Journals >Chinese Journal of Lasers
Contents
2013
Volume: 40 Issue 9
45 Article(s)
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[in Chinese]
Quantum Key Distribution Analysis for Filtering Scheme Based on Double Fiber Bragg Grating
Zhao Guhao, Zhao Shanghong, Yao Zhoushi, Hao Chenlu, Meng Wen, Wang Xiang, Zhu Zihang, and Liu Feng
A strict express of signal sideband in the polarization coding subcarrier multiplexing quantum key distribution scheme is presented. The source of quantum bit error rate in the modulation process is analyzed. A filtering scheme based on double fiber Bragg grating (FBG) for the polarization coding subcarrier multiplexinA strict express of signal sideband in the polarization coding subcarrier multiplexing quantum key distribution scheme is presented. The source of quantum bit error rate in the modulation process is analyzed. A filtering scheme based on double fiber Bragg grating (FBG) for the polarization coding subcarrier multiplexing quantum key distribution is presented. The reflection ends of these two FBG are placed toward each other. The reflection spectra are used to filter out the signal frequency from clutter frequency. The simulation results show that, the reflection structure can filter the intermodulation sideband except signal frequency and decrease the quantum bit error rate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 918001 (2013)
Study on the Measurement Matrix in Intensity Correlation Imaging Laser Radar
Cui Lijun, Zhao Chengqiang, Xu Wendong, and Jiao Jia
Under the framework of ghost imaging via sparsity constraints (GISC), we do numerical simulations on the influence of the speckle intensity distribution on image quality and study the relationship between the sampling number needed for information reconstruction and the speckle size and the target sparsity. Numerical sUnder the framework of ghost imaging via sparsity constraints (GISC), we do numerical simulations on the influence of the speckle intensity distribution on image quality and study the relationship between the sampling number needed for information reconstruction and the speckle size and the target sparsity. Numerical simulation results show that, the speckle intensity distribution affects the imaging resolution. Gauss distribution is better than flat-topped distribution with the same speckle size, and the Gauss distribution is more suitable for practical application. In addition, when the speckle size is smaller than the resolution of the image, the sampling number required is only related to the image sparse degree, and it has nothing to do with the specific distribution of the image. When the speckle size exceeds the target resolution, to obtain the same image quality (based on the image with lower resolution), the sampling number needs to be inversely proportional to the square of the speckle diameter. The relationship between sampling number and the target sparsity is simulated and verified, while we give and verify the calculation formula of the sparse degree of the natural target with gray..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 918002 (2013)
[in Chinese]
Study of Single Mode-Multimode-Single Mode Refractive Index Sensor Based on No Core Fiber
Chen Yaofei, Han Qun, He Yang, Liu Tiegen, and Hong Chengqing
A fiber sensor based on the single mode-multimode-single mode (SMS) structure for refractive index (RI) sensing is proposed. A kind of no core fiber is used as the multimode waveguide. Compared with the conventional SMS with an etched multimode fiber, the proposed sensor is easy to design and fabricate. A model RI sensA fiber sensor based on the single mode-multimode-single mode (SMS) structure for refractive index (RI) sensing is proposed. A kind of no core fiber is used as the multimode waveguide. Compared with the conventional SMS with an etched multimode fiber, the proposed sensor is easy to design and fabricate. A model RI sensor based on the proposed structure is designed and experimentally tested with sucrose solutions with different RI values. The results show that the sensitivity of the sensor is 431.4 nm/RIU on average in the range of 1.356~1.392. The experimental results agree well with the simulation results. Besides, computer simulation is also performed to systematically analyze the sensor′s characteristics. The results show that the sensitivity of the sensor can be improved by reducing the diameter of the no core fiber..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 905001 (2013)
High Precision and Wide Scale Fiber Bragg Grating Sensor Interrogation System Based on Tunable Filter
Li Jinming, Ma Youchun, Yan Shubin, Liu Hongyu, Ran Zibo, and Su Shuqing
A high precision and wide scale fiber Bragg grating (FBG) sensor interrogation system based on fiber Fabry-Perot tunable filter (FFP-TF) is demonstrated. By dynamic tracking and locking of the driving voltage of FFP-TF, the output wavelength of the laser is locked at the -3 dB reflectivity spectrum of the FBG. A temperA high precision and wide scale fiber Bragg grating (FBG) sensor interrogation system based on fiber Fabry-Perot tunable filter (FFP-TF) is demonstrated. By dynamic tracking and locking of the driving voltage of FFP-TF, the output wavelength of the laser is locked at the -3 dB reflectivity spectrum of the FBG. A temperature immune Fabry-Perot international telecommunication union filter is used as the reference channel. The interpolation algorithm is then used to realize high precision interrogation of dynamic strain. This design resolves the conflict between resolution and measurement scale in interrogation system based on optical filter. A high resolution better than 2 pm within wide strain measurement range is verified by experiments. The polynomial result of FBG spectrum is 0.998..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 905002 (2013)
High Birefringence and Low Confinement Loss Photonic Crystal Fiber with Multiple Zero Dispersion Points Based on Micro-Structured Core
Cao Ye, Wang Jiangyun, and Tong Zhengrong
