Journals >Chinese Journal of Lasers
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2012
Volume: 39 Issue s1
91 Article(s)
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Research Article
Focusing Technology Based on Zernike Polynomial for Large Aperture off-Axis Parabolic Collimator
Ma Shibang, Yang Hong, Yang Zhaojin, Guo Yu, and Kang Dengkui
Based on the corresponding relation of the fourth coefficient q4 from the Zernike polynomial and the focus item from the Seidel aberration, the value of the fourth coefficient q4 from the Zernike polynomial is used as the criterion of the focusing method for laser interferometer. The focusing method using the criterionBased on the corresponding relation of the fourth coefficient q4 from the Zernike polynomial and the focus item from the Seidel aberration, the value of the fourth coefficient q4 from the Zernike polynomial is used as the criterion of the focusing method for laser interferometer. The focusing method using the criterion is feasible and the result of focusing method is steady. Besides, the positive or negative of the q4 can be used to judge whether the piont of intersection of the spherical wave from the interferometer is in front of the focus plane or behind the focus plane of a large aperture off-axis parabolic collimator, which will guide the move direction. The focus plane of the large aperture off-axis parabolic collimator is confirmed by using this method. From the calibration experiment, It′s known that the focusing effect is perfect and the parallelism error of emissive beam from collimator is less than 0.22″..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 108014 (2012)
Laser Diode Driver Circuit Design and Improvement Based on the MOSFET
Ma Tianxiang, and Tian Xiaojian
Laser diode (LD) driver circuit,which is based on the metal-oxide-semiconductor field-effect transistor (MOSFET) and discharging capacitor, its performance mainly depend on the MOSFET. If the distributed parameter is not perfectly controlled, pulse current output is so distorted that it can not drive the LD.overshoot, Laser diode (LD) driver circuit,which is based on the metal-oxide-semiconductor field-effect transistor (MOSFET) and discharging capacitor, its performance mainly depend on the MOSFET. If the distributed parameter is not perfectly controlled, pulse current output is so distorted that it can not drive the LD.overshoot, even the ringing may occur. We design complementary output circuit to solve this problem, it provides faster pulse-off time, and restrains the overshoot and ringing. Experimental results show that the new circuit improves the output effectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 116001 (2012)
Design and Adjust for Optical Tweezers Based on Finite Conjugate Microscope Systems
Ren Hongliang, Ding Panfeng, and Li Xiaoyan
Optical tweezers, or single beam gradient force optical traps, are very suitable for micromanipulation with large spectrum of specimens in the diameter range from several nanometers to tens of micrometers. Optical path of optical tweezers based on finite conjugate microscope systems is analysed and calculated. The desiOptical tweezers, or single beam gradient force optical traps, are very suitable for micromanipulation with large spectrum of specimens in the diameter range from several nanometers to tens of micrometers. Optical path of optical tweezers based on finite conjugate microscope systems is analysed and calculated. The design of optical tweezers consists of laying out a trapping laser, a collimation lens, an inverted microscope with a high numerical aperture objective and a CCD camera. The optical trains are to maximize the convergence angle and to maintain the trap position while retaining the same degree of overfilling of the microscope entrance aperture. The formulations provide the basis for theoretical analysis of experimental alignment and adjustment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 116002 (2012)
Design of Continuous Phase Plates for Uniform Illumination on a Out-of-Focus Curved Surface
Huang Dequan, Wen Shenglin, Zhao Xi, Zhang Chao, Yao Xin, and Gao Fuhua
A new method of designing continuous phase plates (CPP) for beam smoothing has been studied. The new CPP is applied when the diffraction field is a out-of-focus and curved surface. The traditional Gerchberg-Saxton (GS) algorithm is improved. During algorithm′s each iteration, the out-of-focus plane is regarded as desigA new method of designing continuous phase plates (CPP) for beam smoothing has been studied. The new CPP is applied when the diffraction field is a out-of-focus and curved surface. The traditional Gerchberg-Saxton (GS) algorithm is improved. During algorithm′s each iteration, the out-of-focus plane is regarded as design goal instead of focal plane. And the objective function for compensating the impact of cuned surface is reansomcted. The simulation has proved that the new CPP can control the envelope of focal spot on the out-of-focus curved surface well and obtain high energy concentration, so the demand of the distribution continuity for beam smoothing element, good profile of the target beam and high energy concentration in inertial confinement fusion can be satisfied simultaneously by this algorithm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 116003 (2012)
Thermal Optimized Design of LED Headlamp Based on CFD
Hu Shuhong, Yu Guiying, and Cen Yichao
The paper focuses on the heat dissipation efficiency problem existed with LED automobile headlamps. Based on computational fluid dynamics, Ansys-icepak is used to build plug-in fin and cylindrical fin models for LED headlamp heat dissipation structures. During simulation and optimization, the model′s geometric parameteThe paper focuses on the heat dissipation efficiency problem existed with LED automobile headlamps. Based on computational fluid dynamics, Ansys-icepak is used to build plug-in fin and cylindrical fin models for LED headlamp heat dissipation structures. During simulation and optimization, the model′s geometric parameters are set as variables, highest temperature and mass are set as constraint functions, thermal resistance is set as objective function. The result indicates that under the same boundary condition with 85 ℃ initial temperature, the plug-in fin model has mass of 0.2756 kg, temperature rise of 12.52 ℃ and thermal resistance of 1.026 ℃/W, which is better than cylindrical fin model, and accords with the heat dissipation standard of LED headlamp. During design in headlamps, an input air grill and an outlet are arranged at the front bottom and upper back of the headlamp respectively, the opposite direction wind generated from the moving automobile is taken to strengthen internal convection. The results show that when velocity is 2 m/s in grade one, the temperature rise is less than 10 ℃, which reflects higher heat dissipation efficiency..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 116004 (2012)
Calibration Plate Design for Surface Defect Inspecting System
Liu Xu, Reb Huan, Chai Liqun, Chen Bo, Yang Yongying, and Gao Xin
A reference plate is designed to calibrate surface defects inspecting system. By using it, the defects inspecting system can detect surface defects accurately. The main uncertainty which would affect the system′s measuring accuracy is analyzed to find out the way of reducing it. Electron beam is used to transfer all thA reference plate is designed to calibrate surface defects inspecting system. By using it, the defects inspecting system can detect surface defects accurately. The main uncertainty which would affect the system′s measuring accuracy is analyzed to find out the way of reducing it. Electron beam is used to transfer all the design chart to mask plate, and the calibrate plate is produced by using the reactive ion beam etching. Every standard scratch′s actual dimension is measured by scanning electron microscope, and the measured dimension is used to calibrate the surface defects inspecting system. Experiments are performed to calibrate the surface defect inspecting system for large aperture optical components. The result shows that the scattering image is meet to geometrical image result when the dimension of scratch is greater than 45 μm, while it should be computed by calibrated results as the dimension of scratch is less than 45 μm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 116005 (2012)
Biomedical Photonics and Laser Medicine
Finite element simulation for laser-induced SAW propagation in tooth
Ling Yuan, Kaihua Sun, Zhonghua Shen, Xiaowu Ni, and and Yiping Cui
Laser ultrasonic technology, a noncontact nondestructive evaluation method, can be applied to evaluating the properties of human teeth. With a finite element method, this paper studies laser induced surface acoustic wave (LSAW) characteristics propagating in human teeth. Setting up a theory model for laser-introduced sLaser ultrasonic technology, a noncontact nondestructive evaluation method, can be applied to evaluating the properties of human teeth. With a finite element method, this paper studies laser induced surface acoustic wave (LSAW) characteristics propagating in human teeth. Setting up a theory model for laser-introduced surface acoustic wave (SAW) propagating in human incisors, it discusses the temperature field induced by laser irradiate in dental surface, as well as the effects of inhomogeneous enamel and early dental caries (white spot lesion) on LSAWs. Studies in this letter can provide a theoretical basis for nondestructive evaluation of human teeth with laser ultrasonic technology..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 104001 (2012)
Determination of Nitric Oxide on Cancer Cell Mitochondria Membrane Potential Based on Microplate Fluorescence
Huang Yimei, Yang Hongqin, Chen Jiangxu, Wang Yuhua, Zheng Liqin, and Xie Shusen
The effects of endogenous and exogenous nitric oxide on cancer cell mitochondrial membrane potential are studied by combining microplate fluorescence analyzer and special fluorescence probe rhodamine 123. Results show that the fluorescence intensity increases rapidly and keeps at a high level for a quite long period afThe effects of endogenous and exogenous nitric oxide on cancer cell mitochondrial membrane potential are studied by combining microplate fluorescence analyzer and special fluorescence probe rhodamine 123. Results show that the fluorescence intensity increases rapidly and keeps at a high level for a quite long period after nitric oxide donor is injected into the cells, while the fluorescence intensity of control group do not change significantly. Moreover, incubation with nitric oxide synthase inhibitor or nitric oxide donor for 24 hours prior rhodamine 123 loading can decrease or increase mitochondrial membrane potential, respectively. These results indicate that the increase of endogenous or exogenous nitric oxide can lift up the potential of mitochondrial membrane. It will be helpful to understand the role of nitric oxide in promoting cancer cell proliferation and metastasis at organelle level..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 104002 (2012)
Holography and Information Processing
Auto Defect Extraction of Steel-Cord Conveyor Belt
Fu Liqin, Wang Hongying, and Zhang Ziliang
A detection system based on hybrid of magnetic method and radiography imaging technique is adopted to detect the hidden causes of accidents and ensure the safe operation of steel-cord conveyor belt. It is necessary to implement auto defect extraction of X-ray image of steel-cord conveyor belt for the real-time performaA detection system based on hybrid of magnetic method and radiography imaging technique is adopted to detect the hidden causes of accidents and ensure the safe operation of steel-cord conveyor belt. It is necessary to implement auto defect extraction of X-ray image of steel-cord conveyor belt for the real-time performance of the whole detection system. This paper lays special stress on studying the auto defect extraction method taking connector stretch for instance. The malfunction images of steel-cord belts are denoised and trimed firstly to decrease useless data. Then the interference from steel-cord is reduced using horizontal gray differential method. Image binarization based on histogram as well as denoise algorithm based on area of continuous bright pixels are implemented to obtain the pure defect signal. Finally the position and size informations of defect are extracted. The experimental results evaluate the effectiveness of the algorithm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 109001 (2012)
Fast Detection of Expanded Target Based on Binary Robust Independent Elementary Features
Deng Li, Wang Chunhong, and Rao Changhui
In some opto-electrical imaging system for extended target, because the target is lack of local detail, using complex detector and high-dimensional descriptor not only brings the problem of weak discrimination of description, but also results in high sources occupation and slow calculation, lead to a hard process in reIn some opto-electrical imaging system for extended target, because the target is lack of local detail, using complex detector and high-dimensional descriptor not only brings the problem of weak discrimination of description, but also results in high sources occupation and slow calculation, lead to a hard process in real-time. A specialized algorithm is proposed with features from accelerated segment test (FAST) as the detector and binary robust independent elementary feature (BRIEF) as the descriptor, to solve the problems efficiently. In the meantime, because the BRIEF is sensitive to the changes of target, a process named major orientation constraint is employed which can improve the stability of feature recognition. Experiments are done and this new algorithm is compared to two widely used algorithms, speed-up robust feature (SURF) and scale invariant feature transform (SIFT). The result shows that our algorithm performs 5 times of SURF and 17 times of SIFT in speed, meanwhile the recognition accuracy is comparable to that of SURF. Hence this algorithm achieves fast object detection and stable tracking without decline of recognition accuracy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 109002 (2012)
High Accuracy Signal Processing Technology in Laser Doppler Velocimeter Based on Mixed Programming
Liu Fan, Jin Shilong, and Liu Jun
A new method of signal processing is proposed in this article in order to eliminate the noise interference and enhance the measurement accuracy of laser Doppler velocimeter (LDV). The least mean square (LMS) adaptive filter technology, the frequency spectrum zooming and frequency spectrum correction technology are applA new method of signal processing is proposed in this article in order to eliminate the noise interference and enhance the measurement accuracy of laser Doppler velocimeter (LDV). The least mean square (LMS) adaptive filter technology, the frequency spectrum zooming and frequency spectrum correction technology are applied in the signal processing system. Basic principle of LMS adaptive filter and frequency analysis algorithms were expounded first, then spectrum simulation of ideal sinusoidal signal and experiment test are studied based on these algorithms. The simulation and experiment results indicate that the LMS adaptive filter technology has effectively improved signal to noise ratio and minish the interference of noise; Resolution of frequency spectrum can be improved by frequency spectrum zooming technology and the accuracy of signal processing can be greatly improved by frequency spectrum correction technology. It can obviously increase the frequency spectrum resolution, and improve the measurement accuracy for 2~3 times..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 109003 (2012)
Research on Multispectral Imaging Based on Spectral Band Extension of Infrared Thermal Image
Han Shunli, and Zhang Peng
