Journals >Chinese Journal of Lasers
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2015
Volume: 42 Issue 2
50 Article(s)
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Directional Couplers Based on MIM Plasmonic Waveguide Stuctures
Wang Jicheng, Jiang Yalan, Wang Yueke, Liu Cheng, Tang Baojie, and Sun Lin
The metal-insulator-metal (MIM) based bending waveguide structures with a quadrant ring resonator (QRR) are presented in theory. Those structures can control the directional propagation of plasmonic waves in waveguide cross junctions. The transmission of various wavelengths in straight waveguide with a quadrant ring reThe metal-insulator-metal (MIM) based bending waveguide structures with a quadrant ring resonator (QRR) are presented in theory. Those structures can control the directional propagation of plasmonic waves in waveguide cross junctions. The transmission of various wavelengths in straight waveguide with a quadrant ring resonator based on finite-different time-domain (FDTD) method is studied, and optical properties of the barrier thickness between quadrant ring resonator and communication waveguides are also studied. The simulation results demonstrate that the waveguide structure can achieve higher transmission, and achieve the filtering effects at the specific wavelength positions. In addition, three and four waveguide branches structures are proposed. The structures can obtain the effects of directional transmission of surface plasma wave in the waveguide bends, such as beam splitting, total reflection. The structures have the effects of strong beam binding, nanometer-scale transmission, and can solve the problem of signal transmission and reflection. Those design structures have an important application prospects in optical integration, communication, information processing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 217001 (2015)
Optical Limiter for Ultrashort Laser Pulses Baesd on Ultrafast Optical Kerr Effect
Song Honglei, Yan Lihe, Si Jinhai, and Hou Xun
Ultrashort pulse laser has important potential applications in the field of optoelectronic countermeasure because of its unique propagation features. An ultrafast optical limiter based on optical Kerr effect for ultrashort laser pulses is proposed on account of the problems in the traditional optical limiting (OL) methUltrashort pulse laser has important potential applications in the field of optoelectronic countermeasure because of its unique propagation features. An ultrafast optical limiter based on optical Kerr effect for ultrashort laser pulses is proposed on account of the problems in the traditional optical limiting (OL) method. The proposed OL technique utilizes the nonlinear polarization ellipse rotation (NER) effect induced in nonlinear materials to realize an excellent OL performance with ultra- low activating threshold. By combining NER and self- focusing effects, the proposed optical limiter can be used in a large dynamic range. The proposed optical limiter also has advantages of ultrafast response time and wide applicable spectral range. The basic principles of NER effects is discussed systematiclly, and OL performance of the limiter is verified using a femtosecond pulse laser..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 217002 (2015)
Research Article
Simulation of Water Vapor Multiple Wavelengths Lidar Echo Signals and Error Analysis
Li Ting, Chen Siying, Zhang Yinchao, Guo Pan, Chen He, and Gao Long
The concentration of atmospheric water vapor decreases sharply as the attitude increases. In order to obtain an accurate distribution of water vapor in atmosphere, a spaceborne range- resolved differential absorption lidar (DIAL) of multiple wavelengths emission is designed. Four wavelengths are identified with small dThe concentration of atmospheric water vapor decreases sharply as the attitude increases. In order to obtain an accurate distribution of water vapor in atmosphere, a spaceborne range- resolved differential absorption lidar (DIAL) of multiple wavelengths emission is designed. Four wavelengths are identified with small diffeerences in wavenumbers, and with different water vapor absorption cross sections, where three wavelengths with larger cross sections are considered to be signal beams, and the last one with smaller cross section is called the reference beam. Divided into three groups, the concentrations of water vapor at different elevations can be segmentally detected. The echo signals of the four wavelengths are simulated. To verify the performance of water vapor profiles detection, the random systematic relative errors of three groups detections of DIAL from spaceborne platforms in daytime and nighttime are evaluated. The analysis shows that, under relative error less than 20% , water vapor profile measurement is possible under troposphere (less than altitude of 12 km) in daytime, and under the bottom of the stratosphere (less than altitude of 15 km) at night. It is theoretically and preliminary proved that the multiple wavelengths spaceborne range-resolved DIAL has the ability of accurate detection of water vapor concentration distributions in troposphere..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 213001 (2015)
Sun Centroid Extraction Algorithm for Solar Tracker with Double Modes
Jiang Chunxia, Wang Canjin, and Chen Juan
On the basis of traditional solar tracker, a new solar tracker with double modes is built using image processing technology. The theme is focus on sun centroid extraction algorithm for solar tracker. To handle the problem that the solar tracker cannot track accurately when the sun is obscured by clouds or fogs, an imagOn the basis of traditional solar tracker, a new solar tracker with double modes is built using image processing technology. The theme is focus on sun centroid extraction algorithm for solar tracker. To handle the problem that the solar tracker cannot track accurately when the sun is obscured by clouds or fogs, an image dehazing method based on rapid median filter is proposed. The transmission map is estimated by dark channel prior, and is smoothed using fast median filtering instead of soft- matting. The dehazed image is estimated using the transmission map. In order to avoid segmentation errors caused by manual threshold, an improved fast manimally stable extremal region (MSER) feature regions extraction method is proposed to extract sun area, and the centroid of the sun is computed. The experimental results indicate that the proposed algorithm can restore images captured in foggy and hazy weather, and accurately extract the centroid of the sun. The proposed method has low computational complexity and it meets the real-time processing acquirement of solar tracker..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 213002 (2015)
Biomedical Photonics and Laser Medicine
Imaging by Optically Scattering Objects and Absorption Objects with Ultrasound-Modulated Optical Tomography
Zhu Lili, and Li Hui
Ultrasound-modulated optical tomography (UOT) has high spatial resolution of ultrasonic location and high sensitivity of optical detection. Both of scattering objects and absorption objects can be imaged by UOT. The signal to noise ratio and image contrast of UOT is improved by laying two apertures between the sample aUltrasound-modulated optical tomography (UOT) has high spatial resolution of ultrasonic location and high sensitivity of optical detection. Both of scattering objects and absorption objects can be imaged by UOT. The signal to noise ratio and image contrast of UOT is improved by laying two apertures between the sample and the detector (photomultiplier tube, PMT) and choosing appropriate position of PMT. One dimensional imaging of scattering objects and absorption objects buried in turbid media is provided. The experimental results indicate that the relationship between modulation depth of ultrasound-modulated signal and the scattering and absorption properties of media is dependent on detection position of PMT. The scattering objects and absorption objects are imaged simultaneously and distinguishable when PMT is at an appropriate position..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 204001 (2015)
Holography and Information Processing
Adaptive Enhancement Algorithm for Low Illumination Images Based on Wavelet Transform
Li Qingzhong, and Liu Qing
A fast and adaptive enhancement algorithm for low illumination images based on wavelet transform is presented. RGB color image is converted to HSV color space, and the luminance component V is decomposed to low frequency sub-band and high frequency sub-bands by discrete wavelet transform (DWT). The illumination componeA fast and adaptive enhancement algorithm for low illumination images based on wavelet transform is presented. RGB color image is converted to HSV color space, and the luminance component V is decomposed to low frequency sub-band and high frequency sub-bands by discrete wavelet transform (DWT). The illumination component is estimated and removed using bilateral filtering from the low frequency subband quickly, and the high frequency sub- bands corresponding to the image edges and texture are enhanced and de- noised using transform of fuzzy set. Based on the proposed histogram objective function, the contrast of the resulted V image is enhanced adaptively and quickly by employing the optimization method combining the Powell with the simulated annealing algorithm. The visibility improved color image is generated by combining the enhanced V image with H and S chrominance components. The experimental results show that the proposed algorithm can improve the visibility of low illumination images quickly and effectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 209001 (2015)