A new kind of micro-structured core photonic crystal fiber with a rectangular array of ten air holes in the core region and the incremental cladding is proposed. Using the finite element method, the fundamental mode field, birefringence, confinement loss and dispersion characteristics are investigated simultaneously byA new kind of micro-structured core photonic crystal fiber with a rectangular array of ten air holes in the core region and the incremental cladding is proposed. Using the finite element method, the fundamental mode field, birefringence, confinement loss and dispersion characteristics are investigated simultaneously by changing the radii and pitches of the air holes in the core. Numerical results show that the birefringence and confinement loss are respectively about 3.22×10-2 and 4.92×10-8 dB/m at 1.55 μm when the small air hole radius is 0.225 μm and the cladding air hole pitch size is 1.30 μm, and three corresponding zero dispersion points can be obtained over the wavelength range from 0.6 μm to 2.0 μm. In addition, the largest birefringence can reach up to 3.45×10-2 and the confinement loss reduces down to 2.88×10-9 dB/m by optimizing the structural parameters. The proposed photonic crystal fiber has a broad prospect of applications in fiber-optic communications, fiber optic sensing and other fields..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 905005 (2013)
Biomedical Photonics and Laser Medicine
Signal Enhancement and Despeckling of Port Wine Stains Using Optical Coherence Tomography
Yin Daiqiang, Wang Chengming, and Gu Ying
Diameter and depth of dilated blood vessels are two key parameters of port wine stain (PWS) lesions. Recently, optical coherence tomography (OCT) has demonstrated considerable promise for clinical test and the key parameters extraction of PWS. However, intensity attenuation in depth and speckle noise in OCT images consDiameter and depth of dilated blood vessels are two key parameters of port wine stain (PWS) lesions. Recently, optical coherence tomography (OCT) has demonstrated considerable promise for clinical test and the key parameters extraction of PWS. However, intensity attenuation in depth and speckle noise in OCT images constitute two primary limiting factors with respect to resolving the morphologic information of the PWS lesions. In order to enhance the visual quality of the OCT images, we develop new image speckle reduction algorithms for the OCT signal. In the study, epidermis segmentation is based on a dynamic programming scheme; according to the epidermal boundary curve as a baseline, the details in the deep are enhanced by the attenuation compensation. The visual inspection of the enhanced images is then improved by a new variation model that combines the regularization term with the statistical characteristic constraints (Rayleigh distribution) of data corrupted by OCT speckle noise to eliminate the corresponding multiplicative noise. The result shows that the proposed algorithm provides significant improvements of the edge information about the obtained PWS OCT images of dilated blood vessels, which is helpful to divide and extract the key parameters..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 904001 (2013)
Holography and Information Processing
Experimental Study on the Phase-Contrast Imaging of the Living Hippocampal Neuron Cells by Digital Holographic Microscopy
Ouyang Liting, Wang Dayong, Zhao Jie, Wang Yunxin, and He Qihua
In accordance with the need of observing and analyzing living cells, based on the pre-magnification off-axis digital holographic theory, an inverted setup of pre-magnification off-axis image plane digital holographic microscopy is designed and built, where the image plane of the microscope objective is coplanar with thIn accordance with the need of observing and analyzing living cells, based on the pre-magnification off-axis digital holographic theory, an inverted setup of pre-magnification off-axis image plane digital holographic microscopy is designed and built, where the image plane of the microscope objective is coplanar with the recording plane of the hologram. Therefore, the step of the numerical diffraction propagation by the computer is needless and the numerical reconstruction is simplified. Meanwhile, the simple and fast surface fit method is applied to correct the phase aberration. Furthermore, the actual resolution is measured by using the USAF resolution mask, which is 0.87 μm. Finally, the quantitative phase-contrast images of the living hippocampal neuron cells in the natural state are achieved. From the experimental results, the structures of cells including the cell body and the dendrite are observed. The basic parameters of the cell morphology are also obtained. The results show that the digital holography is useful in the quantitative morphological detection of living cells and it provides a non-destructive phase-contrast imaging approach for the cell morphological analysis in the field of the bio-medical research..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 909001 (2013)
Laser Manufacturing
Process Optimization of Thick Nanostructured Ceramic Coating by Laser Multi-Layer Cladding Based on Neural Network and Genetic Algorithm
Wang Dongsheng, Yang Youwen, Tian Zongjun, Shen Lida, and Huang Yinhui