Multispectral imaging of the infrared target provides effective method for the study of infrared radiation characteristic. It has significant applications in many fields of detection technologies such as material identification, false-target discrimination, complex backgrounds suppression. Based on the blackbody radiatMultispectral imaging of the infrared target provides effective method for the study of infrared radiation characteristic. It has significant applications in many fields of detection technologies such as material identification, false-target discrimination, complex backgrounds suppression. Based on the blackbody radiation theory, a new spectral imaging method, which extends the spectral band of measured infrared image, is proposed. Firstly, the infrared thermal image is collected by the mid-wave infrared thermal imager (3～5 μm). The temperature value of different pixel of the thermal image is obtained by calculating the radiation. Then the corresponding radiation of the different pixels in the desired spectral band is acquired from the temperature through Planck formula. And finally the radiation data are quantified and represented as multispectral infrared images..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 109004 (2012)
Remote Sensing Images Fusion Algorithm Based on the Nonsubsampled Contourlet Transform
Yang Lixin, Yang Jiankun, Jia Hui, Qi Junli, and Huang Hongxi
In order to make the fused multispectral (MS) image keep the spectrum information of the original multispectral image as much as possible and improve the spatial resolution effectively, a novel image fusion algorithm based on the nonsubsampled contourlet transform (NSCT) and the multiresolution edge detection is proposIn order to make the fused multispectral (MS) image keep the spectrum information of the original multispectral image as much as possible and improve the spatial resolution effectively, a novel image fusion algorithm based on the nonsubsampled contourlet transform (NSCT) and the multiresolution edge detection is proposed. The advantages of NSCT and multiresolution edge detection are presented; The fusion rules of the high and low frequency subbands respectively based on multiresolution edge detection and direct substitution are devised; The QuickBird images have been fused with this new method. The simulation experimental results demonstrate that the method proposed could keep the spectral information and improve spatial resolution simultaneously, and work better than traditional wavelet and contourlet transform..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 109005 (2012)
New Smart Fast Search Method of Star Identification
Sun Jianming, Zhao Lin, and Zhou Weidong
The key of the star pattern identification algorithm is highly efficient identification with little time.In the past few decades, people committed to methods to search database, and indeed invented a large number of search methods. In order to save the time of searching the star map database, the technology of hierarchThe key of the star pattern identification algorithm is highly efficient identification with little time.In the past few decades, people committed to methods to search database, and indeed invented a large number of search methods. In order to save the time of searching the star map database, the technology of hierarchical classification of different stars is presented, meanwhile, uses this fast and accurate search method to propose new smart fast star identification algorithm. Desktop-based simulation results show that this star identification methods and database search methods with high accuracy and efficiency. The time complexity of searching star features via database is 0(n). In addition, because the quality of the star image determines accuracy of the star pattern recognition algorithm, a fuzzy edge detection technique is proposed to solve the problem of preprocessing images. This method has a great significance to noise cancellation, the star feature extraction and manufacture and match of database..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 109006 (2012)
Assessment Method of Fusion Image Quality in Wavelet Domain Structural Similarity
Zhang Yong, and Jin Weiqi
For the fusion image quality evaluation, the relationship between fusion image quality assessment and image quality assessment is analyzed, and the general expression of fusion image quality assessment is provided. Meanwhile, it is explained that the key of fusion image quality assessment is to construct the reference For the fusion image quality evaluation, the relationship between fusion image quality assessment and image quality assessment is analyzed, and the general expression of fusion image quality assessment is provided. Meanwhile, it is explained that the key of fusion image quality assessment is to construct the reference image that is inexistent actually. Based on the above analysis and the space domain structural similarity evaluation method, wavelet decomposes input source images and fusion image respectively and structure reference image wavelet coefficient is obtained based on the wavelet decomposition coefficient of input source images. Afterwards, by weighing different levels of wavelet frequency band according to the human eye sensation characteristics, the wavelet domain structural similarity metrics to the whole fusion image are created. Comparing the mutual information and space domain structural similarity evaluation method with the subjective assessment index using target detectable ability, detail resolvable ability and whole comfortable ability as a reference, experimental results show that wavelet domain structural similarity method agrees with human visual features and its objective results. It is more consistent with the subjective assessment results than traditional methods..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 109007 (2012)
Iterative Hard Thresholding Recovery Algorithm Based on Spectral Decorrelation Model
Kong Fanqiang, Ji Zhenxing, and Jing Qingfeng
According to the characteristic of hyperspectral images, a novel iterative hard thresholding (IHT) recovery algorithm based on spectral decorrelation model is proposed. In terms of apparent correlations between the image series, a spectral decorrelation model is established in iterative hard thresholding recovery algorAccording to the characteristic of hyperspectral images, a novel iterative hard thresholding (IHT) recovery algorithm based on spectral decorrelation model is proposed. In terms of apparent correlations between the image series, a spectral decorrelation model is established in iterative hard thresholding recovery algorithm. The spectral redundancies are removed in the measured data of current image by the model, and the decorrelation image data is much sparser, which can be reconstructed easily. Experimental results show that the proposed algorithm achieves improved reconstruction performance over IHT algorithms with the same measurement number..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 109008 (2012)
Laser Devices and Laser Physics
Recent Research and Development of Tilt-Tip Wavefront Control in Coherent Beam Combination of Fiber Lasers
Wang Xiong, Wang Xiaolin, Zhou Pu, Xu Xiaojun, and Shu Bohong
Coherent beam combination is an effective way to achieve high-power laser while maintain good beam quality. In coherent beam combination, the piston phase differences, tilt-tip wavefronts and filling factor of each beamlets have direct effects on the combined beam quality. The tilt-tip error of each beamlet have signifCoherent beam combination is an effective way to achieve high-power laser while maintain good beam quality. In coherent beam combination, the piston phase differences, tilt-tip wavefronts and filling factor of each beamlets have direct effects on the combined beam quality. The tilt-tip error of each beamlet have significant influence on coherent combination, so the tilt-tip control is of great significance. The main tilt-tip control instruments, including liquid crystal spatial light modulator, fast steering mirror and adaptive fiber collimator, are introduced detailedly. Advantages and disadvantages of different tilt-tip wavefront active control methods are analyzed. The development and perspective of tilt-tip wavefront control in coherent beam combination are reviewed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 101001 (2012)
Laser Manufacturing
Algorithm of Rapidly Generating Contour Line Based on Rapid Prototyping
Wan Chenghui, and Cheng Xiaojun
It is difficult to extract scattered point cloud feature lines directly due to its characteristic of mass and not topological. A contour generation algorithm for point cloud based on rapid prototyping is described. The approach is that point cloud layers to project onto the slice plane and transform to grid image. It eIt is difficult to extract scattered point cloud feature lines directly due to its characteristic of mass and not topological. A contour generation algorithm for point cloud based on rapid prototyping is described. The approach is that point cloud layers to project onto the slice plane and transform to grid image. It establishes line data structure to extract contour by calculating the domain connectivity. The list of the straight line is adopted to establish connectivity to solve the multi-connected domain problem; the point cloud in cell is compressed to solve the data redundancy and uneven distribution. Experiments show that this method of the contour line generated is rapid and effective..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 103001 (2012)
Current Research Status and Development Trends of Laser Welding
Shen Yifu, and Zhang Shenghai
With the improvement of laser beam quality and the increasing of laser power output, the percentage of deep penetration laser welding increases gradually in laser processing and welding field. The recent major research achievements of deep penetration laser welding have been summarized, meanwhile, its characteristics aWith the improvement of laser beam quality and the increasing of laser power output, the percentage of deep penetration laser welding increases gradually in laser processing and welding field. The recent major research achievements of deep penetration laser welding have been summarized, meanwhile, its characteristics and limitations have been discussed as well. And then many important advances have been analyzed and discussed in the field of deep penetration laser welding, such as the research of high power laser, stability of laser welding process, control of laser-induced plasma, auxiliary electromagnetic fields, laser-arc hybrid welding and so on. Finally, the development foreground of deep penetration laser welding in the future is prospected..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 103002 (2012)
Pre-ablation Pulse Laser-Inducted Breakdown Spectroscopy Technology for Enhanced Ablation and Emission Plasma
Zhai Yang, and Zhu Rihong
The alloy sample ablation using a welding torch normally can not meet the local thermal equilibrium (LTE) standardization due to a relatively low burning temperature, thus this will lead to some detection limits, such as full-noise signals in consecutive samples, matrix effect and a fluctuated and inaccurate electronicThe alloy sample ablation using a welding torch normally can not meet the local thermal equilibrium (LTE) standardization due to a relatively low burning temperature, thus this will lead to some detection limits, such as full-noise signals in consecutive samples, matrix effect and a fluctuated and inaccurate electronic temperature measurement, etc. A short-pulse laser (NdYAG) is brought in parallel to the sample surface and focused about 1 mm above it to form a pre-ablation spark for a few microseconds before the welding torch, which is focused orthogonally on the alloy sample, ablates the surface and forms the plasma and spectrum signals. With this method, large laser-inducted breakdown spectroscopy (LIBS) signal enhancements, 45-fold most, as well as enhanced signal-to-noise ratio and electronic temperature, are observed comparing to the signal generated by a welding torch only. Also, the results affected by the negative delay time of this pre-ablation short-pulse laser and the geometric position of the detective optical fibers are also discussed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 103003 (2012)
Microstructure of Welding Seam and Fusion Area in the Joint of TiNi/Pure Nickel/Stainless Steel by Laser Welding
Chen Yuhua, Gong Weihuai, Ge Junwei, Yu Liang, Ke Liming, and Liu Fencheng
Pure nickel wire is added into the butt joint of 0.2 mm thick TiNi alloy/stainless steel, and they are welded by pulsed laser. The morphological image and the interface microstructures of the fusion area are investigated. The results show that the characteristics of the welded joint center is extension of the continuouPure nickel wire is added into the butt joint of 0.2 mm thick TiNi alloy/stainless steel, and they are welded by pulsed laser. The morphological image and the interface microstructures of the fusion area are investigated. The results show that the characteristics of the welded joint center is extension of the continuous growth grain. The length of the fern-leaf crystal can reach about 200 μm which may span several fish-scales lines formed by pulsed laser. The morphological image of welded joint with both sides of base material fusion is completely different. In the joint interface of stainless steel base material, the branch crystal grows along fusion line of stainless steel base material, and there have second crystal axis between the branch crystals. In the fusion area between TiNi alloy and welded joint, there is a transition layer between TiNi alloy and welded joint, whose width is about 5 μm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 103004 (2012)
Laser Cleaning of the Contamination on the Surface of Sandstones and Optics
Ye Yayun, Qi Yang, Yuan Xiaodong, Cheng Xiaofeng, Wang Haijun, Luan Xiaoyu, Qin Lang, Wang Hongbin, He Qun, and Ma Zhiqiang
Compared the conventional cleaning methods (chemical cleaning, ultrasonic cleaning), laser cleaning is recognized as a effective cleaning method without damage, precise removal, avoiding environments pollution and it is widely studied and used. According to the different mechanisms, laser cleaning can be classified as Compared the conventional cleaning methods (chemical cleaning, ultrasonic cleaning), laser cleaning is recognized as a effective cleaning method without damage, precise removal, avoiding environments pollution and it is widely studied and used. According to the different mechanisms, laser cleaning can be classified as dry laser cleaning, steam laser cleaning and laser plasma shockwave. In the fields of cultural relics protection, the diseases on the surface of stone relics will affect the conservation and artistic quality of relics. In the high-power laser facility, contaminations on the surface of optics seriously limit normal operation of the facilities. Laser cleaning is used for removal the ink mark contamination on the surface of sandstone and the particles and grease contamination on the surface of gold-coated K9 glass. The laser cleaning effect has been characterized by optical microscopy, dark-field imaging, ultraviolet-visible-near infrared spectroscopy, X-ray photoelectron spectroscopy. The results indicated the cleaning effect is obvious and effective..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 103005 (2012)
Key Factors Selection on SiC Mirror CCOS Polishing
Fan Di
As aerospace technology and laser technology develop rapidly, higher demand for optical system is brought forward. With a number of excellent physical properties, SiC becomes a very promising material for speculums.The mechanism of polishing on SiC mirror is studied. And the key factors affecting the SiC CCOS (computerAs aerospace technology and laser technology develop rapidly, higher demand for optical system is brought forward. With a number of excellent physical properties, SiC becomes a very promising material for speculums.The mechanism of polishing on SiC mirror is studied. And the key factors affecting the SiC CCOS (computer controled optic surface) polishing, such as tools, abrasives, load, speed and slurry pH are studied, chosen and Optimized..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 103006 (2012)