Laser Manufacturing
Study of Ti∶Sapphire Double Line Waveguide Written by Femtosecond Laser
Liu Shuang, Liu Xin, Tang Wenlong, and Cheng Guanghua
Ti∶sapphire crystal is one of the most important materials as a laser medium, due to its broad absorption band and widely tunable output band, therefore it has wide application in integrated optics. By femtosecond laser with repetition rate of 1 kHz, central wavelength of 800 nm and pulse width of 120 fs, double line wTi∶sapphire crystal is one of the most important materials as a laser medium, due to its broad absorption band and widely tunable output band, therefore it has wide application in integrated optics. By femtosecond laser with repetition rate of 1 kHz, central wavelength of 800 nm and pulse width of 120 fs, double line waveguide in Ti∶sapphire crystal is transversely written. The impacts of the processing conditions, i.e., inscribing depth, writing speed and the track distance on the waveguide formation are systematically studied, and the waveguide with better guiding mode is achieved when laser pulse energy is 2 μJ, inscribing depth is 175 μm , writing speed is 90 μm/s and the distance between two tacks is 26 μm. And the double line waveguide shows polarization dependent optical guiding. Based on the near-field mode intensity, the refractive index profile of the optical waveguide is reconstructed, and the max positive refractive index change is about 1.9 × 10-4 . In addition, by using the scattering technique, the propagation loss of the waveguide is 1.82 dB/cm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 203001 (2015)
Research on Microstructure and Properties of Fiber Laser Repairing ZM5 Magnesium Alloy Thin-Walled Casting
Chen Hong, Li Zhuguo, Yao Chengwu, and Wu Yixiong
In order to repair thin-walled castings of ZM5 magnesium alloy, the parameters for fiber laser welding are determined by dilution rate and weld-surface angle. Scanning electron microscope (SEM) and X-ray diffraction (XRD) are adopted for microstructure observation and analysis of chemical composition while tensile testIn order to repair thin-walled castings of ZM5 magnesium alloy, the parameters for fiber laser welding are determined by dilution rate and weld-surface angle. Scanning electron microscope (SEM) and X-ray diffraction (XRD) are adopted for microstructure observation and analysis of chemical composition while tensile tests are carried out for evaluation of mechanical properties. It′s demonstrated that the relationship between dilution rate and weld-surface angle is linear dependence. The fiber laser welding layer consists of tiny equiaxed dendrites with the average grain diameter of 15 to 20 μm which is 1/4 of ZM5 base. The base structure of welding layer is α - Mg phase, and the eutectic Mg-Al phase, β - Mg17Al12 mainly, is even dispersed along the grain boundary of welding layer. Shown in tensile tests, quasi-cleavage fracture occurred in fiber laser welding layer, which achieves higher strength and toughness than those of the brittle-fractured base metal. Thus thin-walled castings of ZM5 magnesium alloy are so well repaired by fiber laser that production quality and efficiency are greatly improved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 203002 (2015)
Process Optimization and Design of Fiber Laser Cutting Aluminium-Lithium Alloy
Zhang Wei, Li Guozhu, Wang Chunming, Hu Xiyuan, and Yan Fei
Aluminium-lithium alloy is the ideal material in aerospace industry for its lightweight and high strength. 2 mm aluminium-lithium alloy is used for laser cutting by employing 1 kW fiber laser to improve its cutting quality. The effect of the process parameters on the quality of laser cutting, such as defocus, gas pressAluminium-lithium alloy is the ideal material in aerospace industry for its lightweight and high strength. 2 mm aluminium-lithium alloy is used for laser cutting by employing 1 kW fiber laser to improve its cutting quality. The effect of the process parameters on the quality of laser cutting, such as defocus, gas pressure, laser power and cutting speed is studied. Cutting qualities under continuous laser mode and pulsed laser mode are compared. The results reveal that pulsed laser mode can achieve a better cutting quality. Optimization of technological parameters is performed by using the visual analysis of orthogonal experiment, the analysis of variance and the analysis of signal to noise ratio. Finally, the good quality with 0.087 mm slag thickness and 4.81 μm surface roughness can be obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 203003 (2015)
Study on the Mechanism of Root Humping of Laser Welding with High Power Fiber Laser
Chen Genyu, Xia Hailong, Zhou Cong, Li Shichun, and Li Changzou
In the process of high power fiber laser welding of SUS 304 stainless steel plate, the dynamic pool endures imbalanced force and is very unstable. The pool is prone to droping down. The pool is droping down, which makes a flow accumulation at the bottom of the specimen, and a root humping forms. By using highspeed cameIn the process of high power fiber laser welding of SUS 304 stainless steel plate, the dynamic pool endures imbalanced force and is very unstable. The pool is prone to droping down. The pool is droping down, which makes a flow accumulation at the bottom of the specimen, and a root humping forms. By using highspeed camera and“sandwich”new welding method, the pictures of the flow of the molten metal from different angles are taken and the longitudinal keyhole and the dynamic pool are observed. The results show that the molten metal flow is not continuous in the keyhole, the moving downward shelf on the front of the keyhole wall and the pressure of metallic vapor inside the keyhole lead to a plurality of droplet in the bottom of the pool. The surface tension and the flow of melt pool cause the backward flow of the molten metal. With the accumulation of molten metal, the root humping is formed. The root humping influences the flow state of melt pool, which results in the undercut on the weld surface..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 203004 (2015)
Effect of Laser Welding Heat Input on Microstructure and Properties of 26Cr-3.5Mo Ferritic Stainless Steel
Liu Lala, Hu Shengsun, Shen Junqi, Ma Li, and Wei Xin
Continuous laser welding is conducted to investigate the effect of heat input (HI) on the microstructure and mechanical properties of 26Cr-3.5Mo ferritic stainless steel. The optical microscope (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectrometer (EDS) are Continuous laser welding is conducted to investigate the effect of heat input (HI) on the microstructure and mechanical properties of 26Cr-3.5Mo ferritic stainless steel. The optical microscope (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectrometer (EDS) are used to observe the microstructure and the precipitates in the weld. And the mechanical properties are tested by the microhardness tester and the tensile tester. The result show that there are fine equiaxed grains at the center of the weld, and with the increase of the laser welding heat input, the width of equiaxed crystal zone increases, but the proportion of equiaxed crystal zone to the weld cross section increases firstly and then drops. The heat affected zone (HAZ) is narrow. Its width is 0.1~0.2 mm, and no obvious grain coarsening appeares in the HAZ. The HAZ is soften and its microhardness is lower than that of the weld and the base metal. The tensile strength of the welded joint is close to that of the base metal. But the percentage elongation of the welded joint after fracture is less than that of the base metal and decreases with the increase of the laser welding heat input..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 203005 (2015)
Weld Profile Prediction and Process Parameters Optimization of T-joints of Laser Full Penetration Welding via Response Surface Methodology
Chu Zhentao, Yu Zhishui, Zhang Peilei, Lu Qinghua, Li Shaowei, and Ma Kai
In order to predict weld profile of T- joints and optimize the process parameters of the laser full penetration welding, the statistical models between parameters and the weld bead geometry of T- joints are established using response surface methodology. Then the analysis of variance is checked and these mathematical mIn order to predict weld profile of T- joints and optimize the process parameters of the laser full penetration welding, the statistical models between parameters and the weld bead geometry of T- joints are established using response surface methodology. Then the analysis of variance is checked and these mathematical models are validated. Based on this model, effects of different process parameters on the weld profile are investigated, the process parameters are optimized, and the weld profile is predicted. The results indicate that the proposed models predict the responses adequately and the predicted values are consistent with experimental results. The optimum welding conditions are found that it can reduce the heat input about 27%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 203006 (2015)