Combination of back propagation (BP) neural networks and genetic algorithm (GA) is used to optimize process parameters of the thick nanostructured Al2O3-13%TiO2 (mass fraction) ceramic coating prepared by laser multi-layer cladding technique. The neural model is trained based on the experimental results of the orthogonCombination of back propagation (BP) neural networks and genetic algorithm (GA) is used to optimize process parameters of the thick nanostructured Al2O3-13%TiO2 (mass fraction) ceramic coating prepared by laser multi-layer cladding technique. The neural model is trained based on the experimental results of the orthogonal test including three factors and three levels. It is developed to express the relationship between coating properties (bonding strength and microhardness) and process parameters (closed-loop controlling temperature of molten pool, ultrasonic vibration frequency and preheating temperature of incubator). Meanwhile, the bonding strength and microhardness of the nanostructured ceramic coating are optimized by single-objective and multi-objective optimization methods based on the genetic algorithms. The results show that the prediction data of genetic neural networks model agree well with the experimental values, and the relative error is less than 2.5%. The maximum bonding strength and microhardness of the coating are 70.7 MPa and 2025.5 HV, respectively. The process parameters of closed-loop controlling temperature in molten pool, ultrasonic vibration frequency and preheating temperature in incubator are set to 2472.0 ℃, 31.9 kHz and 400 ℃ when the bonding strength and microhardness have the same weight. At this state, the overall performance of the coating is the best and the bonding strength and microhardness of the coating are 69.1 MPa and 1835.5 HV, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 903001 (2013)
Fabrication of Light Trapping Microstructures on Stainless Steel Surface by Nanosecond Laser
Wu Bo, Zhou Ming, Li Baojia, and Cai Lan
The micropore array structure is fabricated by nanosecond laser on 316L stainless steel surface. The microstructured metal surface shows a great absorption enhancement with a wavelength range of 200~900 nm. The diameters and heights of the micropores depend on the single laser pulse energy and laser pulse number. With The micropore array structure is fabricated by nanosecond laser on 316L stainless steel surface. The microstructured metal surface shows a great absorption enhancement with a wavelength range of 200~900 nm. The diameters and heights of the micropores depend on the single laser pulse energy and laser pulse number. With the increase of the laser pulse number, the depth/diameter ratio of the micropore increases, and the ratio tends to be stable when the pulse number is more than 1200. With the same pulse number, the weaker the single pulse energy is, the larger the depth/diameter ratio is. The optical absorption properties of the microstructures are estimated by the surface light reflectivity test. For the same ratio of the micropore projected area to the total area and the same pulse number, the lower the single pulse energy is, the stronger the light trapping ability of the micropore array structure is. The formation mechanisms of the micropores and the roles of these micropores in changing metal-surface optical absorption are preliminarily discussed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 903002 (2013)
Laser Ignition Characteristics of Mixtures of Aluminium Powder and Explosives
Hao Haixia, Yao Ergang, Zhao Fengqi, Xu Siyu, Gao Hongxu, and Pei Qing
Ignition characteristics of the mixtures of Al powder and pure RDX, HMX and CL-20 are studied by using CO2 laser with a wavelength of 10.6 μm, and the effects of the Al granularity, the ratio of Al to RDX and different explosives of the mixtures on ignition characteristics of the mixtures are discussed under different Ignition characteristics of the mixtures of Al powder and pure RDX, HMX and CL-20 are studied by using CO2 laser with a wavelength of 10.6 μm, and the effects of the Al granularity, the ratio of Al to RDX and different explosives of the mixtures on ignition characteristics of the mixtures are discussed under different laser heat fluxes. The results show that the ignition of the mixtures tested appears on the surface of the sample, and the ignition time delays of the mixtures gradually decrease with the increase of the laser flux. The effects of Al granularity and the ratio of Al to RDX on the sample igintion are larger at lower laser fluxes and slightly weaken with the laser flux increasing. The delay time of the mixture containing aluminium nano-powder is shorter than that of the mixture containing aluminium micro-powder, and the ignition process is more drastic. The order of the delay time of the mixtures of nano-alumimium with RDX (M-QR), HMX (M-QH) and CL-20 (M-QCL) is tM-QR>tM-QH>tM-QCL and the order of the minimum ignition energy is EM-QR>EM-QH>EM-QCL which is defferent from the order of RDX, HMX and CL-20 that is EHMX
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 903003 (2013)
Wear Resistance of 12CrNi3A Steel after Carburization and Laser Shock
Li Yuqin, Li Yinghong, He Weifeng, Li Jing, Zhang Feng, and Zhou Liucheng
In order to improve the carburized layer quality and wear performance of 12CrNi3A-steel, a combined method of laser shock processing carburization is put forward. The wear performances of different samples which are directly carburized and carburized after laser shock processing are measured by the ball milling experimIn order to improve the carburized layer quality and wear performance of 12CrNi3A-steel, a combined method of laser shock processing carburization is put forward. The wear performances of different samples which are directly carburized and carburized after laser shock processing are measured by the ball milling experiment. The microstructures of 12CrNi3A steel are examined by scanning electron microscope (SEM). The result shows that the wear rate of carburized after laser shock is 2.69×10-14 m3/Nm, reduced by 29% comparing with the samples carburized only. The mechanism of wear resistance improvement is discussed from two aspects. For one thing, the friction coefficient reduces by 25% after laser shock processing and carburization. For another, a large number of fine carbide particles on carburized layer are formed in the sample carburized after laser shock, and the surface carbide particles of 12CrNi3A steel are distributed in a gradient manner..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 903004 (2013)
Laser Cleaning of Contaminations on the Surface of Stone Relics
Ye Yayun, Qi Yang, Qin Lang, Jiang Yong, Xiao Kaibo, Wang Haijun, Luan Xiaoyu, Cheng Xiaofeng, and Yuan Xiaodong