Pulsed Laser Deposition Technology for High Performance Diamond-Like Carbon Films on Infrared Window
Cheng Yong, Wang Shuyun, Guo Yanlong, Huang Guojun, Lu Yimin, Wan Qiang, and Liu Xu
Diamond-like carbon (DLC) film characteries high transmittance in wide spectrum, high hardness, good heat exchange and stability. It can be used as perfect anti-reflective and protective film for infrared windows. However, DLC films in existence can not be used under bad conditions, such as flying in high mach number oDiamond-like carbon (DLC) film characteries high transmittance in wide spectrum, high hardness, good heat exchange and stability. It can be used as perfect anti-reflective and protective film for infrared windows. However, DLC films in existence can not be used under bad conditions, such as flying in high mach number or steering in ocean. Compared to other deposition methods, pulsed laser deposition (PLD) has many merits. Principle and characters of PLD to deposite DLC film were introduced. Problems and key technology for engineering application were also analyzed. DLC films were deposited by PLD. The nano-hardness was up to 44 GPa, inner-stress is only 0.8 GPa and adhesion of critical load is 59.1 mN. Average transmittance of ZnS, Si and Ge windows coated by DLC films and common anti-reflective films reached 82%~91%. Uniform DLC film was deposited on 150 mm substrate and thickness asymmetry no larger than 2%. The windows coated by DLC films passed military standard tests and realized optical engineering application..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 103007 (2012)
Thermodynamic Study on Laser-Induced Plasma in CO2 Laser Welding of Aluminum Alloy
Zhang Shenghai, Shen Yifu, and Zhu Zuojun
The thermodynamics behaviors of laser-induced plasma have been studied during CO2 laser welding on 6061 aluminum alloy with an optical multicultural analyzer and a high-speed camera. The plasma induced by laser in the initial stage and all the welding process have been analyzed in a stable welding process as the same aThe thermodynamics behaviors of laser-induced plasma have been studied during CO2 laser welding on 6061 aluminum alloy with an optical multicultural analyzer and a high-speed camera. The plasma induced by laser in the initial stage and all the welding process have been analyzed in a stable welding process as the same as unstable welding process. The experimental results demonstrate that the deviation between electronic temperature and ionization temperature of plasma is very obvious in the initial stage during laser welding, then tends to balance gradually, in the same time, temperature gradient of plasma become smaller. In the stable welding process, there is only a small influence of laser power increase on temperature of the plasma, but the influence of the plasma′s size on weld area is important. When the plasma temperature increases sharply with the pressure increasing in the keyhole, the plasma will move up and down, it will induce in the interrupt of welding process or produce blowholes. Moreover, the size fluctuation of plasma will worsen weld shaping..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 103008 (2012)
Laser Physics
High Peak-Power Q-Switched All-Fiber Pulsed Laser Based on Acousto-Optic Modulator
Ji Xiang, Zhou Pu, Wang Xiaolin, Su Rongtao, Lu Qisheng, and Zhao Yijun
An all-fiber pulsed laser which can output different characteristic pulse laser by adjusting an acousto-optic modulator (AOM) is introduced. The pulses full width at half maximum (FWHM) vary from 3 ns to 900 ns at the repeat-frequency modulated to 10 kHz. Average output power 1.24 W is obtained at 10 kHz, and FWHM is 6An all-fiber pulsed laser which can output different characteristic pulse laser by adjusting an acousto-optic modulator (AOM) is introduced. The pulses full width at half maximum (FWHM) vary from 3 ns to 900 ns at the repeat-frequency modulated to 10 kHz. Average output power 1.24 W is obtained at 10 kHz, and FWHM is 65 ns, single-pulse power is 0.13 mJ and peak power is 2 kW. At 100 Hz peak-power can reach 10 kW with output power 84 mW, single pulse power 0.84 mJ and FWHM 86 ns. The all-fiber laser has simple configuration, its parameter can be adjusted by AOM easily, which can greatly extend the applications in power amplification, pulse-compression and high-repeat frequency as laser seeds..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 102001 (2012)
1550 nm Tunable External Cavity Semiconductor Laser Based on Single Cavity All-Dielectric Thin-Film Fabry-Perot Filter
Lu Yuanfu, Xiao Xiao, Liu Wenquan, Feng Guangzhi, Gong Xiaojing, Yu Wenlong, Shi Huafeng, Li Jiao, Jin Lei, Jiao Guohua, Lü Jiancheng, and Yu Fengqi
A 1550 nm linearly tunable external cavity semiconductor laser (ECSL) based on single cavity all-dielectric thin-film Fabry-Perot filter is proposed and realized here. Its internal optical components as well as their operation mechanisms are introduced one by one first, and then its longitudinal mode output characterisA 1550 nm linearly tunable external cavity semiconductor laser (ECSL) based on single cavity all-dielectric thin-film Fabry-Perot filter is proposed and realized here. Its internal optical components as well as their operation mechanisms are introduced one by one first, and then its longitudinal mode output characteristic is analyzed theoretically. At last, the experiment platform for the output characteristics measurement of the tunable ECSL is set up; under different experimental conditions and with optical spectrum analyzer, scanning Fabry-Perot interferometer versus laser power meter, accurate and real-time measurements for the output wavelength, output line-width and output power of the tunable ECSL during its tuning process are executed. The optimal experimental condition from the measured datum is summed up, and the tunable ECSL relevant parameters under this condition is obtained. The tunable ECSL will have a linear mode-hop-free wavelength tuning region of 1547.203~1552.426 nm, a stable output optical power in the range of 40~50 μW, and a stable output longitudinal mode distribution of a single longitudinal mode with a line-width in the range of 100~150 MHz. This tunable ECDL could be used in the application of environmental monitoring, atomic and molecular laser spectroscopy research, precise measurements, and so on..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 102002 (2012)
Numerical Simulation of the Gain Characteristics of Optically Pumped Vertical External Cavity Surface Emitting Lasers
Hua Lingling, Yang Yang, Song Yanrong, and Zhang Peng
To investigate the gain characteristics of optically pumped vertical external cavity surface emitting lasers, taking InGaAs/GaAs strained quantum wells as an example, a complete system model which considers all the effects of the band-gap, band-edge discontinuities and band structure is established. In view of the valeTo investigate the gain characteristics of optically pumped vertical external cavity surface emitting lasers, taking InGaAs/GaAs strained quantum wells as an example, a complete system model which considers all the effects of the band-gap, band-edge discontinuities and band structure is established. In view of the valence band mixing and the wave function mixing, the 6×6 effective-mass Luttinger-Kohn Hamiltonian is solved by using the finite difference method, and the conduction-band structures, the valence-band structures and envelope functions are obtained. And then the material gain and spontaneous radiation spectrum with linear Lorentzian function are simulated numerically. Finally, the effects of the well width, carrier density, temperature and other factors on the quantum-well gain are discussed. The calculated results provide a theoretical basis for the optimized design of optically pumped vertical external cavity surface emitting lasers..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 102003 (2012)
Research on Cladding Light Stripping in Double-Cladding All-Fiber Laser
Wang Wenliang, Leng Jinyong, Guo Shaofeng, Cao Jianqiu, and Jiang Zongfu
The output performance and stability of double-cladding all-fiber laser are both affected by the ability of stripping cladding light. The removing pump light will influence the monochromaticity and beam quality of fiber laser, cause damage to the output device and even damage optical device. The common method is recoatThe output performance and stability of double-cladding all-fiber laser are both affected by the ability of stripping cladding light. The removing pump light will influence the monochromaticity and beam quality of fiber laser, cause damage to the output device and even damage optical device. The common method is recoating the double-cladding fiber (DCF) with a high index gel, which strips the cladding light quickly within the first few millimeters and makes the heat locally concentrated. A method using a group of gels to strip the cladding light is adopted. The commercial software Zemax and Matlab are used to simulate the stripping progress of cladding light, and an experimental verification system is presented. The results indicate that the proposed method can strip the cladding light gradually over the length of the fiber with an attenuation ability of 20 dB, and the thermal distribute is uniform without local temperature too high..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 102004 (2012)
High-Gain Sub-Nanosecond Nd:YAG Rod Double Pass Amplifier
Wang Jinguo, Sun Zhe, Jiang Menghua, Hui Yongling, Lei Hong, and Li Qiang
The experiment of sub-nanosecond pulse width Nd:YAG double-pass amplification is studied. Double pass amplifier gain medium is Nd:YAG rod with 3 mm×120 mm size and doping atomic fraction of 1.0%. The two end surfaces of Nd:YAG rod with an angle of 1.5° is designed to avoid self-oscillation and amplified sponThe experiment of sub-nanosecond pulse width Nd:YAG double-pass amplification is studied. Double pass amplifier gain medium is Nd:YAG rod with 3 mm×120 mm size and doping atomic fraction of 1.0%. The two end surfaces of Nd:YAG rod with an angle of 1.5° is designed to avoid self-oscillation and amplified spontaneous emission (ASE) effect. The beam expanding lens magnification is optimized appropriately, the seed laser spot area is selected about 80% of Nd:YAG rod surface area to obtain a higher efficiency. The master oscillator output laser with single pulse energy of 0.16 mJ, repetition frequency of 5 Hz, M2 of 1.5, and pulse width of 0.964 ns is obtained. The Nd:YAG double-pass amplifier output laser with single pulse energy of 88 mJ, M2 of 1.7, stability of ±3%, pulse width of 0.975 ns has been obtained and the total gain is 550..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 102005 (2012)
Influence of the Long Fall Time of KD*P Pockels Cell on Output Characteristics of Solid-State Cavity-Dumped Laser
Wang Xiaofa, Fan Zhongwei, Yu Jin, Shi Zhaohui, Huang Ke, Huang Yutao, and Lian Fuqiang
A low-repetition-rate pulsed LD-pumped cavity-dumped solid-state lasers are designed, in order to minimize the influence of losses, two thin film polarizer are used in the cavity, so that the higher reflectivity of vertical vibration of linearly polarized light is retained in the cavity. Based on this device, The influA low-repetition-rate pulsed LD-pumped cavity-dumped solid-state lasers are designed, in order to minimize the influence of losses, two thin film polarizer are used in the cavity, so that the higher reflectivity of vertical vibration of linearly polarized light is retained in the cavity. Based on this device, The influence of the longer fall time of Pockels cell driving power influence on solid-state cavity-dumped lasers has been studied experimentally. The results show that when the fall time of Pockels cell driving power is longer than a round-trip time in the cavity, some significant changes will occur in the output characteristics of the laser, with the increase of current intensity, the pulse width will increase, and the pulse energy increases first and then decreases; with the increase of the gating time of Pockels cell power, some similar changes will occur on the pulse width and the pulse energy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 102006 (2012)
Three Mode-Locking States in All-Normal-Dispersion Fiber Laser at Low Repetition
Liu Shiyao, Chen Shengping, Song Rui, Liu Tong, and Hou Jing
An all-normal-dispersion ytterbium-doped linear-cavity fiber laser mode-locked by a semiconductor saturable absorber mirror (SESAM) is reported. Without anomalous dispersion part, output pulses are highly-chirped and fundamental repetition rate is 435.6 kHz. Three mode-locking states are observed by adjusting polarizatAn all-normal-dispersion ytterbium-doped linear-cavity fiber laser mode-locked by a semiconductor saturable absorber mirror (SESAM) is reported. Without anomalous dispersion part, output pulses are highly-chirped and fundamental repetition rate is 435.6 kHz. Three mode-locking states are observed by adjusting polarization controller and pump power. Characters of these states, such as spectrum, pulse shape and stability, are analyzed in control experiments..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 102007 (2012)
Polarization Singularities of Radially Polarized Beam Diffracted by a Triangular Multipoint Plate
He Meng, Liu Yongxin, and Pu Jixiong
Based on the Fraunhofer diffraction integral formula, the propagation expressions for radially polarized beam diffracted by a triangular multipoint plate (TMP) are derived. Through the theoretical calculation and experiments, the intensity distribution in the diffraction field arranged periodically is got. The polarizaBased on the Fraunhofer diffraction integral formula, the propagation expressions for radially polarized beam diffracted by a triangular multipoint plate (TMP) are derived. Through the theoretical calculation and experiments, the intensity distribution in the diffraction field arranged periodically is got. The polarization singularities of radially polarized beam in the diffraction field by using the complex Stokes fields is analyzed. It is shown that the light intensity patterns varies with the N-value of the TMP. The number of the polarization singularities increases with the N-value of the TMP. The beam parameters (the wavelength and the waist width of the beam), transmission distance and the parameters of the TMP (the size of each side of the triangle) have influences on the positions of the polarization singularities. The creation and annihilation of the polarization singularities may appear as the N-value of the TMP varies..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 102008 (2012)
Coaxial Degree Characteristics Between the Pumping Light and Laser Resonant Cavity in End-Pumping DPL
Tang Yingde, Guo Zhen, Wang Shiyu, Cai Defang, Wen Jianguo, and Li Bingbin
In laser diode end-pumping solid-state lasers, the departure gene is introduced to describe the coaxial degree betweem the pumping light and the columniform laser crystal. The effects of the departure gene on the gain efficient of the oscillating modes and output beam quality are analyzed in theory, and the correspondiIn laser diode end-pumping solid-state lasers, the departure gene is introduced to describe the coaxial degree betweem the pumping light and the columniform laser crystal. The effects of the departure gene on the gain efficient of the oscillating modes and output beam quality are analyzed in theory, and the corresponding experiment is done with the fiber coupling diode lasers end-pumping Nd:YAG lasers. The results of the theory are in accordance with that of experiment: the departure gene is smaller, the gain of lower order mode becomes higher and the output beam quality changes better. Therefore, in order to obtain the lower order mode output with higher gain and better beam quality, control the coaxial degree between the pumping light and laser crystal is an important measure besides holding proper resonat cavity..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 102009 (2012)
