orbit Validation in Satellite-Ground Laser Communication Links
Wu Feng, Yu Siyuan, Ma Zhongtian, Ma Jing, and Tan Liying
For the first satellite-ground laser communication links of China, beam pointing deviations are existed due to the coordinate system pointing errors of terminal adjustment and installation. The pointing angle deviation is 8 mrad and the acquisition time is larger than 40 s, which have a serious effect on the acquisitioFor the first satellite-ground laser communication links of China, beam pointing deviations are existed due to the coordinate system pointing errors of terminal adjustment and installation. The pointing angle deviation is 8 mrad and the acquisition time is larger than 40 s, which have a serious effect on the acquisition performance. Based on that, the transformation matrix between the satellite coordinate system and the terminal coordinate system is given based on the cubic mirror correction system. At last the correction angles are obtained and the correction of pointing brought by ground station is made. The in-orbit test results of haiyang-2 (HY-2) show that the pointing angle deviation between terminal and ground situation decreases from 8 mrad to 0.8 mrad, the scan area is decreased and the acquisition time of optical communication terminal decreases from 40 s to less than 5 s. The in-orbit experimental results show that this method can be accurate to compensate on the pointing deviations than that of other countries, revising the results to meet the requirements of the laser communications link established..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 605008 (2014)
Relative Intensity Noise Characteristic of Broadband Sources and its Effect on Performance of Closed-Loop Fiber Optic Gyroscope
Suo Xinxin, Yang Yuanhong, Yang Mingwei, Ma Haiquan, and Zhang Bin
The accurate evaluation of relative intensity noise (RIN) of broad-band sources and its effect mechanism on a fiber optic gyroscope (FOG) are key factors to further improve the performance of FOGs. An intensity noise measurement system is constructed and RINs of four sources with different spectral shapes and degree ofThe accurate evaluation of relative intensity noise (RIN) of broad-band sources and its effect mechanism on a fiber optic gyroscope (FOG) are key factors to further improve the performance of FOGs. An intensity noise measurement system is constructed and RINs of four sources with different spectral shapes and degree of polarizations are tested. Then the RINs are calculated with three different effective bandwidths and the accurate RIN model is confirmed by employing the power weighted average (PWA) bandwidth. Based on this research, the random walk coefficient (RWC) model of FOG is modified. A photoelectric detachment high precision FOG is constructed, and the RWC of FOG is tested with four broadband sources and calculated by using the modified model. It is shown that the calculation results are consistent with the experiment results. This indicates that the power weighted average bandwidth and the degree of polarization are key factors determining the RIN of broadband sources and this research is of great value in evaluating the RIN characteristics of different sources and designing high performance FOGs..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 605009 (2014)
Rapid Communications
[in Chinese]
[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. 41, Issue 6, 602001 (2014)
Optical Design and Fabrication
Manufacture and Application of Large Aperture Standard Transmission Spheres
Xue Donglin
In order to realize testing of a large aperture convex sphere, large aperture standard transmission spheres are designed and manufactured. The system focal length of 4400 mm, Φ 350 mm aperture are required. The design and performance comparison, surface quality and radius of curvature testing, large aperture SiC convexIn order to realize testing of a large aperture convex sphere, large aperture standard transmission spheres are designed and manufactured. The system focal length of 4400 mm, Φ 350 mm aperture are required. The design and performance comparison, surface quality and radius of curvature testing, large aperture SiC convex sphere surface testing are complished. The simulation result analysis of optical design software shows that the wavefront performance of the system design is 0.0001λ [peak to valley (PV), λ=632.8 nm], and it can offer a high-quality spherical wave and the reference spherical surface quality is up to 0.088λ (PV, λ=632.8 nm), 0.006λ [root mean square (RMS), λ=632.8 nm]. For a SiC convex sphere of Φ320 mm aperture and 4092 mm radius of curvature the manufactured results of the surface quality are up to 0.102λ (PV, λ=632.8 nm), 0.011λ (RMS, λ=632.8 nm). The results indicates that the large aperture standard transmission spheres are helpful for the testing large aperture convex sphere surface with large radius of curvature, the highly precision testing is complished only by standard sphere and non-null testing method based on digital mask, and the problems of large-aperture convex asphere or freeform mirror testing are solved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 616001 (2014)
Design of Wollaston Prism Used for Polarization Illumination System in ArF Lithography Tool
Cai Yanmin, Wang Xiangzhao, and Huang Huijie
Wollaston prism is used as a polarizer in ArF lithography tool polarization illumination system. Wollaston prism is made of one kind of material used at 193 nm wavelength, the beam separation angle is very small and the prism is very long. In order to solve these practical problems, Wollaston prisms made of positive crWollaston prism is used as a polarizer in ArF lithography tool polarization illumination system. Wollaston prism is made of one kind of material used at 193 nm wavelength, the beam separation angle is very small and the prism is very long. In order to solve these practical problems, Wollaston prisms made of positive crystal are analyzed by the law of refraction, and the beam separation angle formulas are derived. A result is presented that the beam separation angle of Wollaston prism made of two kinds of positive crystal is more than that of Wollaston prism made of single positive crystal after analysis and comparison by MATLAB. A Wollaston prism with the beam separation angle of about 10° is designed at wavelength of 193 nm. Another Wollaston prism only with a output beam of linearly polarized light is designed at wavelength of 193 nm. The two prisms are made of positive crystal, the lengths of both the two prisms are medium, which can be used for the polarization illumination system in ArF lithography tool..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 616002 (2014)