In the fields of cultural relic protection, the diseases on the surface of stone relics affect the conservation and artistic quality of relics. The cleaning methods must be investigated to solve the problem. Compared with the conventional cleaning methods (e.g., chemistry cleaning and sand blasting), laser cleaning is In the fields of cultural relic protection, the diseases on the surface of stone relics affect the conservation and artistic quality of relics. The cleaning methods must be investigated to solve the problem. Compared with the conventional cleaning methods (e.g., chemistry cleaning and sand blasting), laser cleaning is characterized by cleaning objects without damage, strong decontaminaton ability, precise removal, avoiding pollution environments. In the paper, laser cleaning is used for removing the contaminations on the surface of stone relics. Firstly, laser induced damage experiments are carried out. The results show that the laser induced damage threshold of the sandstones is about 73.5 mJ for 1064 nm laser after 10 laser pulses. Meanwhile, the finite element analysis software is used to calculate the temperature and the stress of the sandstones under the laser irradiation. The simulated results are consistent with the experimental ones. The optimal methods and laser parameters are achieved in the laboratory experiments for removal of the ink contamination. The experiments of Bishui temple located in Sichuan province indicate that the laser cleaning is safe and effective for the removal of black smudges..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 903005 (2013)
Study on Laser Dots Marking Based on Dynamic Focusing Galvanometer System
Yan Hengfeng, Chen Jimin, and Shao Jun
The light guide plate (LGP) as the backlight of the liquid crystal display (LCD), has been applied widely. The manufacturing principle arranging the reflection point on the surface of the the LGP material. Currently LGP for lighting is manufactured by screen printing and laser engraving. Laser engraving is more personaThe light guide plate (LGP) as the backlight of the liquid crystal display (LCD), has been applied widely. The manufacturing principle arranging the reflection point on the surface of the the LGP material. Currently LGP for lighting is manufactured by screen printing and laser engraving. Laser engraving is more personalized, flexible and green, but the traditional laser engraving way, whose efficiency is too low, is lack of processing optimization. A methodology of laser dots marking that based on dynamic focus galvanometer system is proposed.The corresponding process optimization method is developed. It improves the effectiveness and efficiency of processing significantly..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 903006 (2013)
Laser Physics
Research on Optical Chirp Linearization Technique of Semiconductor Lasers by an Optoelectronic Feedback Loop
Wu Ying, Chen Dijun, Sun Yanguang, Cai Haiwen, and Qu Ronghui
The research on chirp linearization of a semiconductor laser using an optoelectronic feedback loop is reported. Self-homodyne detection is adopted to characterize the chirp nonlinearities. The beat signal is fed to a frequency discriminator circuit, which measures the laser instantaneous frequency deviation from a perfThe research on chirp linearization of a semiconductor laser using an optoelectronic feedback loop is reported. Self-homodyne detection is adopted to characterize the chirp nonlinearities. The beat signal is fed to a frequency discriminator circuit, which measures the laser instantaneous frequency deviation from a perfectly linear chirp and provides an error signal. The error signal is fed back to the modulation current of the laser, and thus an optoelectronic feedback loop is achieved and linear tuning is realized. The experiment is conducted with a 1550 nm distributed feed back (DFB) laser. The injection current is modulated by a ramp with 20 mA in amplitude and 30 ms in period. A linear tuning range of 10 GHz is realized in experiment. The system is both stable and effective. This technique is of significance to applications such as frequency-modulated continuous-wave laser radar, optical frequency-domain reflectometry etc..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 902001 (2013)
Influence of Relative Carrier Envelope Phases on Attosecond Pulse Generation from CO Molecule Exposed to a Combined Field of Lasers
Liu Lu, Zhao Songfeng, Li Pengcheng, and Zhou Xiaoxin
We theoretically study the high-order harmonic generation and attosecond pulse generation of CO molecule exposed to a two-color combined field composed of 800 nm and 2000 nm laser pulses based on the strong field approximation, where the effect of linear Stark shift on molecular energy levels is considered. The two-colWe theoretically study the high-order harmonic generation and attosecond pulse generation of CO molecule exposed to a two-color combined field composed of 800 nm and 2000 nm laser pulses based on the strong field approximation, where the effect of linear Stark shift on molecular energy levels is considered. The two-color combined field can be efficiently controlled by optimizing their relative carrier envelope phases. The results show that the cut-off of harmonics is significantly extended in the combined field, and the supercontinuum of harmonics is apparently improved due to the ionization suppression of asymmetric molecule in a certain direction, which leads to the decrease of quantum interference during the propagation of the continuum electron. By superimposing several harmonics of the plateau region, the isolated attosecond pulse can be obtained for several relative phases, and the shortest pulse achieves 98 as. The width of attosecond pulse is obviously shortened compared with the situation that CO molecule is driven by a one-color laser field..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 902002 (2013)
Research on Three-Wavelength Diode Pumped Solid State Laser of 0.5 μm Waveband
Shao Zhiqiang, Gao Lanlan, Tan Huiming, and Zhang Chen