Microstructures and Properties of Ultra-Narrow-Gap Multi-Pass Welded Joint of 50 mm Turbine Rotor Steel by Laser Welding with Filler Wire
Zhao Yong, Wang Qingzhao, Huang Jian, and Wu Yixiong
A type of groove targeted on ultra- narrow- gap multi- pass welding is designed and 50 mm thick 30Cr2Ni4MoV turbine rotor steel is welded by CO2 laser welding with filler wire based on the groove. After welding process, the microstructures of different zones of joint are observed and analyzed. The tensile test, bendingA type of groove targeted on ultra- narrow- gap multi- pass welding is designed and 50 mm thick 30Cr2Ni4MoV turbine rotor steel is welded by CO2 laser welding with filler wire based on the groove. After welding process, the microstructures of different zones of joint are observed and analyzed. The tensile test, bending test and measurement of microhardness are conducted to evaluate the properties of joint. The results show that the joint of 50 mm thick 30Cr2Ni4MoV turbine rotor steel has fine appearance without defect under the optimized parameters of ultra- narrow- gap multi- pass laser welding with filler wire. The middle zone of weld consists of a mass of acicular ferrite and a few of granular bainite and it shows good impact toughness. The surface layer of weld consists of martensite and a few of granular bainite and its impact toughness decreases a little. The fractures occurre on the base metal of tensile test specimens. The peak value of microhardness is achieved in the coarse grain zone in heat affected zone (HAZ) of surface layer of weld and the microhardness in weld is much lower than that in HAZ..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 203007 (2015)
Experimental Research on Fiber Laser Radial Sharpening of Resin-Bonded CBN Grinding Wheels and Grinding Characteristics
Chen Genyu, Zhou Xingcai, Zhou Cong, Deng Hui, Zhang Yong, and Chen Jun
Using a fiber laser to explore the key parameters of laser radial sharpening the resin-bonded cubic boron nitride (CBN) grinding wheels, a systematic research is carried out, which consists of the test of pulse overlap rate of optical fiber laser ablating resin-bonded wheels, optical fiber laser ablating resin-bonded wUsing a fiber laser to explore the key parameters of laser radial sharpening the resin-bonded cubic boron nitride (CBN) grinding wheels, a systematic research is carried out, which consists of the test of pulse overlap rate of optical fiber laser ablating resin-bonded wheels, optical fiber laser ablating resin-bonded wheels and optical fiber laser ablating resin- bonded CBN grinding wheels. The results, which have been testified by grinding experiments, show that the best pulse overlap rate is 30% ~50% , the best single pulse laser power density is distributed in the range of 5×107~7.5×107 W/cm2, the sharpening depth with a good performance is 39 μm , surface roughness of workpiece is 0.789 μm . The narrow and shallow traces of grinding are obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 203008 (2015)
Laser Physics
Calculation of Power Spectral Density of Beam Modulation Induced by Plasma Scalds
Guo Meng, Li Dawei, Wu Jianbo, Wang Hu, He Jun, Wang Yueliang, Chai Yingjie, and Fu Yanyan
The 1064 nm high reflectors are prepared by e-beam deposition, and via laser conditioning with raster scanning on certain areas, plasma scalds are formed on the surface. The beam quality testing system is built. The spatial intensity distribution of laser beam reflected by the samples with or without plasma scalds is rThe 1064 nm high reflectors are prepared by e-beam deposition, and via laser conditioning with raster scanning on certain areas, plasma scalds are formed on the surface. The beam quality testing system is built. The spatial intensity distribution of laser beam reflected by the samples with or without plasma scalds is recorded. The power spectral density of laser beam is calculated with periodogram method. The results indicate that the peak of the power spectral density corresponds to the peak intensity of the transmitted beam which is modulated by plasma scalds. Therefore the modulation of transmitted laser beam can be analyzed and characterized using the power spectral density calculated from the distribution of the laser beam..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 202001 (2015)
Dynamic Characteristics of Semiconductor Ring Laser with High Bias Current
Xue Pingping, Yang Lingzhen, Zhang Jianzhong, and Zhang Zhaoxia
The dynamic characteristics of semiconductor ring laser (SRL) with high bias current are numerically investigated, the bifurcation diagrams of different feedback coefficients, bias currents and delay time are displayed. The detailed process states demonstrate that the chaos paths with different parameters are differentThe dynamic characteristics of semiconductor ring laser (SRL) with high bias current are numerically investigated, the bifurcation diagrams of different feedback coefficients, bias currents and delay time are displayed. The detailed process states demonstrate that the chaos paths with different parameters are different. The results show that the chaos generated by SRL with high bias current has broad bandwidth characteristic. The influences of parameters on the bandwidth of chaos are also studied. It is found that the widest bandwidth is about 18 GHz when the feedback coefficient is 0.5..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 202002 (2015)
Exploring Femtosecond Laser Plasma to Reduce Drag of Hypersonic Vehicle
Fu Ning, Xu Degang, Zhang Guizhong, and Yao Jianquan
It is reported that femtosecond-duration laser pulse can be deployed to reduce drag for blunt-body vehicle in high- Mach flow field of air by generating laser plasma and shockwave. The interaction of plasma shockwave induced by femtosecond-duration laser pulse and bow shock over the head of the blunt-body vehicle is inIt is reported that femtosecond-duration laser pulse can be deployed to reduce drag for blunt-body vehicle in high- Mach flow field of air by generating laser plasma and shockwave. The interaction of plasma shockwave induced by femtosecond-duration laser pulse and bow shock over the head of the blunt-body vehicle is investigated numerically in the flow field of 30 km apart from the surface of the earth at Mach number of 5 and the mechanism of deploying the femtosecond laser plasma to reduce the drag of the vehicle is analyzed. The Navier- Stokes equations are exploited to compute the drag reduction for different femtosecond laser energies. The present numerical experiment proves that the femtosecond laser pulse has a better drag reduction effect than the nanosecond laser pulse under the same condition. When the femtosecond laser energy is 0.06 mJ, the femtosecond laser plasma can reduce the drag by 98%. And the higher the energy of femtosecond laser pulse, the higher the drag reduction ratio and the longer the time of low drag. Deploying three femtosecond laser energy point to reduce the drag of hypersonic vehicle is much more obviously. This energy-deposition mode can improve the optimum drag reduction ratio and save the laser energy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 202003 (2015)
Description and Evaluation of Beam Quality of Single Emitter Diode Laser Based on Beam Parameter Product
Niu Ben, Wang Baohua, Guo Weirong, Qu Yan, Wang Lirong, Zhao Yaping, Liu Yannan, and Lin Xuechun
Considering characteristics of beam output from output single emitter diode laser, beam width is described using 1/e2 maximum, power in bucket and second moment. The beam parameter product (BPP) in various definitions based on the hyperbolic fitting method with approximation of Gaussian beam can be obtained. The calculConsidering characteristics of beam output from output single emitter diode laser, beam width is described using 1/e2 maximum, power in bucket and second moment. The beam parameter product (BPP) in various definitions based on the hyperbolic fitting method with approximation of Gaussian beam can be obtained. The calculated BPPs of the beam from a single emitter diode laser are compared with the BPP of fiber with core diameter of 105 μm and numerical aperture of 0.2. The side mode increases gradually with increasing injection current, leading to deterioration of the beam quality, and reduces the coupling efficiency. As the injection current increases from 1 A to 13 A, the coupling efficiency decreases from 96.5% to 88.8% . Therefore, the beam width defined by the second moment is an accurate method for the description and evaluation the beam quality of single emitter diode laser based on BPP..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 202004 (2015)
Research on Route Optimization for Laser Beam Alignment at Target Area of an ICF Laser Facility
Cheng Ningbo, Li Fuquan, Feng Bin, Jia Huaiting, Xiang Yong, and Wei Xiaofeng