Effects of Temperature Gradient on Transversal Modes in Fiber Lasers
Ren Yajie, Cao Jianqiu, Leng Jinyong, and Guo Shaofeng
The impact of thermal induced temperature gradient on the properties of transversal modes propagating in fiber lasers is carefully investigated. The thermal distribution in the cross section of fiber laser is figured out through a predigested heat conductive model, and then, the properties of transversal modes are analThe impact of thermal induced temperature gradient on the properties of transversal modes propagating in fiber lasers is carefully investigated. The thermal distribution in the cross section of fiber laser is figured out through a predigested heat conductive model, and then, the properties of transversal modes are analyzed by using multiphysics software under different operating conditions or parameters of fiber. It is found that all the transversal modes have a trend of constriction to the core of fiber with rising power level, and this discovery may give one of the explanations how the high order modes appear in single mode high power fiber lasers. As well, when the absorption coefficient or the refractive index-temperature coefficient is growing, the transversal modes also present a constriction trend..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 102010 (2012)
Self-Generated Magnetic Field and Hot Electron Energy Transport in the Interaction of Ultraintense Laser Pulse with Plasmas
A. Abudurexiti, and P. Mejid
Stimulated hot electron and its energy transport mechanism by a linearly-polarized laser interacting with a plasma are studied by using electromagnetic relativistic particle-in cell program simulation. The onset and nonlinear saturation process of electromagnetic instability are discussed. The state of transport of eneStimulated hot electron and its energy transport mechanism by a linearly-polarized laser interacting with a plasma are studied by using electromagnetic relativistic particle-in cell program simulation. The onset and nonlinear saturation process of electromagnetic instability are discussed. The state of transport of energy which is in the heat exchange with electron by the Spitzer-Harm theory is analyzed, electron′s vertical pyrogenation phenomenon that resulted from anisotropic heating of laser is observed. The result of this research indicates that the strong magnetic field excited by instability makes the electron beam deposit the energy within very short distance, meanwhile, restrain the electron therymal current to form when the laser ponderomotive force burst through the electron..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 102011 (2012)
Optical Torques upon a Micro Object Illuminated by a Vortex Beam
Li Donghua, Pu Jixiong, and Wang Xiqing
The torque on a specially shaped micro object produced by a vortex beam is studied based on a ray-optic (RO) model. Based on conservation of momentum and orbital angular momentum, the formulas for the torque along x, y and z directions are derived. The numerical calculation is given to show the dependence of the opticaThe torque on a specially shaped micro object produced by a vortex beam is studied based on a ray-optic (RO) model. Based on conservation of momentum and orbital angular momentum, the formulas for the torque along x, y and z directions are derived. The numerical calculation is given to show the dependence of the optical torques on the inclination angle of the micro object. It is shown that the torque is dependent upon both the light momentum and orbital angular momentum (OAM) of the incident vortex beam. We can control the rotation of the micro object by modulating the topological charge of the incident light beam. Moreover we can make the micro object stop..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 102012 (2012)
Propagation Properties of Partially Coherent Modulated Electromagnetic Square Flat-Topped Pulsed Beams in Free Space
Tao Hua, Zhang Guowen, and Pu Jixiong
Based on the generalized Huygens-Fresnel diffraction integral and the unified theory of coherence and polarization, propagation properties of partially coherent electromagnetic square flat-topped pulsed beams with amplitude and phase modulations in free space are analyzed. The analytical expressions for the cross-spectBased on the generalized Huygens-Fresnel diffraction integral and the unified theory of coherence and polarization, propagation properties of partially coherent electromagnetic square flat-topped pulsed beams with amplitude and phase modulations in free space are analyzed. The analytical expressions for the cross-spectral density matrix of partially coherent electromagnetic square flat-topped pulsed beams with amplitude and phase modulations in free space are derived, and the numerical calculations are also given. It is shown that the spectral intensity distribution of partially coherent electromagnetic square flat-topped pulsed beams is influenced by size of the modulation zone, the depth of amplitude and phase modulations, the coherence length and temporal coherence length of the beams, and transmission distance..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 102013 (2012)
Reduced-Scale Experimental Study on Beam Uplink Propagation in a Relay Mirror System with Vortex Source and Phase Optimization
Wu Huiyun, Ma Haotong, Zhao Haichuan, Xu Xiaojun, Chen Jinbao, Zhao Yijun, Xiong Chengping, and Chen Jun
The relay mirror technology is an important system combat concept under extensive research. Beam blocked and truncated by the receiving Cassegrain telescope causes serious power losses in beam uplink propagation in the relay mirror system, which degrades performance of the relay mirror system. Using vortex beam source The relay mirror technology is an important system combat concept under extensive research. Beam blocked and truncated by the receiving Cassegrain telescope causes serious power losses in beam uplink propagation in the relay mirror system, which degrades performance of the relay mirror system. Using vortex beam source and phase optimization is an effective way to improve power efficiency of beam uplink propagation in the relay mirror system. A reduced-scale experimental installation is established with the same Fresnel number as beam uplink propagation process in the relay mirror system with the following parameters as “1.2 m source aperture, 30 km uplink propagation distance, receiving telescope with 1.2 m outer aperture and 0.24 m inner aperture”. Vortex source is generated by using the NdYVO4 laser and a liquid crystal spatial light modulator with spiral phase distribution, and phase distribution of the vortex source is optimized by using the stochastic parallel gradient descent algorithm. Reduced-scale experimental study on beam uplink propagation in a relay mirror system with vortex source and phase optimization is performed. Results show that power efficiency of beam uplink propagation in the relay mirror system is improved from 71.89% to 91.59% by using vortex source and phase optimization..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 102014 (2012)
Research of Micro Laser Thruster Engine Performance Based on Thermodynamic Cycle Analysis
Ye Jifei, Hong Yanji, Wang Guangyu, and Wang Diankai
In the recent years, the micro laser thruster is the focus of the applied research of laser propulsion technology, which is aimed to apply in the task of pose and orbit control of the micro satellite. Based on the thermodynamic cycle analysis of the micro laser thruster engine, the effect factor on thermodynamic cycle In the recent years, the micro laser thruster is the focus of the applied research of laser propulsion technology, which is aimed to apply in the task of pose and orbit control of the micro satellite. Based on the thermodynamic cycle analysis of the micro laser thruster engine, the effect factor on thermodynamic cycle efficiency is researched. The method of improving the propulsion performance is proposed, which is realized by changing the laser power density and target doping content. The regularity of the engine performance is verified by the experiment. The results indicate that the thermodynamic cycle efficiency is influenced by both laser and target, the pressure behind the shock wave could be increased by the increasing of laser power density, the specific impulse could be increased and the impulse coupling coefficient could be decreased; laser energy absorption could be intensified by the doped target, both specific impulse and impulse coupling coefficient are increased, and the thermodynamic cycle efficiency could be increased to some extent by the increasing of laser power density and target doping content..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 102015 (2012)
Materials and Thin Films
Variation of Absorptivity with Time of Azo-Material in Absorbption Modulation Micro-Fabrication Technique
Li Da, Wang Shu, Zhao Xing, Fang Zhiliang, and Yuan Xiaocong
The super-resolution micro-fabrication technique based on the optical absorption modulation of azo-material is attracting attentions for decades. To reveal the mechanism of the optical absorbance modulation of azo-material, the simulations of the variation of absorptivity with time are implemented based on the optical The super-resolution micro-fabrication technique based on the optical absorption modulation of azo-material is attracting attentions for decades. To reveal the mechanism of the optical absorbance modulation of azo-material, the simulations of the variation of absorptivity with time are implemented based on the optical absorption model and the photo-isomerization principles of azo-material. Some membrane samples with different thicknesses are obtained by using a typical azobenzene dye [disperse yellow 7 (DY7)], and the experiment to study the variation of absorptivity with time of these samples is implemented, with 365 nm illumination only and 365 nm and 532 nm illumination together, respectively. The results indicate that the obsorptivity of azobenzene at 365 nm varies significantly due to the photo-isomerization of azobenzene, and it is influnced by the thermal effect due to 532 nm illumination..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 106001 (2012)
Fabrication and Deagglomeration of YAG Nanopowders
Chen Zhongwen, Yang Fu, Chen Jing, Zhou Zhipeng, and Gao Xian′e
Yttrium aluminum garnet (YAG) transparent ceramic has been proved to be one of the best solid-state laser materials in the history of quantum electronics. Its indisputable dominance in solid-state laser application is determined by its unrivalled optical, mechanical and thermal properties. During the fabrication of YAGYttrium aluminum garnet (YAG) transparent ceramic has been proved to be one of the best solid-state laser materials in the history of quantum electronics. Its indisputable dominance in solid-state laser application is determined by its unrivalled optical, mechanical and thermal properties. During the fabrication of YAG transparent ceramic, agglomeration of YAG nanopowders can deteriorate the performance of transparent ceramic. YAG nanopowders are prepared by co-precipitation, then deagglomerated by ball milling and adding Dolapix CE-64. YAG nanopowders and its slurry are characterized by X-ray diffraction (XRD), Zeta potential, laser granulometer and scanning electron microscope (SEM). The results show that YAG nanopowders are well deagglomerated by adding 10 percent of Dolapix CE-64 and ball milling of 24 h..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 106002 (2012)
Fabrication of nano-scale metallic photonic crystals using interference ablation
Zhaoguang Pang, Xinping Zhang, Hongmei Liu, and and Tianrui Zhai
We demonstrate the fabrication and characterization of large area metallic photonic crystals (MPCs) in the form of gold nano-island grating structures. The spectroscopic properties of the MPCs characterized by the angle-resolved optical extinction spectrum measurements show strong couplings between the waveguide resonaWe demonstrate the fabrication and characterization of large area metallic photonic crystals (MPCs) in the form of gold nano-island grating structures. The spectroscopic properties of the MPCs characterized by the angle-resolved optical extinction spectrum measurements show strong couplings between the waveguide resonance modes and the particle plasmon resonance of the gold nanostructures， indicating the success of this fabrication method. The excellent optical responses of the nano-island MPCs with the advantages of large-area fabrication, low cost, and high speed make it show potential applications in optoelectronic devices and sensors..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 106003 (2012)
Modulation Instability in Saturable Nonlinear Negatve-Index Materials with Higher-Order Dispersion
Zhong Xianqiong, Xiang Anping, Cheng Ke, and Cai Qing
The dispersion relation and gain spectra of modulation instability (MI) are analytically deduced in negative-index materials by directly starting from the extended nonlinear propagation equation including saturable nonlinearity and higher-order dispersion and by adopting the linear stability analysis and Drode electromThe dispersion relation and gain spectra of modulation instability (MI) are analytically deduced in negative-index materials by directly starting from the extended nonlinear propagation equation including saturable nonlinearity and higher-order dispersion and by adopting the linear stability analysis and Drode electromagnetic model. And the variations of the equation coefficients with the normalized angular frequencies are calculated in real units for future experimental demonstrations. Then the variations of the gain spectra with the normalized angular frequencies and normalized optical intensities are also calculated and discussed in real units. The results show that, when the normalized angular frequencies are fixed, with the increasing normalized optical intensities, the cut-off frequencies and peak gains of MI will increase before decrease. And the cut-off frequencies and peak gains are different for different normalized angular frequencies. Moreover, the gain spectra will depart far away from the zero point when the normalized angular frequencies are close to the forbidden band region. When the normalized optical intensities are fixed, the cut-off frequencies and peak gains increase with the normalized angular frequencies. And when the normalized angular frequency increases to be close to the forbidden band region, the gain spectrum will shift far away from the zero point..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 106004 (2012)
Third Harmonic Generation with Large-Scale Rapid Growth KDP Crystals
Wang Fang, Zhou Lidan, Han Wei, Li Keyu, Wang Liquan, Feng Bin, Jia Huaiting, Xiang Yong, Su Jingqin, and Jing Feng
The frequency conversion performance of a large scale rapid growth KDP crystal is studied. Using the orthogonal polarization interferometry (OPI) technique, the spatial refractive-index non-uniformities which prohibit the attainment of phase matching at all locations in the crystal is measured. Then third harmonic geneThe frequency conversion performance of a large scale rapid growth KDP crystal is studied. Using the orthogonal polarization interferometry (OPI) technique, the spatial refractive-index non-uniformities which prohibit the attainment of phase matching at all locations in the crystal is measured. Then third harmonic generation (THG) experiments with the large scale rapid growth KDP doubler on the prototype of SG-III laser facility to estimate the influence of refractive-index non-uniformities on conversion efficiency and 3ω beam near-field are conducted. According to the experimental results, this large scale rapid growth KDP crystal meets the basic requirements. But for specific applications, other aspects such as the stimulated Raman scattering gain coefficient and laser-induced damage threshold should be further considered..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 106005 (2012)