In order to improve the stability of the 561 nm yellow laser output power by the Nd:YAG/LBO intra-cavity frequency doubling, the birefringence filter (BF) is inserted into cavity. Meanwhile, the 556 nm and 558 nm single line laser outputs are obtained by tuning the alignment angle of the BF. When the pumping power of NIn order to improve the stability of the 561 nm yellow laser output power by the Nd:YAG/LBO intra-cavity frequency doubling, the birefringence filter (BF) is inserted into cavity. Meanwhile, the 556 nm and 558 nm single line laser outputs are obtained by tuning the alignment angle of the BF. When the pumping power of Nd:YAG crystal is 5 W, and the thickness of BF is 2 mm, the fundamental beam of the single line laser is obtained by tuning the alignment angle of the BF. Then, the yellow laser is obtained by LBO intracavity-frequency-doubling. At the incident pumping power of 5 W, the output power at 556, 558, 561 nm are 256, 189, 227 mW, and the corresponding light-to-light conversion efficiency are 5.12%、3.78% and 4.54%, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 902003 (2013)
Study on Temperature Distribution of Disk-Type Laser Based on Heat-Fluid-Solid Multiphysics Coupling Method
Yang Huomu, Feng Guoying, Wei Yongtao, Mu Jian, Wang Shutong, Wang Shaopeng, Tang Chun, and Zhou Shouhuan
Based on the heat-fluid-solid multiphysics coupling method, the fluid flow, convective diffusion and thermal conduction, which occur in the pumping and cooling processes of high power disk-type laser, are simulated and analyzed. Influences of pumping power and fluid flowing velocity on the temperature distribution of dBased on the heat-fluid-solid multiphysics coupling method, the fluid flow, convective diffusion and thermal conduction, which occur in the pumping and cooling processes of high power disk-type laser, are simulated and analyzed. Influences of pumping power and fluid flowing velocity on the temperature distribution of disk gain medium are studied. Simulation results reveal that the temperature of cooling fluid gradually increases in the fluid flowing direction under the interaction of flowing, heat conduction and convective diffusion. Temperature distribution of the laser gain medium is asymmetrical in the direction of fluid flowing direction. The highest temperature position on the flowing direction is shifted from the axis of gain medium. A linear variation of temperature differences on the flowing direction of gain medium between the inlet and outlet is showed with the pump power increasing. A nonlinear variation of temperature difference on the flowing direction of gain medium between the inlet and outlet is showed with the fluid flowing velocity increaseing. Experimental results are in agreement with the simulation results..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 902004 (2013)
A Frequency Tuning and Locking System of a Deep UV Laser for Laser Cooling of Mercury Atoms
Liu Hongli, Qian Jun, Xu Zhen, and Wang Yuzhu
We develop a power saving frequency tuning and locking system of a deep ultraviolet (UV) laser at 253.7 nm, which will play an important role in a magneto-optical trap for neutral mercury atoms. Combined with two cascade acousto-optical modulators (AOMs) and frequency modulation (FM) spectroscopy in a mercury vapour ceWe develop a power saving frequency tuning and locking system of a deep ultraviolet (UV) laser at 253.7 nm, which will play an important role in a magneto-optical trap for neutral mercury atoms. Combined with two cascade acousto-optical modulators (AOMs) and frequency modulation (FM) spectroscopy in a mercury vapour cell, the deep UV laser can be locked and tuned on 1S0-3P1 transition of Hg atoms, and the power for laser cooling can be saved. FM spectroscopy is also observed by demodulating the saturated absorption spectroscopy (SAS) of the FM laser. The UV laser is well locked on 1S0-3P1 transition of 200Hg atoms with the instability less than 0.1 MHz..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 902005 (2013)
Study on Output Spectral Characteristic of Yb-Doped Fiber Lasers
Liu Wei, Xiao Hu, Wang Xiaolin, and Zhou Pu
Based on self-phase modulation, an analytical model of Yb-doped fiber laser describing its output spectral characteristics has been developed. The output spectral shape, the variation trend of output spectrum along with the increased power, and its characteristics in low-power have been analyzed by experimental measureBased on self-phase modulation, an analytical model of Yb-doped fiber laser describing its output spectral characteristics has been developed. The output spectral shape, the variation trend of output spectrum along with the increased power, and its characteristics in low-power have been analyzed by experimental measurement. As the experimental results show, this analytical model agrees well with the experimental results, and through this model, the variation of the output spectral line width with the variational output power and the spectral characteristics in low power can be accurately obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 902006 (2013)
Study on Output Characteristics of a Passively Mode-Locked Yb-Doped Fiber Laser under Limitation of Finite Gain Bandwidth
Wang Dashuai, Wu Ge, Gao Bo, and Tian Xiaojian
Based on a lumped model of a passively mode-locked Yb-doped fiber laser, the influence of the limited gain bandwidth on the laser′s output characteristics is investigated numerically. Simulation results show that the duration of the output pulse and the operating regimes are determined by the gain bandwidth. The pulse Based on a lumped model of a passively mode-locked Yb-doped fiber laser, the influence of the limited gain bandwidth on the laser′s output characteristics is investigated numerically. Simulation results show that the duration of the output pulse and the operating regimes are determined by the gain bandwidth. The pulse duration increases with the gain bandwidth increasing. By changing the intra-cavity average dispersion monotonically, it is demonstrated that under the condition of wide gain bandwidth, the laser operates in the self-similar regimes under a large range of cavity parameters. In addition, the interaction of pulse pair in distinct gain bandwidth is also studied. Simulation results show that the nonlinear phase shift plays an important role in pulses interaction, and the nonlinear phase shift is determined by the gain bandwidth, therefore the wider gain bandwidth leads to the stronger interaction forces between the pulses..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 902007 (2013)