To reduce the total time for aligning all laser beams of an inertial confinement fusion (ICF) laser facility at the target area, an alignment route optimization method is for the alignment method that based on the invariant sub-area configuration of the alignment sensor. The goal is to minimize the sum of the angle disTo reduce the total time for aligning all laser beams of an inertial confinement fusion (ICF) laser facility at the target area, an alignment route optimization method is for the alignment method that based on the invariant sub-area configuration of the alignment sensor. The goal is to minimize the sum of the angle displacements of those reflecting mirrors which make contributions to the total alignment time. It can be implemented by optimizing the angle between the center of the preparative sub-area and that of the target sub-area. The optimization process is demonstrated through an example that one configuration of the final optics assemblies is considered and the expected aligning position is at the center of the target chamber. The estimations of the total alignment time show that the proposed method results in a much shorter time compared with the common serial alignment method. If the distance between the center of the preparative sub-area and the center of the target sub-area is 1 mm, the total time is reduced to 0.518 times of that adopting a common serial alignment method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 202005 (2015)
Research on a Method of Radiation-Resistant RLG Readout System
Li Long, Ding Xiaokun, Chen Linfeng, Han Zonghu, and Yan Jizhong
In order to improve the adaptability of ring laser gyro (RLG) in the outer space environment, a method about RLG output system based on Fresnel lens is proposed. After being converged by the Fresnel lens, the RLG′ s clockwise and anticlockwise beams forge a new array of fringe patterns in front of the focal plane, wherIn order to improve the adaptability of ring laser gyro (RLG) in the outer space environment, a method about RLG output system based on Fresnel lens is proposed. After being converged by the Fresnel lens, the RLG′ s clockwise and anticlockwise beams forge a new array of fringe patterns in front of the focal plane, where the number of patterns does not change, but the size is significantly reduced. Compared with the ordinary convex lens, the Fresnel lens based RLG readout system may bring up advantages in the spherical aberration calibration and installing convenience. It is validated that compared with the traditional RLG readout system, this system can decrease the size of the beam spot down to less than 1% , enabling a smaller photodiode to be selected, and the radiation damage is significantly reduced, therefore the RLG′s adaptability of RLG in the outer space environment is improved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 202006 (2015)
Numerical Simulation of Electromagnetic flow, Temperature Field and Flow Field in Laser Molten Pool with Electromagnetic Stirring
Wang Wei, Liu Qi, Yang Guang, Qin Lanyun, and Xue Xiong
A new three-dimensional mathematical model describing the electromagnetic stirring in the laser remelting is developed. The method combining the finite element and finite volume is used to deal with coupling electromagnetic field with flow field and temperature field. The influence of electromagnetic field on temperatuA new three-dimensional mathematical model describing the electromagnetic stirring in the laser remelting is developed. The method combining the finite element and finite volume is used to deal with coupling electromagnetic field with flow field and temperature field. The influence of electromagnetic field on temperature field and flow field are analyzed. The results show that the electromagnetic force is distributed circumferentially at horizontal plane, the magnitude of the tangential force decreases from edge to center; Under the effect of rotating magnetic field, the temperature and temperature gradient in the molten pool are slightly reduced; Liquid in the molten pool tends to rotary motion, it is similar that the distribution of velocity field and electromagnetic force; The circulation in the longitudinal of molten pool increases, which is benefit for heat transfer of molten pool and accelerates cooling speed; The distributions of electromagnetic field and flow field are affected by the intensity of exciting current. It provides the theoretical reference for laser processing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 202007 (2015)
Grating Fabrication of 808 nm Distributed Feedback Semiconductor Laser by Holographic Photolithography
Liu Dandan, Wang Yong, Ye Zhen, Gao Zhanqi, Zhang Yu, and Wang Xiaohua
Second-order Bragg grating structure of 808 nm distributed feedback (DFB) semiconductor laser is designed and optimized. The grating fabrication process of 808 nm DFB semiconductor laser is introduced. The grating with a period of 240 nm is fabricated on GaAs substrate by holographic photolithography and wet etching. ISecond-order Bragg grating structure of 808 nm distributed feedback (DFB) semiconductor laser is designed and optimized. The grating fabrication process of 808 nm DFB semiconductor laser is introduced. The grating with a period of 240 nm is fabricated on GaAs substrate by holographic photolithography and wet etching. In the holographic photolithography system, mole grating and piezoelectric ceramic are used as fringe locked-in system to control optical path and lock fringes. Wet etching solution with 1:1:10 volume ratio of H3PO4, H2O2 and H2O is adopted to etch the grating for 30 s. Images of optical microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM) show that the grating has a period of 240 nm, duty cycle of 0.25, depth of 80 nm, with perfect surface morphology, good fringe continuity and uniformity..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 202008 (2015)
1.5 MW Peak Power, Fiber-Solid Hybrid Amplification MOPA Lasers
Lu Yunfeng, Wang Yi, Liu Bin, Zhang Xiang, Wang Chunhua, Ye Zhibin, Liu Chong, Xiang Zhen, and Chen Jun
High peak power, high stability laser beams with excellent beam quality are ideal choices for material manufacturing and processing. A semiconductor laser with repetition frequency of 120 kHz, pulse width of 220 ps, average power of 26 μW is used as seed source. The pre-amplifier consists of two fiber amplifiers. The pHigh peak power, high stability laser beams with excellent beam quality are ideal choices for material manufacturing and processing. A semiconductor laser with repetition frequency of 120 kHz, pulse width of 220 ps, average power of 26 μW is used as seed source. The pre-amplifier consists of two fiber amplifiers. The power amplifier consists of four stages end-pumped Nd:YVO4 solid amplifiers. The average power of final laser output is up to 39.2 W with peak power of 1.5 MW. By optimizing the crystal doping concentration, crystal temperature, the pump beam diameter and beam filling factor in each solid amplifier, the output beam with M2 factor of 1.3 is achieved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 202009 (2015)
Angular Characteristics of Pulse Laser Echo Signal in Participating Medium
Zhang Xusheng, Guo Liang, Liu Chunlong, and Chen Liheng
To improve the echo signal-to-noise ratio and temporal-spatial resolution of active detection systems further, the two- way transient radiative transfer model of ultrashort pulse laser in participating medium is established using Monte Carlo method. Based on the model above, the influence of medium properties and targeTo improve the echo signal-to-noise ratio and temporal-spatial resolution of active detection systems further, the two- way transient radiative transfer model of ultrashort pulse laser in participating medium is established using Monte Carlo method. Based on the model above, the influence of medium properties and target reflective characteristic on the angular characteristic of Gaussian pulse laser echo signal in isotropic scattering medium is analyzed. Research shows that the incident zenith angles of target echo signal have reached its steady state in optically thick medium, with the peak angle interval of 30°~40° and the energy concentration range of 30°~50° , but the temporal broadening characteristic is irrelevant to angle intervals; the spectral attenuation coefficient affects the energy attenuation and pulse width of echo signal strongly, but the scattering albedo embodies in the energy attenuation of post-echo signal mainly; high intensity pre-echo signal caused by specular reflection weakens, and the absolute difference of target echo signal is extremely small between specular reflection and diffuse reflection, with weaker relevance. The reference for gated-camera design selection and pulsed laser wavelength is provided..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 202010 (2015)
Materials and Thin Films
Experiment Investigation on Residual Stress of Nd:Glass Edge Cladding
Hu Junjiang, Men Tao, Wen Lei, Chen Youkuo, Chen Huiyu, Chen Jimeng, Tang Jingping, Wang Biao, Chen Shubin, Chen Wei, and Hu Lili
In order to decrease the reflectivity of amplified spontaneous emission, suppress parasitic oscillations, an edge cladding that absorbs the reflected or scattered light is required. The residual stress of the edge cladding is an important parameter for bonding. The influence factors on the residual stress birefringenceIn order to decrease the reflectivity of amplified spontaneous emission, suppress parasitic oscillations, an edge cladding that absorbs the reflected or scattered light is required. The residual stress of the edge cladding is an important parameter for bonding. The influence factors on the residual stress birefringence near the bonding interface are described in detail. The effects of fine annealing, polishing and bonding are investigated. The results indicate that the effects of the edge stress of samples on the residual stress near the bonded interface are in evidence; the poorer of polishing surface flatness makes, the larger birefringence near the cladding interface; and the low shrink percentage and modulus adhesive polymer have less impact for the residual stress near the interface..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 206001 (2015)