Scattering Properties of Polymer Dispersed Liquid Crystal with Different Angles and Voltages
Zhao Yun, Zhang Bin, Wang Fen, Pan Xuefeng, Tao Weidong, and Dong Jianfeng
The scattering property of polymer dispersed liquid crystal (PDLC) film is tested at different angles and voltages. The film is prepared via polymerition induced phase seperation method. At the 10V voltage, scattering intensity attains to the minimum when the angle is less than 26°. In contrast, the maximum appearThe scattering property of polymer dispersed liquid crystal (PDLC) film is tested at different angles and voltages. The film is prepared via polymerition induced phase seperation method. At the 10V voltage, scattering intensity attains to the minimum when the angle is less than 26°. In contrast, the maximum appears when the angle degree exceeds 26°. In addition, the data depending on changes of applied electric field reveals a significant difference of scattering spectra in different angles. Blue light intensity increases at higher level of external voltage between 0°~5°. Ranging from 6°~25°, the intensity of scattered light increases with voltage at first and then decreases. And the magnitude of voltage in the big wave peak increases when angle degree decreases. When the scattering angle is greater than 26°, the intensity of blue light decreases with the increase of voltage. Single scattering theory is adopted to discuss and analyze the phenomenon..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 107001 (2012)
Effect of Glass Substrate and Surface Roughness on Ellipsometric Measurement of Silicon Nitride Films
Liu Wende, Chen Chi, Zhang Hang, Guo Wei, Yu Jing, Fan Qiming, and Xu Yingying
In spectroscopic ellipsometric measurement, the backside reflection of the glass substrate has great influence on the tested results. Ellipsometric measurement and model calculation are carried out for the silicon nitride film deposited on glass substrate of flat panel displays. The coherent model of the baskside refleIn spectroscopic ellipsometric measurement, the backside reflection of the glass substrate has great influence on the tested results. Ellipsometric measurement and model calculation are carried out for the silicon nitride film deposited on glass substrate of flat panel displays. The coherent model of the baskside reflection, i.e. "air-substrate-air" is used to calculate and obtain the refractive index of the glass substrate which agrees well with the data provided by manufacturer. Tauc Lorentz model is used in data analysis for the silicon nitride film to discuss the effect of the interface layer between the film and substrate, the surface roughness on the optical constants and model fitting. The results suggest that the inclusion of the interface is necessary for improving the degree of fitting in the case of lattice mismatch between the film and substrate. The optical constants and film structure of the film system are presented..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 107002 (2012)
Measurement and Metrology
Measure Truck Carriage Volume with Laser Pulse Time-of Flight
Xing Jichuan, and Tong Mingming
Truck carriage volume is measured with laser pulse time-of-flight range finding. By this scheme, the carriage part can be correctly segmented from the whole truck with 2~6 axles and calculated. With the third height moment, which is based on the gray moment for edge detection algorithm in digital image processing, the Truck carriage volume is measured with laser pulse time-of-flight range finding. By this scheme, the carriage part can be correctly segmented from the whole truck with 2~6 axles and calculated. With the third height moment, which is based on the gray moment for edge detection algorithm in digital image processing, the head and underframe of trucks with all kinds of axles are divided and computed for the volume of the carriage. Especially for 6-axle truck with the bench-shape, the point of bench turn and volume of the carriage are accurately calculated. Besides, using the technique of rolling-over and merging of the cross section data of truck body, the number of laser scanner is downsized to 2. The above techniques are already utilized in the project for carriage volume measurement. With a lot of results proved, carriage volume of trucks can be rightly calculated..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 108001 (2012)
Subaperture stitching testing of an aspherical surface
Xiaokun Wang
For the purpose to test large and off-axis aspheric surfaces without the aid of other null optics, a novel method combined subaperture stitching and interferometry is introduced. The basic principle and theory of the technique are researched, the synthetical optimization stitching mode and effective stitching algorithmFor the purpose to test large and off-axis aspheric surfaces without the aid of other null optics, a novel method combined subaperture stitching and interferometry is introduced. The basic principle and theory of the technique are researched, the synthetical optimization stitching mode and effective stitching algorithm are established based on homogeneous coordinates transformation and simultaneous least-squares fitting. The software of SSI is devised, and the prototype for testing of large aspheres by SSI is designed and developed. The experiment is carried on with three subapertures for an off-axis sic aspheric mirror with a clear aperture of 230×141 (mm). For the compare and validation, the asphere is also tested by null compensation, the synthesized surface map is consistent to the entire surface map from the null test, the differences of PV and RMS error are 0.023λ and 0.014λ, respectively; and the relative errors of PV and RMS are 0.57% and 2.74%, respectively .The results conclude that this technique is feasible and accurate. It enables the non-null testing of parts with greater asphericity and larger aperture..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 108002 (2012)
Application of Virtual Grating Phase-Shifting Fringe Method for Three-Dimensional Shape Measurement
Zhu Ronggang, Zhu Rihong, and Li Jianxin
It′s easier to understand in principle and faster to calculate in reconstruction by using the method of phase stepping profilometry (PSP) for three-dimensional (3-D) shape measurement. But it needs three images at least and can′t produce the absolute value of phase stepping to avoid error in practice. Virtual grating pIt′s easier to understand in principle and faster to calculate in reconstruction by using the method of phase stepping profilometry (PSP) for three-dimensional (3-D) shape measurement. But it needs three images at least and can′t produce the absolute value of phase stepping to avoid error in practice. Virtual grating phase-shifting is proposed and it just needs one image. We first calculate or detect the base frequency f0, then use the computer to built two images by expression of cos(2πf0x) and sin(2πf0x) with π/2 phase difference. Multiply the images with original image separately, we filter the images with low pass filter and reconstruct the 3-D profile of original object by using PSP algorithm. This method reserves the advantage of PSP, solves the shortcoming of and cannot set absolute value of the phase step. In addition, the low pass filter can filter the nose of high frequency by itself, which can be used for measuring 3-D profile with non-sharp surface especially..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 108003 (2012)
Ship-Borne Attitude Positioning System Based on Laser Gyro Platform
Long Dafeng, Zhang Xiaoming, Sun Junli, and Liu Jun
To ensure that the shipboard satellite receiver get enough of their own real-time, accurate attitude information, considering the requirements low-cost, this paper introduced micro-electro-mechanical system (MEMS) inertial device to design attitude positioning system for satellite receiver. The high precision laser gyrTo ensure that the shipboard satellite receiver get enough of their own real-time, accurate attitude information, considering the requirements low-cost, this paper introduced micro-electro-mechanical system (MEMS) inertial device to design attitude positioning system for satellite receiver. The high precision laser gyro navigation system in the bow is used to combine MEMS inertial navigation system (INS) in the stern. The errors of the MEMS strapdown inertial navigation system are analyzed and the dynamic model of the integrated navigation system was established. In order to solve the low accuracy problem of MEMS INS attitude Sage-Husa adaptive filter is utilized to estimate inertial navigation system error, and correct the attitude calculation results of the MEMS INS. The experimental verification is feasible..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 108004 (2012)
Study on Magnetostrictive Coefficient Based on Multi-Beam Laser Heterodyne
Li Yanchao, Wang Chunhui, and Qu Yang
A method of multi-beam laser heterodyne measurement for magnetostrictive coefficient is proposed. Based on Doppler effect and heterodyne technology, loading the information of parameter under test to the frequency difference of the multi-beam laser heterodyne signal by the frequency modulation of the oscillating mirrorA method of multi-beam laser heterodyne measurement for magnetostrictive coefficient is proposed. Based on Doppler effect and heterodyne technology, loading the information of parameter under test to the frequency difference of the multi-beam laser heterodyne signal by the frequency modulation of the oscillating mirror, this method can obtain many values of parameter after the multi-beam laser heterodyne signal demodulation simultaneously. Processing these values by weighted-average, it can improve the accuracy of the parameter. The magnetostrictive coefficient of the sample under different carrents is simulated by Matlab. The obtained result shows that the relative error of this method is just 0.48%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 108005 (2012)
Novel Method for Structured Light Plane Calibration in Three-Dimensional Vision Measurement
Yu Qian, Zhang Xuping, Zhang Yixin, Wang Shun, and Qi Li
The calibration of structured light plane is the key technique in structured light three-dimensional vision measurement. The traditional methods require expensive equipments and complex procedure, and the efficiency is quite low. A novel method for structured light plane calibration is presented. In this method, a simpThe calibration of structured light plane is the key technique in structured light three-dimensional vision measurement. The traditional methods require expensive equipments and complex procedure, and the efficiency is quite low. A novel method for structured light plane calibration is presented. In this method, a simple two-dimensional planar target is used. The target can be freely moved to different positions in the visible space of the camera if only the target and the structured light plane can intersect to each other. The corresponding world coordinate is set for each target in different positions. Transformation relation among the world coordinate, camera coordinate and image coordinate can be calculated. Through processing, the intersecting lines′ equations of different positions are unified at the camera coordinate system. Then we can use least square method to fit the structured light plane′s equation. The experimental results show that the proposed method is a universal method with high efficiency and simple procedure..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 108006 (2012)
Multi-Spectral Measurement of Basic Oxyogen Furnace Flame Temperature Using Wavelet-Networks
Wang Yongqing, Chen Yanru, Shao Yanming, Chen Jingjing, and Chen Feinan
Distribution of basic oxygen furnace (BOF) flame is an important basis for determining the content of molten steel temperature and composition. Analyzing 350~1100 nm spectral data from the furnace mouth, furnace flame atomic emission spectra overlap in a continuous or "black body" radiation, which are in a clDistribution of basic oxygen furnace (BOF) flame is an important basis for determining the content of molten steel temperature and composition. Analyzing 350~1100 nm spectral data from the furnace mouth, furnace flame atomic emission spectra overlap in a continuous or "black body" radiation, which are in a clear visible radiation. Data collected from nanjing iron and steel company′s steel-making furnace as sample data are used to implement the algorithms. The sample contains 400 data pairs. A model is applied based on the theory of wavelet analysis and neural networks to predict the temperature of the furnace flame and the results are analyzed in detail. It is shown that the method of neural networks with compact structure can give better hit rates of prediction; the temperature predicted by the model is inosculated to the temperature obtained by converter sub-lance comparatively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 108007 (2012)
Data Processing of Photonic Doppler Velocimetry System
Wang Jian, Xiang Hongliang, Bi Chonglian, and Wu Chongqing
Photonic Doppler velocimetry (PDV) is a new type of laser velocimetry system. It is widely used in the velocity measurement of the shock wave, detonation wave and other short-time high-velocity movement. Data processing is an important part of it, which purpose is to obtain the velocity information of the moving targetPhotonic Doppler velocimetry (PDV) is a new type of laser velocimetry system. It is widely used in the velocity measurement of the shock wave, detonation wave and other short-time high-velocity movement. Data processing is an important part of it, which purpose is to obtain the velocity information of the moving target from the measurement data mixed with a lot of noise. Based on the PDV principle, target PDV data, obtained from laser shock peening experiment, are processed using the fringe method, short time Fourier transform(STFT) and continuous wavelet transform (CWT). Some unique methods are proposed to eliminate noise, singularities and choose the optimal wavelet. At the same time, the errors, real-timing and validity of the three methods are compared..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 108008 (2012)
Electrical Calibration of High Intensity Laser Energy′s Measuring
Tang Ling, Wang Chao, Liu Hua, Chen Ji, Dang Zhao, Peng Zhitao, Hu Dongxia, Dai Wanjun, and Li Xiaoqun
As the development of inertial confinement fusion (ICF) driver, the aperture of laser beam increases gradually, and the energy need to be measured precisely. However, the present calibration method doesn′t satisfy the measuring precision degree (with uncertainty not greater than 2%). A new electrical calibration methodAs the development of inertial confinement fusion (ICF) driver, the aperture of laser beam increases gradually, and the energy need to be measured precisely. However, the present calibration method doesn′t satisfy the measuring precision degree (with uncertainty not greater than 2%). A new electrical calibration method of high intensity laser calorimeters is presented. Semiconductors consisting of Bi2Te3-Sb2Te3 are used as energy converting devices. Research on calorimeters′ calibration which uses electrical energy to substitute the laser energy has been done. Thermal model of volume-absorbing glass under pulsed-laser heating and electrical heating has been developed. Results show that, electrical heating and laser heating are equivalent in ambient thermodynamics models. Some experimental results have been obtained, which demonstrate the feasibility of the electrical heating′s application..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 108009 (2012)
Measurement of Phase Modulation Characteristics of Liquid Crystal Optical Phased Arrays
Wang Xiaozhang, Li Qi, and Wang Qi