Study on Ytterbium-Doped Fiber Lasers of Special Wavelength
Xiao Hu, Zhang Hanwei, Wang Xiaolin, Zhou Pu, and Xu Xiaojun
Ytterbium doped fiber lasers of special wavelength are investigated in theory and experiment. The gain competition between signal and amplified spontaneous emission is theoretically investigated based on the absorption and emission characteristics of Yb3+. Available approaches to suppress parasitic oscillation are analYtterbium doped fiber lasers of special wavelength are investigated in theory and experiment. The gain competition between signal and amplified spontaneous emission is theoretically investigated based on the absorption and emission characteristics of Yb3+. Available approaches to suppress parasitic oscillation are analyzed. In experiments, 1018, 980, 1173 nm fiber lasers are established, and the maximum output power of the three fiber lasers are 309, 1.05, 15.7 W, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 902008 (2013)
Tunable Single Longitudinal Mode Nd:YAG Green Laser
Zhang Junxuan, Li Feng, Bi Decang, and Zhu Xiaolei
A laser diode dual-end pumped injection-seeded Nd:YAG green laser is designed. By the reasonable design of the cavity structure parameters, the fundamental transverse mode laser is obtained because of the good match between the gain medium activation area and the fundamental transverse mode volume. In 48 hours of contiA laser diode dual-end pumped injection-seeded Nd:YAG green laser is designed. By the reasonable design of the cavity structure parameters, the fundamental transverse mode laser is obtained because of the good match between the gain medium activation area and the fundamental transverse mode volume. In 48 hours of continuous work, the output laser which keeps good single frequency and energy fluctuation is less than 2.9%. In conductively cooled structure, the high beam quality, high repetition frequency, narrow pulse width and tunable 532 nm single-frequency green laser is implemented. The repetition frequency of the laser is 1kHz. The output energy is more than 4 mJ, and the pulse width is around 6.5 ns. The beam quality M2 of 1.166 in the horizontal direction and 1.158 in the vertical direction is detected. The output green laser with continuous tuning range of 15 GHz is achieved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 902009 (2013)
Simulation of Excimer Laser Based on Zemax Software
Jin Yuhua, Zhao Yan, and Jiang Yijian
A method to simulate the energy distribution of excimer laser is provided. The color image of an actual excimer laser energy distribution is captured, and the image and extract relevant information are analyzed using Matlab software. Meanwhile the actual excimer laser light source is simulated by the optical software ZA method to simulate the energy distribution of excimer laser is provided. The color image of an actual excimer laser energy distribution is captured, and the image and extract relevant information are analyzed using Matlab software. Meanwhile the actual excimer laser light source is simulated by the optical software Zemax. The beam dimension of the actual excimer laser light source is about 16.5 mm×35.4 mm. The beam divergence is about 3.3 mrad in the x direction, and 11.5 mrad in the y direction. The beam dimension of the light source simulated by this method is about 16.7 mm×35.3 mm, and the beam divergence is about 3.41 mrad in the x direction, and 11.53 mrad in the y direction. The energy distribution of the simulated light is consistent with that of the actual excimer laser light in details. This method provides a perfect solution to the optical simulation difficulty of the complex spatial energy distribution of the excimer laser. It also provides a technical foundation for the investigation on the optical property of excimer laser and development of its optical components..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 902010 (2013)
Materials and Thin Films
Near-Infrared Spectroscopic Properties and Energy Transfer Mechanism of Er3+/Tm3+-Codoped TeO2-ZnO-Na2O Glasses
Yin Dandan, Zhou Yaxun, Zheng Shichao, Xu Xingchen, Wang Xunsi, and Dai Shixun
A series of Er3+/Tm3+ codoped tellurite glasses are prepared using the high-temperature melt-quenching method and the 1.85 μm band infrared spectroscopic properties of Tm3+ under the 800 nm LD excitation are investigated by measuring the differential scanning calorimeter (DSC) curves, absorption spectra, fluorescence sA series of Er3+/Tm3+ codoped tellurite glasses are prepared using the high-temperature melt-quenching method and the 1.85 μm band infrared spectroscopic properties of Tm3+ under the 800 nm LD excitation are investigated by measuring the differential scanning calorimeter (DSC) curves, absorption spectra, fluorescence spectra and fluorescence decay curves of glass samples, together with the calculations of the Judd-Ofelt intensity parameters, spontaneous radiative transition rates and radiative lifetimes of Tm3+ ions. The results show that the Er3+/Tm3+ codoped tellurite glasses have good thermal stability and the 1.53 μm band fluorescence intensity of Er3+ ions decreases rapidly, while the 1.85 μm band fluorescence intensity of Tm3+ ions increases accordingly with the increase of Tm3+ ion doping concentration. The analysis of 1.85 μm band luminescence processes indicates that the improvement of the infrared fluorescence intensity of Tm3+ can be attributed to the comprehensive energy transfers of Tm3+3H4→Er3+4I9/2, Er3+4I11/2→Tm3+3H5, and Er3+4I13/2→Tm3+3F4, and the micro-parameters, critical radius and phonon contribution for the above energy transfer processes are calculated and analyzed further. The research demonstrates that the Er3+/Tm3+ codoped tellurite glass is a promising host material applied for the 1.85 μm band fiber lasers..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 906001 (2013)