Effect of Annealing on Mechanical Properties of AZ31 Magnesium After Laser Shock Processing
Yang Genmei, Zhang Lingfeng, and He Huanju
The variation of mechanical properties and fracture morphology of AZ31 Magnesium alloy after laser shock processing (LSP) at different annealing states is investigated．The results show that the hardness of AZ31 Magnesium alloy decreases when the annealing temperature and holding time increase. When the holding time is The variation of mechanical properties and fracture morphology of AZ31 Magnesium alloy after laser shock processing (LSP) at different annealing states is investigated．The results show that the hardness of AZ31 Magnesium alloy decreases when the annealing temperature and holding time increase. When the holding time is 30 min, the tensile strength and elongation go up with the annealing temperature rises from 200 ℃ to 350 ℃ while decline quickly when the annealing temperature reaches to 400 ℃ ; when the annealing temperature is 350 ℃ , with holding time goes on, tensile strength reduces gradually but the elongation first increases and then decreases. The best annealing state is 350 ℃ and 30 min when the tensile strength and the elongation at break are 342 MPa and 18% , respectively. Different annealing treatments have apparent effect on the fracture morphology of AZ31 Magnesium alloy after LSP, it presents remarkable toughness fracture surface morphology when the annealing state is 350 ℃ and 30 min..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 206002 (2015)
Properties of Large Size N31 Nd:Phosphate Laser Glass Prepared by Continuous Melting
Tang Jingping, Hu Lili, Chen Shubin, Chen Wei, Wang Biao, Weng Zean, Xu Yongchun, Chen Youkuo, Zou Zhaosong, Hu junjiang, Wen Lei, and Li Shunguang
The continuous melting technology is reported. The 400 mm aperture N31 Nd:phosphate laser glass prepared from continuous melting technology is fabricated. The main properties of N31-35 glass have been disclosed. Its Nd3 + ion concentration is 3.47 (± 0.02)× 1020 cm-3. The refractive index at 1053 nm is 1.5336The continuous melting technology is reported. The 400 mm aperture N31 Nd:phosphate laser glass prepared from continuous melting technology is fabricated. The main properties of N31-35 glass have been disclosed. Its Nd3 + ion concentration is 3.47 (± 0.02)× 1020 cm-3. The refractive index at 1053 nm is 1.5336 ±0.0005. The absorption coefficients at 400 nm and 3000 cm-1, the laser wavelength loss at 1053 nm are 0.098 cm-1 and 0.83 cm-1, 0.13~0.15% cm-1, respectively. The PV value of transmitted wavefront is less than λ/3 at 633 nm. Its bulk damage threshold with 1053 nm, 3 ns pulse laser is larger than 40 J/cm2. The results indicate that the dehydration and platinum particle removing processes are very effective during the continuous melting..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 206003 (2015)
Influence of Error from Plume on Transmittivity During Laser Irradiating Carbon/Epoxy Composites in Gas Flow
Peng Guoliang, Zhang Xianghua, Gao Yinjun, and Liu Weiping
The influence of plume on transmittivity during laser irradiating c-epoxy composites in gas flow is researched. A calculated model for transmittivity of plume is given by using Lambert- Beer theory. In the model, the length of optical paths is calculated by jet theory, density and velocity of plume can be got from the The influence of plume on transmittivity during laser irradiating c-epoxy composites in gas flow is researched. A calculated model for transmittivity of plume is given by using Lambert- Beer theory. In the model, the length of optical paths is calculated by jet theory, density and velocity of plume can be got from the simulation of laser ablating carbon/epoxy composites. The plume transmittivity during laser irradiating is computed by the model. The result is compared with the experiment, and it is confirmed that the model is reasonable. The influence of extrinsic parameters on laser transmittivity is calculated. The results indicate that when laser irradiation begins, thermal decomposition zone is on the material surface and it is easy for plume escaping from the zone, and transmittivity decreases to minimum value quickly. Then thermal decomposition zone moves to the interior and it is difficult for plume escaping from the zone because of low permeability, and transmittivity increases slowly. Higher laser intense decreases the minimum transmittivity and average transmittivity of the whole irradiation time; higher flow velocity can increase the transmittivity of the whole irradiation time; when total laser power is constant, bigger spot size can increase the minimum transmittivity and decrease average transmittivity of the whole irradiation time..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 206004 (2015)
Preparation and Research of Ce, Pr:YAG Fluorescent Transparent Ceramics Applied to White LED
Ni Yi, Wang Kai, Zhou Shengming, Chen Chong, Yi Xuezhuan, and Feng Yue
The CeO2, Al2O3, Y2O3, Pr6O11 powders in accordance with (Ce0.001PrxY0.999-x)3Al5O12 (x=0.001~0.005) are mixed and tableted. The Ce, Pr:YAG fluorescent transparent ceramics are obtained by sintering for 18 h in a vacuum induction furnace after cold isostatic pressing. The samples are subjected to X-ray diffraction (XRDThe CeO2, Al2O3, Y2O3, Pr6O11 powders in accordance with (Ce0.001PrxY0.999-x)3Al5O12 (x=0.001~0.005) are mixed and tableted. The Ce, Pr:YAG fluorescent transparent ceramics are obtained by sintering for 18 h in a vacuum induction furnace after cold isostatic pressing. The samples are subjected to X-ray diffraction (XRD) analysis and no other phase is founded except for the YAG phase. Emission spectra of the samples with different concentration of Pr3 + ions are tested and the red emission peaks of Pr3 + ions at 610 nm is founded. By changing the doping concentration of Pr3 + ions, the color temperature and color rendering index of white light are effectively adjusted. The experimental results show that when the atoms fraction of Pr3 + ions is 0.1% , the Ce, Pr:YAG transparent ceramics show preferable parameters with the luminous efficiency of 90 lm/W, the color temperature of 4905 K, the color rendering index of 80 and the color coordinates of (0.35, 0.41) under the injection current of 100 mA. The results of Ce, Pr:YAG have more advantages than those of traditional fluorescent materials in the color temperature and the color rendering index. So, it is expected to be applied in the field of indoor lighting..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 206005 (2015)
Analysis of Temperature and Damage Characteristics of HgCdTe Crystal on Repetition Frequency of CO2 Laser
Wang Tingfeng, Tang Wei, Shao Junfeng, Wang Rui, and Guo Jing
In order to further research damage mechanism of HgCdTe crystal irradiated by high repetition frequency CO2 laser. Temperature experiment of HgCdTe crystal irradiated by high repetition frequency CO2 laser is conducted, and temperature rising progress of HgCdTe crystal irradiated by different repetition frequency CO2 lIn order to further research damage mechanism of HgCdTe crystal irradiated by high repetition frequency CO2 laser. Temperature experiment of HgCdTe crystal irradiated by high repetition frequency CO2 laser is conducted, and temperature rising progress of HgCdTe crystal irradiated by different repetition frequency CO2 laser (1、5、10 kHz) are measured. Theoretical model of HgCdTe crystal irradiated by high repetition frequency CO2 laser is developed, and the impact of laser repetition frequency on temperature characteristic is analyzed. The impact of thermal stress on damage characteristic is analyzed basing on scanning electron microscope (SEM) damage morphology and the value of temperature rising and thermal stress calculated by ANSYS. The research results show that temperature of the crystal irradiated by high repetition frequency CO2 laser gradually rise with increasing of irradiation time, and thermal equilibrium should have been attained on the Hg0.826Cd0.174Te crystal when irradiation time is 10 s. When repetition frequency is more than 1 kHz, the temperature mainly depends on laser average power density，and doesn′ t depend on repetition frequency. The maximum thermal stress is 5 × 107 Pa when Hg0.826Cd0.174Te crystal surface melts，the value of which is less than the ultimate stress. The conclusions have a reference value for laser protection on high repetition frequency CO2 laser..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 206006 (2015)
Study and Fabrication of Blue Laser Fundamental Cavity Film in Fluorescence Microscope
Fu Xiuhua, Wu Guanqi, Liu Dongmei, Li Songyan, Zhang Jing, and Dong Li