In order to measure the phase modulation characteristics of the liquid crystal optical phased array with 633 nm, the whose design wavelength is 1550 nm, the Tymann Green interferometry combined with the polarized light interference methods are used. The experimental results show that the phase delay of the liquid crystIn order to measure the phase modulation characteristics of the liquid crystal optical phased array with 633 nm, the whose design wavelength is 1550 nm, the Tymann Green interferometry combined with the polarized light interference methods are used. The experimental results show that the phase delay of the liquid crystal optical phased array is a linear distribution. In 0~255 gray-scale range for 633 nm, the actual phase modulation is 0~3.76π. The phase modulation characteristics have a good linearity in 135~255 gray-scale range. It can be used as the liquid crystal work area. Since the accuracy and precision of the liquid crystal phase control are depend the loading gray scale to achieve, so measuring the relation between the phase delay and gray has an important value in high precision light beam deflection and tracking for liquid crystal optical phased array..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 108010 (2012)
Wave Aberration Measuring System of Optical Lens with Small-Field of View Based on Auto-Collimating Principle
Zhang Xuemin, Wei Ruyi, Li Hua, Duan Jiayou, and Yang Jianfeng
In order to measure the wave aberration of optical lens with small field of view rapidly and precisely, a new wave aberration measuring system based on both auto-collimation principle and Fizeau spherical laser interferometer measurement principle is described. The wave aberration measurement principle by Fizeau spheriIn order to measure the wave aberration of optical lens with small field of view rapidly and precisely, a new wave aberration measuring system based on both auto-collimation principle and Fizeau spherical laser interferometer measurement principle is described. The wave aberration measurement principle by Fizeau spherical laser interferometer is introduced. The assembling and measuring methods of this new auto-collimation-based wave aberration system are discussed and analyzed in detail. By using the characteristic of auto-collimation optics, the in-terferometer′s axis, the optical lens′s optical axis and the high-precision reflector′s axis are precisely determined, and the fast assembly of the optical system is implemented too. Analyses reveal that this system can be an effective solution to the optical axis deviation problem in measuring the wave aberration of optical lens with small-field of view, and implementing the wave aberration test of optical lens rapidly and accurately..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 108011 (2012)
Micro-Vibration Interferometry Based on Nonlinear Crystal of GaAs
Gao Xiaojing, Zhang Bin, Yan Bin, and Feng Qibo
Homodyne interferometry based on nonlinear GaAs crystal for micro-vibration measurement is investigated by conducting an experiment. In the interferometer that with 532 nm laser, signal beam is modulated by a vibrating mirror and interfers with reference beam on the surface of GaAs crystal. The interferometric signal pHomodyne interferometry based on nonlinear GaAs crystal for micro-vibration measurement is investigated by conducting an experiment. In the interferometer that with 532 nm laser, signal beam is modulated by a vibrating mirror and interfers with reference beam on the surface of GaAs crystal. The interferometric signal produces photo-induced current that relates to vibration amplitude when vibration frequency is beyond cut-off frequency of GaAs crystal. Influences of spatial frequency of interferometric fringes and electrode space of GaAs crystal on the photo-induced current of the GaAs crystal are studied and the optimum parameters are obtained. Experimental results are compared with those from a commercial vibration measurement instrument and coincided well..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 108012 (2012)
Research on the Long Range Precision Alignment System with Sub-Micron Accuracy
Zhang Jinlong, Lian Meilin, Xu Hui, and Lei Huahuan
In view of the features of panel position of shadow-mask plasma display pare (SMPDP), two methods of precision positioning are brought forward: image positioning method and grating positioning method. The compound control system for precision positioning is set up using two kinds of the positioning technique, in which In view of the features of panel position of shadow-mask plasma display pare (SMPDP), two methods of precision positioning are brought forward: image positioning method and grating positioning method. The compound control system for precision positioning is set up using two kinds of the positioning technique, in which the image positioning method is used as the coarse alignment and the grating positioning method is used as the fine alignment. By using the two-step alignment, the high alignment accuracy and quick alignment speed are obtained in the big long positioning range. The algorithms such as fast image edge detection, character extraction, precision gratings detection and precise driving strategy are adopted to effectively improve positioning accuracy and reliability of the device. The experimental result shows the two-step alignment can perform positioning accuracy of ±0.15 μm in the working range of 50 mm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 108013 (2012)
Optical Communication
Gain Spectrum Characteristic under Raman Scattering and Parametric Amplification in Dispersion Shifted Fiber
Jia Weiguo, and Qiao Lirong
The coherently coupled nonlinear Schrdinger (NLS) equation in which Parametric Amplification and Raman scattering together acting has been utilized in high birefringence Dispersion Shifted fiber. The gain spectrums have been studied under Raman scattering and parametric amplification together acting when the pump waveThe coherently coupled nonlinear Schrdinger (NLS) equation in which Parametric Amplification and Raman scattering together acting has been utilized in high birefringence Dispersion Shifted fiber. The gain spectrums have been studied under Raman scattering and parametric amplification together acting when the pump wave polarization is oriented at 45° between the axes by quoting Lorentzian model of Raman gain spectra in high birefringence Dispersion Shifted fiber. The result shows that the gain spectrums only has relationship with magnitude of third-order dispersion and fourth-order dispersion. The Stokes Gain has displayed single pulse when biggish input power in the normal dispersion regime. So that the T frequency single pulses can been extracted when high birefringence Dispersion Shifted fiber has been used..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 105001 (2012)
Comparison Study on π Phase-Shifted FBG′s Fabrication Methods
Song Zhiqiang, Qi Haifeng, Ni Jiasheng, Zhang Xiaolei, Wang Chang, and Peng Gangding
The two most commonly used fabrication methods of phase-shifted fiber Bragg grating, namely the stepped exposure method (or shielded method) and the phase mask moving method are described. Physical mechanisms of the two methods to introduce phase shift are comparatively analyzed. Using the theoretical model of transferThe two most commonly used fabrication methods of phase-shifted fiber Bragg grating, namely the stepped exposure method (or shielded method) and the phase mask moving method are described. Physical mechanisms of the two methods to introduce phase shift are comparatively analyzed. Using the theoretical model of transfer matrix method numerical simulation of the transmission spectra of phase shift fiber Bragg grating is done, and cross-reference experiments are carried out. The results show that the phase shift of the grating is related to the non-exposed segments of length and core refractive index modulation amount and it′s hard to accurately control in stepped method. While the phase shift is controlled in an amount of 0~2π range and easier to achieve π phase shift grating production in phase mask moving method using Piezo nano-positioning system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 105002 (2012)
Study of Polymer Optical Waveguide Amplifier at 1.55 μm Wavelength
Zheng Libing, Wang Jianbin, Liang Xu, Zhang Yiliang, and Zhang Dan
Er-Yb co-doped polymer waveguide active material is prepared. The three β-diketonate complexes of erbium and ytterbium ［Er1/2Yb1/2(HFA)3(TPPO)2］ is synthesized and doped in PMMA. At the 980 nm pumping light excitation, the full width at half maximum of the complexes′ fluorescence in the 1535 nm is 80 nm. The absorptionEr-Yb co-doped polymer waveguide active material is prepared. The three β-diketonate complexes of erbium and ytterbium ［Er1/2Yb1/2(HFA)3(TPPO)2］ is synthesized and doped in PMMA. At the 980 nm pumping light excitation, the full width at half maximum of the complexes′ fluorescence in the 1535 nm is 80 nm. The absorption and photoluminescence spectra of the active material are observed. Fundamental rate equations and power propagation equations used to simulate the gain factors of the active material excited at pumping light wavelength 980 nm. The influence on the performance of Er-Yb co-doped polymer waveguide amplifier with Er3+ concentration, overlapping factor of the signal laser and pumping laser, and signal emission cross-sections is theoretically calculated. The result of the calculations indicates that when the concentration of Er3+ is 0.3×1020 cm-3 in the active material, the calculated gain is 1.87 dB on a 2cm long waveguide..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 105003 (2012)
Influence of Grating Parameters on Polarization Properties of Linearly Chirped Fiber Bragg Gratings
Guo Bingxia, and Li Qianghua
The wavelength dependency of polarization dependent loss (PDL) in reflection in linearly chirped fiber Bragg gratings (CFBGs) written in single mode fibers is studied. Using the coupled theory and transfer matrix, the evolution with wavelength of PDL as a function of the grating parameters and the birefringence value iThe wavelength dependency of polarization dependent loss (PDL) in reflection in linearly chirped fiber Bragg gratings (CFBGs) written in single mode fibers is studied. Using the coupled theory and transfer matrix, the evolution with wavelength of PDL as a function of the grating parameters and the birefringence value is analyzed. And simulation results show that the chirped grating polarization dependent loss is very significant as the birefringence changes, especially with steep sides. The chirp grating PDL is also affected by the chirp grating coefficient and the modulation depth, which indicates that the linear chirped grating polarization dependent loss is not only dependent on the grating birefringence, but also dependent on other parameters of the chirp coefficient and other parameters. Theoretical analysis and experimental results are matchable to each other..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 105004 (2012)
High sensitivity fiber-optic pressure sensor based on equilibrium structure
Wenhua Wang, and Xinsheng Jiang
A novel high sensitivity diaphragm-based extrinsic Fabry-Pérot (FP) interferometric fiber-optic pressure sensor with back-pressure equilibrium structure is present. The sensor possesses backpressure-independence and small temperature-dependence. The ultra-thin fused silica is bonded to the end surface of the doublA novel high sensitivity diaphragm-based extrinsic Fabry-Pérot (FP) interferometric fiber-optic pressure sensor with back-pressure equilibrium structure is present. The sensor possesses backpressure-independence and small temperature-dependence. The ultra-thin fused silica is bonded to the end surface of the double holes fused silica ferrule by use of CO2 laser, and the double holes structure enhances the sensor performance. The operating point does not drift. The sensor with sensitivity of 9.51 nm/kPa (65.57 nm/psi) has been achieved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 105005 (2012)
Performance Analysis of Optical Wireless Communication Based on LDPC Codes and MIMO
Hao Shiqi, and Leng Jiaofeng
Atmospheric turbulence produces fluctuations in the irradiance of the transmitted optical beam, severely degrading the performance over optical wireless links. Performance of optical wireless communication based on low-density parity-check (LDPC) codes and multiple-input multiple-output (MIMO) is investigated. DecodingAtmospheric turbulence produces fluctuations in the irradiance of the transmitted optical beam, severely degrading the performance over optical wireless links. Performance of optical wireless communication based on low-density parity-check (LDPC) codes and multiple-input multiple-output (MIMO) is investigated. Decoding algorithm of repetition coded MIMO (rep MIMO) and space-time coded MIMO (ST MIMO) based on LDPC codes is investigated, finally it is simulated in the atmospheric turbulence channel. Simulation results show that rep MIMO outperforms ST MIMO, and LDPC codes have excellent error correction capabilities and access to a larger coding gain. Therefore the sheme based on LDPC codes and rep MIMO can mitigate fading effectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 105006 (2012)
Research on Influence of Atmospheric Turbulence for Laser Communication at High Data Rate by Simulation Experiments
Fu Qiang, Jiang Huilin, Zeng Zongyong, Wan Xiaoman, and Liu Zhi
Research methods, the present situation and the necessity for the influence of high data rate laser communication in atmospheric turbulence are analyzed, a simulation device of high data rate laser communication in atmospheric turbulence is established, the simulation experiments programme for the impact of laser commuResearch methods, the present situation and the necessity for the influence of high data rate laser communication in atmospheric turbulence are analyzed, a simulation device of high data rate laser communication in atmospheric turbulence is established, the simulation experiments programme for the impact of laser communication in the atmospheric turbulence, tested scintillation and the arrival angle fluctuation are put forward. The results show that the atmosphere turbulence simulator irradiance scintillation, the arrival angle fluctuation theory consistent with the -5/3, Scintillation and the arrival angle fluctuation are the main factor to the performance of laser communication. Provided the effective means and method for the further studying effect of high data rate laser communication in the atmospheric turbulence. At the end, development direction in the future is prospected..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 105007 (2012)
Modulation Technology of the Visible Light Parallel Communication System Based Upon 2D-Bar Code
Chen Zhiping, Liang Zhongcheng, Ma Zhengbei, Qian Chen, and Cao Jie
In order to make the visible light parallel communication system that is based upon LED arrays more perfect, and explore a suitable modulation technology, some experiments have been conducted and some conclusions are gotten. According to the feature of the visible light parallel communication system and quick response In order to make the visible light parallel communication system that is based upon LED arrays more perfect, and explore a suitable modulation technology, some experiments have been conducted and some conclusions are gotten. According to the feature of the visible light parallel communication system and quick response two dimensional (QR 2D) bar code, QR code is used as the information transmit mode of the visible light parallel communication system, and then the modulation scheme of the visible light parallel communication system is studied that is based upon 2D-bar code and the decoded techniques of QR code which is transmitted from the LED arrays. The experimental results demonstrate that QR code images can be transmitted dynamically, received expediently and decoded exactly by the way of the image processing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 105008 (2012)
Simulation of 3-bit All Optical Comparator Based on the Cascade SOA-MZIs
Zhang Limei, Wang Zhi, Chen Yingchuan, and Wu Chongqing