650 nm Visible Band Thermo-Optic Switch Based on Bonded Organic-Inorganic Hybrid Materials
Zhang Haixin, Wang Lei, Niu Xiaoyan, Sun Xiaoqiang, Wang Fei, Cheng Changming, and Zhang Daming
We propose and design a kind of 650 nm band all organic-inorganic hybrid material embedded Mach-Zehnder (MZ) thermo-optic switch. The main parameters of the thermo-optic switch are optimized, and theoretical transmission simulations of this device are carried out by COMSOL and Rsoft. The material is synthesized in our We propose and design a kind of 650 nm band all organic-inorganic hybrid material embedded Mach-Zehnder (MZ) thermo-optic switch. The main parameters of the thermo-optic switch are optimized, and theoretical transmission simulations of this device are carried out by COMSOL and Rsoft. The material is synthesized in our laboratory. The thermal stability of the material has been greatly improved, since the body of this material is a rigid inorganic backbone of Si-O-Ti chains, and the material has a higher thermo-optic coefficient. By altering the refractive index through changing the Ti cotent in the material, we get the core and clab materials respectively. The material has good film characteristic and workability, which make the production process simple. The device is low loss, and has potential sensing applications. The thermo-optic switch is tested and we get a good near-field output spot. The insertion loss of the device is 6.5 dB, the propagation loss is 0.85 dB/cm, the rise response time is 190 μs and the fall response time is 350 μs, the extinction ratio is 8.5 dB. The thermo-optic switch has broad application prospects in plastic optical fiber transmission system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 906002 (2013)
Realization of Antireflection Coatings for 193 nm P-Polarized Light at Large Angle
Li Chun, Jin Chunshui, Jin Jingcheng, and Chang Yanhe
The substrate and layer materials used for the antireflection coatings at 193 nm range are calculated and analyzed, and the deposition technique and parameters are carefully chosen and optimized. Based on these analyses the antireflection coatings for 193 nm light at large incident angle are designed, fabricated and teThe substrate and layer materials used for the antireflection coatings at 193 nm range are calculated and analyzed, and the deposition technique and parameters are carefully chosen and optimized. Based on these analyses the antireflection coatings for 193 nm light at large incident angle are designed, fabricated and tested. The results show that after coating, the residual reflection is lower than 1% and the single transmission of the coating is higher than 96% when the incident angle is 68°~72°. The single round trip energy loss of the linewidth narrowing module is calculated before coating and after coating, which confirms the necessity of this antireflection coating..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 907001 (2013)
Study of Protective Layer for 2.4 m Telescope′s Al Coating
Lun Baoli, Qin Songnian, Wang Jianguo, and Liu Zhong
The technology for coating protective dielectric layer to 2.4 m telescope′s aluminium coating is studied using the large vacuum evaporation coating machine ZZS3200, which is the first vacuum evaporation chamber evaporating materials from top to bottom in China. According to the profile of 2.4 m telescope′s primary mirrThe technology for coating protective dielectric layer to 2.4 m telescope′s aluminium coating is studied using the large vacuum evaporation coating machine ZZS3200, which is the first vacuum evaporation chamber evaporating materials from top to bottom in China. According to the profile of 2.4 m telescope′s primary mirror and the geometry of ZZS3200, the uniformity of the dielectric layers is analyzed and a moly boat source for evaporating materials from top to bottom is designed. The result shows that the index of evaporation characteristics is approximate to 1, and the non-uniformity of the dielectric film on 2.4 m mirror is less than 13.6%. Comparing the effect of removing the old protected aluminium coating, it is found that, compared with the SiO2-protected coating, MgF2-protected coating is easier to be removed, which can decrease the erosion of mirror during the coating removal, and has higher speculum reflectivity. The 2.4 m telescope′s mirror aluminium coating with MgF2-protected layer is completed. The reflectivity of witness sample is 87.16％ in the wavelength range of 350～1100 nm, and the limiting magnitude is not less than 23.5 magnitude..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 907002 (2013)
Design and Fabrication of Near Space Laser Communication Link Optical System Filter Film
Fu Xiuhua, Mo Zhaoyan, Huang Jinlong, Mo Shuhui, and Wu Boqi
In order to improve the signal-to-noise ratio of the near space laser communication and avoid interference from stray light, we often use filters to filter and collect the signal. According to the parameter requirements of filters in the communication system, we select appropriate film materials with the preparation teIn order to improve the signal-to-noise ratio of the near space laser communication and avoid interference from stray light, we often use filters to filter and collect the signal. According to the parameter requirements of filters in the communication system, we select appropriate film materials with the preparation technology to design the film system. Electron beam heating evaporation and ion-assisted deposition system are adopted for film preparation. Using the film system′s evaluation function and the mathematical model related to the film sensitivity, the sensitivity of the film is optimized. The filters meet the requirements of the use of near space laser communication link optical system, and pass the environmental testing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 907003 (2013)