The blue laser has significant meaning in the application fields of biological engineering, laser screen, laser medical technology, investigation, communication and many fields of science. The resonant cavity is an important component of laser, how to make it work effectively turns to be a major subject. Aimed at the oThe blue laser has significant meaning in the application fields of biological engineering, laser screen, laser medical technology, investigation, communication and many fields of science. The resonant cavity is an important component of laser, how to make it work effectively turns to be a major subject. Aimed at the operating requirements of blue laser cavity surface film, based on Nd:YVO4, Ta2O5、SiO2 are chosen as coating materials. The films are prepared by vacuum coating equipment and double ion beam assist deposition. Through technics feedback analysis to the test result by several simulation experiments, the electric field distribution is optimized, which can decrease the damage of thin- film from laser. The reason of extremum method cumulative error is described, as well as reasons of control differences of short wavelength range and long wavelength range. By analysising optical thickness caused by refractive index, adjust the tool factor. The filter coating with well- optical performance, low- absorb, and steady- chemical properties is prepared, which satisfy the operating requirements of blue laser..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 207001 (2015)
Structure Optimization of Retroreflective Sheeting Based on Laminae Combination Technique
Luo Han, and Yuan Changying
Compared with the traditional glass beads embedded type membrane structure, cube corner type membrane structure has higher retroreflection coefficient. It is the foundation of designing and producing diamond grade retroreflective film. However, the entrance angle of cube corner type retroreflective sheeting is limited,Compared with the traditional glass beads embedded type membrane structure, cube corner type membrane structure has higher retroreflection coefficient. It is the foundation of designing and producing diamond grade retroreflective film. However, the entrance angle of cube corner type retroreflective sheeting is limited, and the retroreflection coefficient is anisotropic, these problems will affect the using effect of retroreflective sheeting. The new solution for the above problems has been studied. Based on ray tracing technology and the basic theory of optics, a simulation model is built to analyze the retroreflection performance of cube corner retroreflective film. For laminae combination technology, width/thickness ratio and apex decentration are studied. It is found that the retroreflection performance varies dramatically with these two parameters. Through setting appropriate width/thickness ratio as well as apex decentration distance of cube corner elements, the effective incident angle range is increased and the anisotropy of retroreflection coefficient is weakened. These conclusions have certain guiding significance for the optimization design of the cube corner retroreflective sheeting..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 207002 (2015)
Measurement and Metrology
Analysis of Effect of Numerical Aperture of Illumination Objective Lens on Quality of Wavefront Diffracted by Tiny Pinhole
Qi Yuejing, Lu Zengxiong, Yang Guanghua, Liu Chengtao, and Peng Zhuojun
High quality spherical wave, which is generated by the pinhole diffraction, is the core for the calibration of the Shack-Hartmann wavefront sensor (SHWS) with high-accuracy. The diffraction of the tiny pinhole under the illumination of the excimer laser with wavelength of 193 nm is calculated based on finite-differenceHigh quality spherical wave, which is generated by the pinhole diffraction, is the core for the calibration of the Shack-Hartmann wavefront sensor (SHWS) with high-accuracy. The diffraction of the tiny pinhole under the illumination of the excimer laser with wavelength of 193 nm is calculated based on finite-difference timedomain (FDTD) method. The finite thickness and real conductivity of the pinhole are considered. The effect of numerical aperture (NA) of the illumination objective lens on the quality of the wavefront diffracted by the tiny pinhole is analyzed. The diameter of the tiny pinhole and the NA of the illumination objective lens needed to calibrate the SHWS with high accuracy are determined. The calculation and analysis show that, to obtain the wavefront whose quality meets the requirement of wavefront error measurement by using SHWS method with nanometer accuracy, the diameter of the tiny pinhole should be 200 nm and the NA of the illumination objective lens should be in the range of 0.6 to 0.75. In this situation, the RMS deviation of the wavefront diffracted by the tiny pinhole is 3.50×10-3 λ ; the intensity uniformity is 0.10; the transmission of the tiny pinhole is about 0.15..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 208001 (2015)
Research on Principle of Saft Dynamic Torque Measurement Based on Digital Industrial Photogrammetry Technology
Zi Xinyun, Geng Shuai, Zhao Shufan, Wang Ying, and Qin Wanjun
Based on the digital speckle correlation calculation and motion shaft surface matching method, a new method which uses dual cameras to measure dynamic torque of rotating shaft directly is put forward. Two industrial cameras are used to gather shaft surface image sequence which is used as reference images without torqueBased on the digital speckle correlation calculation and motion shaft surface matching method, a new method which uses dual cameras to measure dynamic torque of rotating shaft directly is put forward. Two industrial cameras are used to gather shaft surface image sequence which is used as reference images without torque, at both sides. Then surface strain images of rotating shaft under the action of torque are synchronously collected. Motion shaft surface matching method is used to search the corresponding reference images of strain images, and the full-pixel correlation calculation and the sub-pixel displacement calculation of gradient method are performed on two channels of strain and the reference images, respectively. The torsional angular displacement of both ends and the shaft torque are calculated. In order to verify measuring precision of the method, software Ansys is used to calculate torsional displacement of shaft. Compared with the proposed method, the error is 1.39% , which shows high consistency. Bench experiments under different rotational speeds and torque are done, and compared with standard sensor measurements, the error is 1.4% ~5.3%. Experimental results show that the torque measurement system based on digital industrial camera has high precision. The system structure is simple, and it overcomes the shortcomings of traditional methods, such as complexed installation, susceptible to interference. It is suitable for dynamic torque measurement of shaft..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 208002 (2015)
Analysis of Pose Selection on Binocular Stereo Calibration
Xie Zexiao, Lu Wenjuan, Wang Xiaomin, and Liu Jingxiao
In order to improve the stability and precision of binocular calibration based on two- dimensional plane target, the influence of pose selection on calibration is emphatically analyzed from homography matrix perspective. Then three properties are proposed to regulate calibration poses, which point out respectively, to In order to improve the stability and precision of binocular calibration based on two- dimensional plane target, the influence of pose selection on calibration is emphatically analyzed from homography matrix perspective. Then three properties are proposed to regulate calibration poses, which point out respectively, to avoid all poses of translating and rotating target only in its own plane and the parallel pose between target and image plane. On the basis of three properties, a strategy to select poses of binocular calibration called five poses set calibration is presented. Experimental results demonstrate that three properties have high application value, which is beneficial to ensure accuracy of calibration, and only if no less than three images are acquired in every pose set, five poses set calibration can reach high calibration reliability and accuracy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 208003 (2015)
Two-Dimensional Virtual Grating Phase Shifting Moire Fringe Method of Phase Extraction
Chen Chen, Liu Ke, Li Yanqiu, and Wang Hai
The most useful traditional technique to extract the phase information from a two-dimensional (2D) interferogram is fast fourier transformation (FFT), which is proven to be sensitive to noise. The virtual grating phase shifting Moire fringe method has not only a good anti-noise characteristic but also a good extractionThe most useful traditional technique to extract the phase information from a two-dimensional (2D) interferogram is fast fourier transformation (FFT), which is proven to be sensitive to noise. The virtual grating phase shifting Moire fringe method has not only a good anti-noise characteristic but also a good extraction accuracy. Based on the research of processing the one-dimensional interferogram, a new two-dimensional virtual grating phase shifting Moire fringe method which can process the two-dimensional interferogram is proposed, which can extract the phase information by generating a 2D virtual grating containing special phase-shift amount. The simulation result between the FFT method and the new method shows that in the case of the interferogram without noise, the relative reconstruction error using the FFT method and the proposed method are 5.52% and 3.46% , respectively. However, the new method has an obvious advantages over the FFT method gradually while the noise increases. Processing the 2D interferogram obtained by the 2D lateral shearing interferometer null test system developed by our research group, the root mean square experiment results of the FFT method and the proposed method are 0.0053 λ and 0.0037 λ (λ = 632.8 nm) , respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 208004 (2015)