All-optical signal processing is a key technology in high speed optical communication network. The label/head processing as a key technology of optic packet smitching can be realized by using the all optical comparator. A 3-bit all optical comparator based on cascaded semiconductor optical amplifier-Mach-Zehnder interfAll-optical signal processing is a key technology in high speed optical communication network. The label/head processing as a key technology of optic packet smitching can be realized by using the all optical comparator. A 3-bit all optical comparator based on cascaded semiconductor optical amplifier-Mach-Zehnder interferometer (SOA-MZI) is demonstrated at 10 Gb/s by simulation. An extinction ratio of 48 dB and peak power values higher than 7 mW are found at the output. A fall width at half maximum (FWHM) of 8.5 ps is obtained for the output pulses from the comparator. The output pulses have a high intensity and a high stability..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 105009 (2012)
Tunable Photonic Crystal Filter Based on Acousto-Optic Interaction
Wu Hao, Xu Fei, and Lu Yanqing
A way is proposed to modulate light propagation in one dimension photonic crystal with acoustic wave. The transfer matrix method is induced to calculate the reflective spectrum and acousto-optic interaction in a fiber Bragg grating (FBG). It is approved that sideband wavelength and reflectivity can be fine adjusted by A way is proposed to modulate light propagation in one dimension photonic crystal with acoustic wave. The transfer matrix method is induced to calculate the reflective spectrum and acousto-optic interaction in a fiber Bragg grating (FBG). It is approved that sideband wavelength and reflectivity can be fine adjusted by changing the acoustic wave. The result shows a 30 ps group delay is achieved on a 10 cm FBG. This method can be applied to novel devices of photonic crystal such as tunable filters..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 105010 (2012)
Method of assisting the fabrication process of holey fiber based on combination model of digital image processing and finite element method
Wenliang Lu, Shuqin Lou, Liwen Wang, and Weiguo Chen
In the fabrication process of holey fiber, the final geometry of the actual fiber usually deviates from the ideal. We propose a novel method based on the combination of digital image processing technique and finite element method to model the optical properties of the actual fiber rapidly. A polarization-maintaining hoIn the fabrication process of holey fiber, the final geometry of the actual fiber usually deviates from the ideal. We propose a novel method based on the combination of digital image processing technique and finite element method to model the optical properties of the actual fiber rapidly. A polarization-maintaining holey fiber reported by crystal fiber A/S has been modeled and its numerical results accord with the parameters given by the data. Experimental result demonstrates that the optical properties of the fiber can be analyzed rapidly so that the draw parameters can be adjusted in time..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 105011 (2012)
Fiber Nonlinearity Impairment for Coherent Optical Orthogonal Frequency-Division Multiplexing Systems with Midlink Optical Phase Conjugation
Liu Xuejun, Luan Haiying, Dai Bo, and Lan Bo
Due to high peak-to-average power ratio (PAPR) and the nearest subcarrier spacing, fiber nonlinearity impairment becomes the determining factor of coherent optical orthogonal frequency-division multiplexing (CO-OFDM) systems. Midlink optical phase conjugation (M-OPC) is used to compensate for the fiber Kerr nonlinearitDue to high peak-to-average power ratio (PAPR) and the nearest subcarrier spacing, fiber nonlinearity impairment becomes the determining factor of coherent optical orthogonal frequency-division multiplexing (CO-OFDM) systems. Midlink optical phase conjugation (M-OPC) is used to compensate for the fiber Kerr nonlinearity effect in CO-OFDM systems. Because of the symmetry of both ends of the link, OPC can best meet the conditions of compensation and has best nonlinearity compensation effect. And OPC can be applied to link with and without online dispersion compensation. Through OPC for 40 Gb/s single channel system, the maximum Q can be increased by 3 dB, and the nonlinear threshold (NLT) (for Q>10 dB) is increased by 4 dB. For wavelength division multiplex (WDM) system, the maximum Q can be increased by 3 dB and NLT is increased by 1 dB..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 105012 (2012)
Mode Characteristics of Liquid Crystal Filled Photonic Crystal Fiber in Electric Field Sensing
Yang Yang, Dai Haitao, Sun Xiaowei, and Yao Jianquan
Optical guiding characteristics of photonic crystal fibers (PCF) can be tuned by varying the parameters of air holes (diameter, distance and arrangement) and filling dielectric materials. Liquid crystal is one promising material used as the filling agent in PCF due to its electrical tunability, which can lead to the elOptical guiding characteristics of photonic crystal fibers (PCF) can be tuned by varying the parameters of air holes (diameter, distance and arrangement) and filling dielectric materials. Liquid crystal is one promising material used as the filling agent in PCF due to its electrical tunability, which can lead to the electrically tunable PCFs. Finite element method (FEM) is used to explore the effective refractive indices and effective areas of fundamental modes of PCF filled with liquid crystal (E7) as functions of duty cycles and voltages. Both the cut off voltages under variable duty cycles and cut off wavelengths under constant voltages are obtained for fundamental modes. Numerical results also show that cut off voltages increase as the duty cycles increasing, meanwhile the tunable wavelength range decreases as voltages increasing under constant duty cycles. PCFs filled with liquid crystal are expected in the application of electric field sensing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 105013 (2012)
Quantum Optics
Electromagnetically Induced Self-Imaging in the Hot Atomic Medium
Wang Chunfang, and Guo Hongju
The approximate gradient index is formed under the condition of electromagnetically induced transparency (EIT) in the hot atomic medium. Theoretical study shows that, self-imaging can also be induced after considering Doppler broadening. With the split-step Fourier medthod and lattice matrix, normalized intensity distrThe approximate gradient index is formed under the condition of electromagnetically induced transparency (EIT) in the hot atomic medium. Theoretical study shows that, self-imaging can also be induced after considering Doppler broadening. With the split-step Fourier medthod and lattice matrix, normalized intensity distribution on the transverse transmission plane is studied. With the definition of difference factor of image plane, the location of the self-imging can be calculated accurately. The influences of the temperature on the position of the self-imaging and the corresponding imaging quality are discussed in detail. Numerical results show that, with the increase of the temperature, the location of the self-imaging linearly moves away from the original object, and the self-imaging quality decreases..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 118001 (2012)
Remote Sensing and Sensor
Temperature-Independent Humidity Sensor Based on Polarization Maintaining Fiber Loop Mirror
Liang Houhui, Jin Yongxing, An Jiali, Wang Jianfeng, and Dong Xinyong
A relative humidity sensor based on two polarization maintaining fibers loop mirror with temperature compensation is presented. The proposed sensor is created through coating a thin layer of polyvinyl alcohol onto a polarization maintaining fiber from which a portion of the cladding is etched, and the other polarizatioA relative humidity sensor based on two polarization maintaining fibers loop mirror with temperature compensation is presented. The proposed sensor is created through coating a thin layer of polyvinyl alcohol onto a polarization maintaining fiber from which a portion of the cladding is etched, and the other polarization mainting fiber is used to compensate temperature. The relative humidity optical fiber sensor which shows a linear response to parameter and compensates for temperature is tested with different surrounding humidity levels from 20% to 80%. Experimental results show that the sensitivity of the relative humidity measurement is 0.98 nm/% (RH) and the effect of temperature sensitivity is only 0.0072 nm/℃. The goal to offset the effect of temperature is experimentally achieved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 114001 (2012)
Distributed Optical-Fiber Sensor Combining Brillouin Optical Time Domain Analyzer with Mach-Zehnder Interferometer
Xie Hang, Song Muping, Shen Yiming, Dong Peijun, and Ye Xianfeng
Brillouin distributed optical fiber sensor is suitable for measuring the static temperature/strain, but Mach-Zenhder interferometer distributed optical fiber sensor (DOFS) can be used to measure the dynamic strain. Many practical applications need static and dynamic sensing information, which is beyond the capability oBrillouin distributed optical fiber sensor is suitable for measuring the static temperature/strain, but Mach-Zenhder interferometer distributed optical fiber sensor (DOFS) can be used to measure the dynamic strain. Many practical applications need static and dynamic sensing information, which is beyond the capability of the single mechanism distributed optical fiber sensor. Considering optical-fiber sensors of Brillouin optical time domain analyzer (BOTDA) and optical-fiber sensors of Mach-Zenhder interferometer are both using the loop sensing fiber structures, BOTDA and Mach-Zenhder interference are combined together by sharing with the same sensing optical fiber, light source, and other optical devices. BOTDA is used to measure temperature, and Mach-Zenhder interferometer is applied to measure vibration. So, the sensor with multi-mechanism and multi-parameter can be achieved. A preliminary 25 km sensing experiment system is built for testing. For Mach-Zenhder′s vibration sensing, spatial accuracy can reach to 60 m, and the vibration frequency is able to be obtained. For BOTDA′s temperature testing, the beginning and end′s measurement accuracy are 2 ℃ without vibration in existence, and the accuracy becomes 3 ℃ and 4 ℃ respectively with vibration..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 114002 (2012)
Tilted Fiber Bragg Grating Based Temperature-Independent Vibration Sensor
An Jiali, Liang Houhui, Jin Yongxing, Wang Jianfeng, and Dong Xinyong
A new type fiber vibration sensor based on a tilted fiber Bragg grating (TFBG) interacting with a multimode fiber (MMF) is presented. The sensing head is formed by inserting a small section of MMF into a sing-mode fiber and the TFBG. The reflection light from this titled fiber Bragg grating includes two parts, the reflA new type fiber vibration sensor based on a tilted fiber Bragg grating (TFBG) interacting with a multimode fiber (MMF) is presented. The sensing head is formed by inserting a small section of MMF into a sing-mode fiber and the TFBG. The reflection light from this titled fiber Bragg grating includes two parts, the reflected Bragg mode and cladding modes. The cladding modes are coupled back into core mode as a function of the multimode fiber. The power of the cladding modes is sensitive to the vibration, so the external vibration measurement can be obtained through the average output power of cladding mode. The sensor device is simple due to the usage of the intensity demodulation method. The experimental results show that the root mean square (RMS) detection error of the average power is 0.01 μW within the temperature range from 20 ℃ to 70 ℃, so it is proved to be temperature independent..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 114003 (2012)
A Humidity Sensor Based on All-Fiber Fabry-Perot Interferometer Formed by Large Offset Splicing
Yao Jun, Zhu Tao, Deng Ming, Rao Yunjiang, and Duan Dewen
A novel humidity sensor based on open cavity Fabry-Perot (F-P) interferometer which is formed by fusion splicing a short section of single-mode fiber (SMF) between two sections of single-mode fibers with a large offset splicing method is proposed. The proposed structure can act as a nano-composite hygrometer with high A novel humidity sensor based on open cavity Fabry-Perot (F-P) interferometer which is formed by fusion splicing a short section of single-mode fiber (SMF) between two sections of single-mode fibers with a large offset splicing method is proposed. The proposed structure can act as a nano-composite hygrometer with high sensitivity by filling the cavity with a humidity sensitive material polyacrylamide (PAM). It is realized that the humidity can be measured by monitoring the interference spectrum shift of the sensor when the refractive index of PAM changes due to absorbing water vapor in the air substantially. The experimental results show that the interference spectrum shift is about 4 nm when the surrounding humidity varies in the range of 38%~78% and the sensitivity of interference spectrum shift versus the relative humidity is about 0.1 nm/%; the interference spectrum shift can reach up to about 59 nm when the surrounding humidity varies in the range of 88%~98% and the sensitivity of interference spectrum shift versus the relative humidity is 5.868 nm/%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 114004 (2012)
High-sensitivity pressure sensor based on tilt fibre Bragg grating radial load effect
Qi Jiang
In this paper, a simple and novel optical fibre pressure sensor with tilt fibre Bragg grating is put forward. The radial compression and rebound on tilt fibre Bragg grating (TFBG) cause grating angle and length change, meanwhile, its cladding mode spectra decrease sharply. Some transmission spectrum characteristics, suIn this paper, a simple and novel optical fibre pressure sensor with tilt fibre Bragg grating is put forward. The radial compression and rebound on tilt fibre Bragg grating (TFBG) cause grating angle and length change, meanwhile, its cladding mode spectra decrease sharply. Some transmission spectrum characteristics, such as amplitude, extinction ratio value, wavelengths of cladding and Bragg modes, are extracted and analyzed. It shows that they are nearly linear with the radial pressure on surface of bare TFBG. Among them, the extinction ratio value with high sensitivity of 0.7 dB/N can keep consistent with pressure. The max amplitudes of some cladding mode resonance are good linear with radial press with sensitivity of 0.18 dB/N. The relation between each mode resonance wavelength shift and radial press on TFBG keeps good linearity with 0.8-pm/N sensitivity. By means of choosing tygon elastic pad material imposed on bare TFBG, the pressure sensitivity with amplitude of 0.21 dB/N and extinction ratio of 0.25 dB/N is obtained in order to use in practical engineering..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 114005 (2012)
A Strain Sensor Based on In-Line Mach-Zehnder Interferometer with Thin-Core Fiber
Sun Miao, Xu Ben, and Li Yi
A optical fiber strain sensor based on in-line Mach-Zehnder interferometer is proposed. The in-line Mach-Zehnder interferometer is fabricated by simply splicing a section of thin-core fiber between two single-mode fibers (SMFs). When the light couples into the thin-core fiber, part of the light couples into the core ofA optical fiber strain sensor based on in-line Mach-Zehnder interferometer is proposed. The in-line Mach-Zehnder interferometer is fabricated by simply splicing a section of thin-core fiber between two single-mode fibers (SMFs). When the light couples into the thin-core fiber, part of the light couples into the core of the thin-core fiber and propagates as the core mode. While part of the light couples into the cladding of the thin-core fiber, and many cladding modes are excited. The lights at the core mode and the cladding modes in the thin-core fiber are prone to interference when recoupling into the SMF. By interrogating the wavelength shifts of the interference spectrum, the strain sensor is demonstrated. A strain sensitivity of -1.83 pm/με is achieved within the measurement range from 0 to 2000 με. The experimental results agree well with theoretical analyses. This strain sensor has the advantages of small size, simple fabrication, and high sensitivity..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 114006 (2012)