Remote Sensing and Sensors
Remote Sensing Image Coding Based on Direction Optimal Lifting Strategy
Zhang Libao, Qiu Bingchang, Yang Xuye, and Zhao Huigang
The traditional lifting wavelet transform cannot be effectively reconstructed non-horizontal and non-vertical high-frequency information of remote sensing images, which results in these high frequency wavelet coefficients to be still salient relatively and reduces the coding efficiency of remote sensing images. A new lThe traditional lifting wavelet transform cannot be effectively reconstructed non-horizontal and non-vertical high-frequency information of remote sensing images, which results in these high frequency wavelet coefficients to be still salient relatively and reduces the coding efficiency of remote sensing images. A new lifting wavelet scheme based on direction optimal model called direction optimal lifting wavelet (DOLW) is proposed. The new algorithm first designs a directional prediction model based on gradient to obtain optimal transform direction of lifting wavelet. It executes the directional lifting transform in the direction of the first vertical along the optimal transform direction. The edge and texture energy can be weaken on the non-horizontal and non-vertical direction of the high-frequency subband of the remote sensing image. The new algorithm uses sampling function interpolation to predict the value of sub-pixels. The experimental results for these remote sensing images show that, compared with traditional lifting wavelet transform, the new algorithm improves the peak signal-to-noise ratio (PSNR) and the subjective quality of the reconstructed images significantly. So the new algorithm has important value for the remote sensing image compression and coding in the future..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 614001 (2014)
Sensitivity Property Analysis of Biosensors Based on Particle Swarm Optimization
Chen Ying, Wang Wenyue, and Bi Weihong
To improve the normalized transmission of photonic crystal biosensors based on the air-pore structure, the particle swarm optimization algorithm has been adopted to optimize the structure parameters globally in the multi-dimensional space. The optimization process has been performed according to the position-velocity uTo improve the normalized transmission of photonic crystal biosensors based on the air-pore structure, the particle swarm optimization algorithm has been adopted to optimize the structure parameters globally in the multi-dimensional space. The optimization process has been performed according to the position-velocity updating equation, in which the coupling structure combining the ring cavity with the line waveguide is regarded as the optimized object, and the scattering air pores, the coupling air pores and the inner air pores are regarded as the optimized variables. Then the sensing property has been analyzed using the optimized structure, in which the coupling area and the inner area have been adopted as the sensing region respectively. The simulation results show that the normalized transmission can be increased from 54% to 92% after optimization and the relationship between shift of the resonant wavelength and the change of the refractive index for the biological sample is linear. And the sensitivity of the inner air pores as the sensing region is higher than those of the general chip and the coupling air pores with the sensitivity more than 950 nm/RIU. The structure optimization method can provide effective guidance for other functional devices and integrated optical waveguide devices..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 614002 (2014)
Fiber Laser Ranging System Based on Different Pseudorandom Code Modulation
[in Chinese]
Different pseudorandom codes are adapted in laser ranging system based on high modulation rate and photon counting technology. Ranging performance is compared and demonstrated between different pseudorandom codes and M sequence using fiber delay method of ranging experiments. Under the same incident condition, better sDifferent pseudorandom codes are adapted in laser ranging system based on high modulation rate and photon counting technology. Ranging performance is compared and demonstrated between different pseudorandom codes and M sequence using fiber delay method of ranging experiments. Under the same incident condition, better signal of noise ratio and ranging accuracy are acquired when using M sequence. The actual ranging platform is established and ranging experiment outdoor is carried out. Ranging accuracy of 3.2 cm is obtained when the laser transmit to a target which distance is about 768.5 m under the condition of the transmitter peak power of 12.1 W, 10 order M pseudorandom sequence and 1 GHz modulation rate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 614003 (2014)
Spectroscopy
Research on the Measurement Method of MgO Content in Cement by Laser Induced Breakdown Spectroscopy
Li Wenhong, Wu Zhixiang, Wang Ruiwen, and Shang Liping
MgO is one of the main substances which are required to be accurately determinated in cement. The plasma spectra of ordinary silicate cement obtained by laser-induced breakdown spectroscopy (LIBS) are analyzed. Mg I 517.2 nm characteristic line is selected as the analysis line. By measuring the spectral intensities of MgO is one of the main substances which are required to be accurately determinated in cement. The plasma spectra of ordinary silicate cement obtained by laser-induced breakdown spectroscopy (LIBS) are analyzed. Mg I 517.2 nm characteristic line is selected as the analysis line. By measuring the spectral intensities of the signals and the corresponding signal-to-noise ratios with different laser energies. It′s found that the optimal energy is 40 mJ. In order to reduce the error, the ratio of the spectral line intensity of Mg 517.2 nm and the spectral integral from 516 nm to 520 nm is used as internal standard to establish the MgO mass fraction calibration curve. The carrelation coefficient of calibration curve is 0.9959. Cycle inversion method is used to detect the accuracy of MgO quantitative analysis. The maximum relative error and the mean relative error are 5.9% and 2.48%. The detection limit of MgO mass fraction in cement obtained by LIBS is 0.51%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 41, Issue 6, 615001 (2014)
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