Access Control Algorithm of Data Relay Satellite with Microwave and Laser Hybrid Links based on Jobs Type
Zhao Weihu, Zhao Shanghong, Zhao Jing, Deng Boyu, Dong chen, Li Yongjun, and Dong Yi
According to oversubscribed requests problem of user satellite for data relay access, the types of job and the features of the multi-constraint of access control are studied. A constraint satisfaction model is established based on it. The link access flexibility and jobs′ conflict set are set according to the jobs typeAccording to oversubscribed requests problem of user satellite for data relay access, the types of job and the features of the multi-constraint of access control are studied. A constraint satisfaction model is established based on it. The link access flexibility and jobs′ conflict set are set according to the jobs type, valid time and priority setting. To maximize the number of priority weighted jobs, an access control algorithm of data relay satellite with microwave and laser hybrid links is introduced. The double-layer optimization hybrid links algorithm is based on the jobs type and adaptive small-window ant colony algorithm. The sequence of jobs access and the selection of relay satellite link are set as optimization objects. Simulation results show that the model can realize multi-type jobs access control efficiently. The proposed double-layer optimization algorithm is better than the single-layer optimization, and it is with a faster convergence speed and better global optimization ability. So the proposed algorithm can effectively solve the multi-type jobs with multiconstraint, multi-antenna and multiple relay satellites access control problem..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 208005 (2015)
Design of Graphite-Cone-Absorption-Cavity Absolute Energy Meter for High Energy Laser
Wei Jifeng, Jiang Zhixiong, Lu Fei, Zhou Shan, Chang Yan, Hu Xiaoyang, Sun Liqun, Zhang Kai, and Zhang Wei
There is great temperature gradient in the absorber of the high energy laser energy meter for a long time, which results in great difficulties in measuring the real temperature of the absorber. In this situation, the accuracy of the energy meter is affected by the heat specific of the material, the responsibility of thThere is great temperature gradient in the absorber of the high energy laser energy meter for a long time, which results in great difficulties in measuring the real temperature of the absorber. In this situation, the accuracy of the energy meter is affected by the heat specific of the material, the responsibility of the temperature sensors and the heat loss. The temperature field of the absorber is simulated, and then a method that multiple discrete thermocouple sensors are used to measure the temperature rise of absorbers is introduced. The average temperature of each small segment in the absorber can be exactly obtained by controlling the distance of the adjacent thermocouples and the depth of the thermocouples, so as to calibrate the heat specific and the responsibility of the temperature sensors. The measurements are taken to decrease the rate of the heat loss and the heat loss can also be calibrated after obtaining the real temperature distribution and the time of the thermal equilibrium. The research on the absorption coefficient is facilitated with the ray tracing method. The absorption coefficients with the parameters of the real beams and the real absorption cavity are calculated and the measurement results are calibrated. According to the uncertainty of the each process, the estimate of the measurement uncertainty of the laser energy meter is 5.8％ (k=2), and the rationality of the measurement uncertainty is verified with the comparison method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 208006 (2015)
Optical Communication
Multi-Dimensions Encoding Scheme for Visible Light Communication System
Kang Ye, and Ke Xizheng
In order to improve the spectrum utilization in visible light communications (VLC), a new multidimension encoding scheme is proposed and its encoding principle and performance are analysed. A VLC system to transmit high quality video and audio signal is demonstrated. The system uses RGB light emitting diode (LED) as soIn order to improve the spectrum utilization in visible light communications (VLC), a new multidimension encoding scheme is proposed and its encoding principle and performance are analysed. A VLC system to transmit high quality video and audio signal is demonstrated. The system uses RGB light emitting diode (LED) as source, which is encoded by the multi-dimension encoding scheme with 16 pulses position modulation (16-PPM) as a base modulation, and achieves the video stream communication in the distance of 3.0 m and at the rate of 1.5 Mbit/s . The results show that the method can take fully the advantage of the vast frequency resources provided by light, improve the channel capacity and provide the possiblity of high-speed communication systems..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 205001 (2015)
All Optical Frequency Multiplication Technology Based on Terahertz Optical Asymmetric De-Multiplexer
Jian Yangtian, Wang Zhi, Lin Qing, Sun Zhenchao, and Wu Chongqing
Terahertz optical asymmetric de- multiplexer (TOAD) is one of the key devices for all- optical signal processing with its fast response, good integration and stability. A scheme for all optical frequency multiplication is proposed based on the TOAD. The switch characteristics of the TOAD are discussed with simulations Terahertz optical asymmetric de- multiplexer (TOAD) is one of the key devices for all- optical signal processing with its fast response, good integration and stability. A scheme for all optical frequency multiplication is proposed based on the TOAD. The switch characteristics of the TOAD are discussed with simulations for bimodal output on the leading and tailing edges of the clock pulse as control, in addition with the dependence on some factors of the TOAD, such as energy of control pulse, window of TOAD, carrier recovery time. Based on the bimodal output effects, the all- optical frequency doubling, tripling and quadrupling are simulated, and the frequency doubling of the clock is implemented with simulations and experiments for 200 Mb/s and 1 Gb/s clocks..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 205002 (2015)
Wireless Positioning Algorithm Based on Light Emitting Diode Lights and Camera Calibration
Bai Bo, Tian Hua, and Li Xiaobo
Considering the poor precision performance and high cost of the current wireless positioning algorithms, and combined with light emitting diode (LED) lights based visible light communication (VLC) system, a new wireless positioning algorithm based on camera calibration and with high precision is proposed, in vew of camConsidering the poor precision performance and high cost of the current wireless positioning algorithms, and combined with light emitting diode (LED) lights based visible light communication (VLC) system, a new wireless positioning algorithm based on camera calibration and with high precision is proposed, in vew of camera distortion effect, non- isotropic, assembly deviation on captured pictures. This algorithm could calculate the receiver′ s position, as well as its posture, with the position relationship to the LEDs, and LED position generated through the VLC system, and improve the anti- interference performance of VLC system through tracking and pointing. Experimental results show that this algorithm could achieve a positioning precision of a centimeter level, and generate relatively accurate posture information less than 5°. In addition, the bit error rate of the VLC with tracking and pointing performs two orders of magnitude better than the one with merely tracking, and improves the anti-interference capability and stability of the VLC system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 205003 (2015)
Research on All-Fiber Narrow Bandwidth Picosecond Pulse Seed Source for CARS Excitation Source
Jiang Junfeng, Guo Honglong, Liu Tiegen, Liu Kun, and Wang Hui
A picosecond pulse seed source with narrow bandwidth, low repetition rate and dispersionmanagement-free characteristics is studied. The intracavity pulse evolution is analyzed through numerical simulation. The influences of the cavity length and the fiber Bragg grating (FBG)′s bandwidth on the pulse stability and pulseA picosecond pulse seed source with narrow bandwidth, low repetition rate and dispersionmanagement-free characteristics is studied. The intracavity pulse evolution is analyzed through numerical simulation. The influences of the cavity length and the fiber Bragg grating (FBG)′s bandwidth on the pulse stability and pulse duration are investigated. Experiment setup is established to carry out the experimental research on the effect of cavity length and pump power. When the cavity length is 24.1 m, a stable optical pulse with 86 ps pulse duration is obtained successfully, the bandwidth and the repetition rate of which are 0.04 nm and 4.3 MHz, respectively. When the pulse is amplified for coherent anti-Stokes Raman scattering(CARS) spectrum detection, the theoretical spectral resolution can be 0.3 cm-1..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 205004 (2015)