Image denoising algorithm based on even step-length generalized cross validation model
Libao Zhang, and Kaina Yang
Generalized cross validation (GCV) is a significant mean square error (MSE) estimator. It is widely used for image denoising because it can provide an optimal denoising threshold for these wavelet coefficients of noise image. However, the computational complexity of GCV is higher than that of the universal threshold deGeneralized cross validation (GCV) is a significant mean square error (MSE) estimator. It is widely used for image denoising because it can provide an optimal denoising threshold for these wavelet coefficients of noise image. However, the computational complexity of GCV is higher than that of the universal threshold denoising algorithm. In this study, an efficient and fast image denoising algorithm is proposed based on even step-length (ESL) GCV model. In ESL-GCV model, only the thresholds on even points are calculated from four to the maximum wavelet coefficient. In addition, the ESL-GCV model is optimized using the integer wavelet transform (IWT). These experimental results show that the IWT-based ESL-GCV model can provide lower computational complexity and the better peak signal-to-noise ratio (PSNR) than those of the traditional GCV. The proposed algorithm has important theoretical and practical value for image denoising in the future..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 114007 (2012)
Liquid Level Sensor Based on a Single-Mode Hetero-Core Fiber Structure
Xu Ben, Li Yi, Sun Miao, and Zhao Xiaowei
A novel liquid level sensor is proposed. A segment of thin-core single-mode fiber (TCSMF) is inserted in a single-mode fiber (SMF) by splicing to form an in-line Mach-Zehnder interferometer (MZI). The phase difference between cladding modes and core mode is changed with the change of liquid level, and then the transmisA novel liquid level sensor is proposed. A segment of thin-core single-mode fiber (TCSMF) is inserted in a single-mode fiber (SMF) by splicing to form an in-line Mach-Zehnder interferometer (MZI). The phase difference between cladding modes and core mode is changed with the change of liquid level, and then the transmission spectrum of MZI is changed. The principle and sensitivity of the sensor are analyzed theoretically, and experimental results show that the shift of the peak wavelength is almost linearly proportional to the change of liquid level and the sensitivity increases with the refractive index (RI) of tested liquid, which is content with the analyzed results. The sensitivities of 0.160 nm/mm and 0.228 nm/mm are obtained in pure water and saturated salt water, respectively. The sensor is characterized by full optical fiber structure, easy fabrication and high sensitivity, and it is promising in measuring accurately the level of liquid with refractive index less than that of cladding..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 114008 (2012)
Measurement of Temperature Profiles above Nanjing Using Raman Lidar
Guo Jingqiu, Bu Lingbing, Wang Ming, Tian Li, Huang Xingyou, and Xia Junrong
The basic structure of Rayleigh-Raman-Mie (RRM) lidar as well as the principle of temperature retrieval algorithm using Raman scattering are introduced. Background correction, slide average and wavelet transform are employed to denoise the Raman backscattering signal, and then the effect of aerosols to temperature profThe basic structure of Rayleigh-Raman-Mie (RRM) lidar as well as the principle of temperature retrieval algorithm using Raman scattering are introduced. Background correction, slide average and wavelet transform are employed to denoise the Raman backscattering signal, and then the effect of aerosols to temperature profile is analyzed. Using the algorithm described, temperature profiles above Nanjing from 5 km to 18 km during 1853 to 1935 on November 19, 2010 are retrieved. The measured results showed that the temperature variation at altitude of 5.5 km is less than 2 K; The entire month of observation data during November 2010 are analyzed and processed, average temperature profiles of three ten days are obtained. At altitude of 10 km, temperature of first ten days is 4 K higher than that of the third ten days. With winter approaching, the temperature lapse rate has significantly increased in low-altitude section. Monthly mean temperature in the range of 5~10 km is 4 K lower than the model value, and the two profiles are almost parallel which showed temperatures at most altitude below 10 km are 4 K lower than that of model..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 114009 (2012)
Study on Coherent Ladar Image Denoising by Block-Matching and 3D Filtering
Xia Zhiwei, Li Qi, Liu Zhengjun, and Wang Qi
Due to the different characteristics between the range and intensity images of ladar, block-matching and 3D filtering (BM3D) is used in both range image and intensity image denoising respectively. And the denoising results are compared and analyzed with those of non-local means (NLM) filtering. The results of experimenDue to the different characteristics between the range and intensity images of ladar, block-matching and 3D filtering (BM3D) is used in both range image and intensity image denoising respectively. And the denoising results are compared and analyzed with those of non-local means (NLM) filtering. The results of experiments show as follows. For intensity image, homostasis BM3D algorithm, which has a better performance in restoring the edge of objects and keeping smoothness in homogeneous area, is better than homostasis NLM algorithm. Generally speaking, preserving right range value is significant for range image processing, so both BM3D and NLM are not sufficient ideal under the circumstance..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 114010 (2012)
Spectroscopy
Influence on X-ray Diffraction by Crystal′s Surface Dislocation Treatment
Wang Hongjian, Li Zeren, Xiao Shali, Ye Yan, and Yang Qingguo
To improve the crystal X-ray diffraction efficiency in wavelength range of 0.1~20 nm, it is processed that crystal surface is dealt with specific technique. Those crystals, such as mica、α-quartz and LiF, are cleaved slice of 80 mm×10 mm, with LiF crystal thickness of 1 mm, other crystals thickness of 0.2 mm. LiF cTo improve the crystal X-ray diffraction efficiency in wavelength range of 0.1~20 nm, it is processed that crystal surface is dealt with specific technique. Those crystals, such as mica、α-quartz and LiF, are cleaved slice of 80 mm×10 mm, with LiF crystal thickness of 1 mm, other crystals thickness of 0.2 mm. LiF crystal is heated up to about 400 ℃, then bended by curved-machine time after time and cooled to room temperature by natural, resulting in a so-called dislocation phenomenon which leads to enhance diffractive efficiency. The experience is carried on a Cu target X-ray diffractometer (XRD) with wavelength of 0.154 nm. Muti-diffractive phenomenon happens on mica spherical surface crystal. Double intensity is achieved on processed LiF crystal surface compared to original crystal. The experimental results show that it is more suitable to diagnose soft X-ray after treating the crystal surface for improving dislocation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 115001 (2012)
Rapidly Changing Phase Error Correction of Fourier Transform Spectrometer
Zhang Peng, and Zhang Zhihui
Rapidly changing phase error correction of interferential fourier transform spectrometer is researched. A complex number is reconstructed, which the real part is the data of zero-crossing single sided interferogram and the imaginary part is the data of short double sided interferogram. After once Fourier transform of tRapidly changing phase error correction of interferential fourier transform spectrometer is researched. A complex number is reconstructed, which the real part is the data of zero-crossing single sided interferogram and the imaginary part is the data of short double sided interferogram. After once Fourier transform of the reconstructed complex number, the method can avoid the serious error caused by polynomial fitting of phase error as the phase error is rapidly changing. Then the high precision spectrum can be obtained, based on the characters of real number Fourier transform and discrete Fourier transform. The simulation results show that when phase error can′t change gradually with wave number, conventional Mertz method can′t correct the phase error which is serious, however, the method which is proposed by this paper can correct the phase error, and can gain perfect spectrum. The new method can be widely applied to spectral reducing of interferential Fourier transform spectrometer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 115002 (2012)
Terahertz Technology
THz Reflection Properties Measurement of Several Kinds of Optical Brackets
Li Yunda, Li Qi, Xue Kai, and Wang Qi
Optical brackets are important parts of a terahertz (THz) experiment system. It is of great significance to improve the experimental accuracy by studying the reflection properties of the common optical brackets and taking proper measures to reduce reflection impacts. In this paper, a variety of common optical brackets,Optical brackets are important parts of a terahertz (THz) experiment system. It is of great significance to improve the experimental accuracy by studying the reflection properties of the common optical brackets and taking proper measures to reduce reflection impacts. In this paper, a variety of common optical brackets, such as a square filter fixed bracket, a triangle block, two stainless steel connected rods and several rod bases et al., are measured in the reflection experiments by using contrast measurement method. The reflectivity of the optical brackets with incident angles of 45° using 2.52 THz laser have been obtained approximately. It can be inferred from the results that the smooth stainless steel connecting rods have a relatively higher reflectivity. The reflectivity of the rod with a diameter of 25 mm is about 43%. For the painting rod base with uneven surface and a diameter of 25 mm, the reflectivity is 0.62%. The reflectivity of the diamond-shaped stripe area of the lift rod base is only 0.35%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 111001 (2012)
Influence of Gaussian Beam on Conductor Cylinder Terahertz Radar Cross Section
Li Huiyu, Li Qi, Xia Zhiwei, Zhao Yongpeng, Chen Deying, and Wang Qi
By measuring radar cross section (RCS) of scale model, the RCS of the full size target at microwave band is acquired. The estimation and measurement of the terahertz radar cross section is one of the most important applications in terahertz technique. In the RCS estimation, usually a plane wave is assumed; while in reaBy measuring radar cross section (RCS) of scale model, the RCS of the full size target at microwave band is acquired. The estimation and measurement of the terahertz radar cross section is one of the most important applications in terahertz technique. In the RCS estimation, usually a plane wave is assumed; while in real measurement, generally a Gaussian beam or a similar beam resource is adopted. The RCS of an infinite perfect conductor cylinder is estimated under the condition that the incident wave is transverse electric wave. In the estimation, the influence of 2.52 THz collimated laser beam and phase variation on backward RCS are studied and the RCS with scattering angle is obtained; at the same time, a comparison between plane wave and Gaussian beam is also given. The estimation results show choosing facula radius 30 mm is appropriate when cylinder radius is 10 mm and the distance between the cylinder and the beam source is 1 m..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 111002 (2012)
Optical properties of selected Chinese Traditional Patent Medicines and Western Medicines terahertz range
Chao Dai, Kun Zhao, Hui Zhao, and Lu Tian
The spectral characteristics of Sang Ju Gan Mao Granules, Gan Mao Jie Du Tablet, Fu Fang Jin Yin Hua Granules and Compound Paracetamol, and Amantadine Hydrochloride Tablets are studied by terahertz time-domain spectroscopy (THz-TDS) technologies in the spectral range of 0.2—1.7 THz. The absorption spectra and the indexThe spectral characteristics of Sang Ju Gan Mao Granules, Gan Mao Jie Du Tablet, Fu Fang Jin Yin Hua Granules and Compound Paracetamol, and Amantadine Hydrochloride Tablets are studied by terahertz time-domain spectroscopy (THz-TDS) technologies in the spectral range of 0.2—1.7 THz. The absorption spectra and the indexes of refraction are obtained. It can be seen that the three samples of Chinese Traditional Patent Medicines have almost the same absorption peaks at 1.44 THz. However, the absorption peaks of the three western medicine samples are at 0.73, 1.01, and 1.18 THz, respectively. The large spectral differences between different drugs are strong evidences that THz time-domain spectroscopy is a useful fingerprint technique in the study of pharmaceutical compounds and the crack down on the fake medicines..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 111003 (2012)
Broadband Tuning Multifunctional Photonic Crystal Fiber for Terahertz Device
Hou Yu, Fan Fei, Wang Xianghui, and Chang Shengjiang
A theoretical study of liquid crystal filled photonic crystal fiber is presented. The effects of electric birefringence of liquid crystal in the liquid crystal filled photonic crystal fiber and the transmitting properties of photonic crystal fiber are investigated by using the full vector plane wave expansion and beam A theoretical study of liquid crystal filled photonic crystal fiber is presented. The effects of electric birefringence of liquid crystal in the liquid crystal filled photonic crystal fiber and the transmitting properties of photonic crystal fiber are investigated by using the full vector plane wave expansion and beam propagation methods. At the same time, finite different time domain method is used to calculate the change of liquid crystal molecules with the external electric field. The simulation results show that the electrically controlled liquid crystal filled photonic crystal fiber can act as a terahertz switch with about 0.55 THz bandwidth. It also has low coupling loss and high extinction ratio which is more than 30.78 dB. Furthermore, when the frequency of the incident terahertz wave meets some conditions, the device can control the polarization state of the incident terahertz wave..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 111004 (2012)
Wavelet-Based Autofocus Algorithm for Terahertz Digital Holographic Imaging
Xue Kai, Li Qi, and Wang Qi
Autofocus technique is one of the key techniques in digital hologram, which can achieve fast imagine capture and accurate reconstruction. A new wavelet-based autofocus algorithm for terahertz (THz) digital holographic imaging is proposed based on the analysis of focus and defocus characteristics, which mainly concentraAutofocus technique is one of the key techniques in digital hologram, which can achieve fast imagine capture and accurate reconstruction. A new wavelet-based autofocus algorithm for terahertz (THz) digital holographic imaging is proposed based on the analysis of focus and defocus characteristics, which mainly concentrates on coefficient of high frequency and low frequency wavelet transform. The new autofocus algorithm of this focus measure is compared with five classic digital hologram autofocus algorithms according to the THz image with and without noise, also comments are attached. The analysis and comparison of the simulation show that the new wavelet-based autofocus algorithm has the following features: a better unimodality, a fineness sharpness and a stronger performance of anti-noise..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 39, Issue s1, 111005 (2012)
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