All-Optical Wavelength Conversion Based on Parallel Dual-Pump for Polarization Multiplexing OFDM Signal in SOA
Lu Jia, Hu Yuanyuan, Liu Jianfei, Zeng Xiangye, and Gao Junping
The all-optical wavelength conversion (AOWC) based on parallel dual-pump for polarization multiplexing 16 quadrature amplitude modulation arthogonal frequency division multiplexing (16QAM-OFDM) signal in semiconductor optical amplifier (SOA) is theoretically analyzed and simulated. The theoretical analysis and simulatiThe all-optical wavelength conversion (AOWC) based on parallel dual-pump for polarization multiplexing 16 quadrature amplitude modulation arthogonal frequency division multiplexing (16QAM-OFDM) signal in semiconductor optical amplifier (SOA) is theoretically analyzed and simulated. The theoretical analysis and simulation results show that the polarization multiplexing 16QAM-OFDM signal can be received without crosstalk after AOWC by direct-detection, besides that several conditions which affect the AOWC conversion efficiency in this system are analyzed, such as frequency spacing of parallel pumps, SOA injection current, average power and the azimuth of optical signal. This simulation results also validate the correctness of theoretical analysis at the same time..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 205005 (2015)
Research on the Technique of Optical Trapping Semiconductor Quantum-Dots Based on the Evanescent Field of Tapered Optical Fiber
Shang Yana, Shi Qingpeng, Pang Fufei, Ni Qingyan, Chen Zhenyi, and Wang Tingyun
Based on the optical trapping micro-and nano-particles effect of the evanescent field, we propose to investigate the optical trapping technique for semiconductor quantum dots by using tapered optical fiber. With the laser at 980 nm wavelength as light source, the PbS quantum dots (QDs) are absorbed and deposited on theBased on the optical trapping micro-and nano-particles effect of the evanescent field, we propose to investigate the optical trapping technique for semiconductor quantum dots by using tapered optical fiber. With the laser at 980 nm wavelength as light source, the PbS quantum dots (QDs) are absorbed and deposited on the surface of the tapered fiber successfully. By optical pumping, the photoluminescence from the tapered fiber after trapping PbS QDs is observed, and a gain of 6.8 dB is obtained at 1550 nm wavelength band..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 205006 (2015)
Rapid Communications
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Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 219001 (2015)
[in Chinese]
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Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 219002 (2015)
Optical Design and Fabrication
Optical Design and Stray Light Analysis for Ultraviolet Board Width Off-Axis Four Mirrors Optical System
Zhu Yang, Zhang Xin, Wu Yanxiong, Zhang Jizhen, Shi Guangwei, and Wang Lingjie
To satisfy the far ultraviolet space imaging system with super wide field, larger relative aperture, miniaturized size and good stray light suppression, a method based on the inverse focal power allocation theory is applied to calculate the structure of all spherical surface reflective system. The relevant technical paTo satisfy the far ultraviolet space imaging system with super wide field, larger relative aperture, miniaturized size and good stray light suppression, a method based on the inverse focal power allocation theory is applied to calculate the structure of all spherical surface reflective system. The relevant technical parameters of all spherical off- axis optical system include focal length 12 mm, F number 3 and field of view 70° × 10° . Such a design will consider to eliminate stray light of optics and structure, analyze stray light and main sources. The modulation transfer functions (MTF) at the cutoff spatial frequency are larger than 0.7 at all fields and the point sources transmittance (PST) arrives to 4.2 × 107 which is far less than 5 × 105 when the evadable angle out of the field of view is 10° . Compared to other optical systems, the main advantage of this system is that it can achieve super wide field with compact structures, utilizes all spherical mirrors which largely decrease the cost of fabrication, and presents high level of stray light suppression..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 216001 (2015)
Spectroscopy
Spectral Characteristics of Non-Chain Pulsed Deuterium Fluoride Laser
Pan Qikun, Xie Jijang, Shao Chunlei, Wang Chunrui, Ruan Peng, Shao Mingzhen, Meng Fanjiang, Li Shiming, and Guo Jin
In order to explore the cascade effect of deuterium fluoride (DF) laser and the influence of working gas parameters on laser spectrum, the spectral characteristics of non-chain DF laser pumped by self-initiated volume discharge are studied. The pulse shapes of cascade lasing on P3(7) →P2(8) →P1(9) are measured by DF laIn order to explore the cascade effect of deuterium fluoride (DF) laser and the influence of working gas parameters on laser spectrum, the spectral characteristics of non-chain DF laser pumped by self-initiated volume discharge are studied. The pulse shapes of cascade lasing on P3(7) →P2(8) →P1(9) are measured by DF laser spectrum analyzer and HgCdTe photo detector, and it′ s found that the lasing line of P1(9) is initiated firstly, and P2(8) and P3(7) lines appeare 80~100 ns later. The number of laser lines and the relative energies are measured under different ratios and pressures of gas mixture, and 22 laser lines in the rang of 3.5~4.2 μm are attained. When the pressure ratio and total pressure of gas mixture (SF6 and D2) are 6:1 and 8.1 kPa, 25.9% of emitted energy is contained in the cascade lasing on P3(8) →P2(9) →P1(10). The results show that there exits cascade effect in multiline DF laser, and the extraction efficiency of laser gain with cascade output can be greatly increased by optimizing the parameters of gas mixture..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 215001 (2015)
Detection and Analysis of Oxytetracycline Content in Egg White Using Surface Enhanced Fluorescence
Zhao Jinhui, Yuan Haichao, Hu Qi, Hong Qian, Peng Yijie, and Liu Muhua
With silver nanoparticles (AgNPs) as the substrate of the surface enhanced fluorescence, the OTC-Eu-AgNPs-Egg white system has a strong fluorescent characteristic, and the detection and analysis of oxytetracycline content in egg white can be realized. Three dimensional fluorescence spectra of the OTC-Eu-AgNPs-Egg whiteWith silver nanoparticles (AgNPs) as the substrate of the surface enhanced fluorescence, the OTC-Eu-AgNPs-Egg white system has a strong fluorescent characteristic, and the detection and analysis of oxytetracycline content in egg white can be realized. Three dimensional fluorescence spectra of the OTC-Eu-AgNPs-Egg white system is analyzed, and 380 nm is selected as the best excitation wavelength. Effect of the addition amount of AgNPs and Eu3+, reaction time and metal ions on fluorescence intensity is investigated, and the addition amount of AgNPs and Eu3+ is determined as 0.25 mL and 0.01 mL, respectively. A prediction model for determination of oxytetracycline content in egg white is established by using least squares support vector regression (LSSVR) between 605 nm and 630 nm, and the determination coefficient (R2) and root mean squared error of prediction (RMSEP) are 0.9909 and 0.9079 mg/L, respectively. The results show that silver nanoparticle enhanced fluorescence of europium (III) combined with LSSVR can be used to detect the oxytetracycline residue in egg white..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 215002 (2015)
Research on Open-Path Detection for Atmospheric Trace Gas CO Based on TDLAS
Yao Lu, Liu Wenqing, Liu Jianguo, Kan Ruifeng, Xu Zhenyu, Ruan Jun, and Dai Yunhai
As a kind of important pollutant in atmosphere and hazard gas in coal mine or oil field, CO has to be monitored in real-time for the safety of daily life and industrial production. The R(6) absorption line of CO near 2334 nm, without interference of H2O absorption, is screened for a tunable diode laser absorption spectAs a kind of important pollutant in atmosphere and hazard gas in coal mine or oil field, CO has to be monitored in real-time for the safety of daily life and industrial production. The R(6) absorption line of CO near 2334 nm, without interference of H2O absorption, is screened for a tunable diode laser absorption spectroscopy (TDLAS) system, which is used to monitor the atmospheric CO by long optical path with direct absorption techniques. With the help of off-axis parabolic mirror, an optical path of 700 m is achieved by sending and receiving light on the same path. A miniaturized measuring control system of 120 mm × 100 mm × 25 mm with power consumption lower than 5 W integrating laser driver, spectral data acquisition and processing on a single board is developed. The CO and CH4 spectra are separated on host computer by means of nonlinear fitting. By analyzing the standard deviation of spectral data, it can be derived that the system has detection precision of 10-6 at 1 s respond time. A continuous atmospheric CO monitoring experiment is carried out and the results coincide well with the CO analyzer results, which proves feasibility of the instrumentation of this system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 2, 215003 (2015)
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