Measurement and Metrology
Far-Field Multi-Parameter Measurement of Diffractive Optical Element for Pupil Shaping in Lithography System
Hu Zhonghua, Zhu Jing, Yang Baoxi, Pen Xuefeng, Zeng Aijun, and Huang Huijie
Diffractive optical element (DOE) is widely used to generate various illumination modes for pupil shaping in the lithography system. A far-field multi-parameter measuring method for the DOE is proposed according to its testing requirements of optical performance. The multi-parameters of optical performance, such as theDiffractive optical element (DOE) is widely used to generate various illumination modes for pupil shaping in the lithography system. A far-field multi-parameter measuring method for the DOE is proposed according to its testing requirements of optical performance. The multi-parameters of optical performance, such as the pole balance, the pole opening angle, the pole azimuth angle, the semi-aperture angle, and the radial intensity distribution are obtained simultaneously by converting the far-field intensity distribution. The multi-parameter measurement and analysis of DOE made abroad are done experimentally. And the experimental results indicate that this measuring method can be applied to the testing of DOE for pupil shaping in the lithography system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 908001 (2013)
Measurement for Retardation of Wave Plates Using the Relative Angle Method
Gu Yaohui, Zhang Yan, Jiao Xiang, and Zhu Jianqiang
A relative angle method for measuring the phase retardation of wave plates is presented. Although it′s difficult to accurately determine the extinction position, this method has nothing to do with it. Compared with traditional methods, there is no need to find the extreme value positions to adjust the azimuth angle of A relative angle method for measuring the phase retardation of wave plates is presented. Although it′s difficult to accurately determine the extinction position, this method has nothing to do with it. Compared with traditional methods, there is no need to find the extreme value positions to adjust the azimuth angle of the optical elements. And it can eliminate the influence of positioning error on the measurement results. This method not only reduces the difficulty of measurement, but also improves the accuracy of the measurement. Based on Mueller matrix, the theory as well as the measurement formula is derived. The phase retardation of 1/4 plate is measured when the suitable wavelength is 532 nm. The mean value and standard deviation are 90.072° and 0.42°,respectively. The usefulness of this method is verified by the result of the experiment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 908002 (2013)
Analysis of Dynamic Allan Variance for Fiber Optic Gyro under Vibration and Variable Temperature Conditions
Li Jichen, Gao Fengqi, Wang Guanglong, Gao Weiwei, Zhu Wenjie, and Wang Ming
Allan variance method is an effective tool for the analysis of the fiber optic gyro (FOG) static noise, but it only applies to stationary signals and can′t reflect the dynamic characteristics of FOG. In order to comprehensively study on FOG random error, dynamic Allan variance (DAVAR) is used to analyse the high precisAllan variance method is an effective tool for the analysis of the fiber optic gyro (FOG) static noise, but it only applies to stationary signals and can′t reflect the dynamic characteristics of FOG. In order to comprehensively study on FOG random error, dynamic Allan variance (DAVAR) is used to analyse the high precision FOG. The mathematical foundations of the DAVAR are presented and discussed, and the measured data under vibration and variable temperature conditions are obtained respectively, and the noise of which is calculated through DAVAR, its effectiveness is shown by performing extensive numerical analyses on simulated and experimental data. Experimental results show that the DAVAR analysis method can not only determine the proportion of the various noise factors, but also identify and refine the FOG noise in mutation environment, and the Allan variances are visually reflected in a 3D graph. The results prove the validity and the effectiveness of the proposed new tool..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 908004 (2013)
Technology for Rapid Detection of Laser-Induced Damage on Optical Components Using Line-Scan Phase Differential Imaging
Fan Xingnuo, Jang Youen, and Li Xuechun
A technology for detecting laser-induced damage on optics, using line-scan imaging and dark-field image principle, is proposed. According to the phase differential theory, this technology only responds to laser-induced damages which cause the phase change, and thus the detected images have high contrast. In order to unA technology for detecting laser-induced damage on optics, using line-scan imaging and dark-field image principle, is proposed. According to the phase differential theory, this technology only responds to laser-induced damages which cause the phase change, and thus the detected images have high contrast. In order to understand the features of the technology, the principle of the technology is analyzed, and the characteristics of the detection technology are verified by experiment. Experimental studies reveal that the technology can acquire high contrast and high-resolution laser-induced damage image, and that it has the potential to quickly detect the laser-induced damage of large aperture optical components..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 908005 (2013)
Simulation Research on the Light-Scattering Properties of the Subsurface Damage of Optical Components
Tian Ailing, Wang Hui, and Wang Chunhui
There is a serious effect directly for optical element sub-surface damage to optical performance and laser damage threshold in the application, and the primary cause is due to light scattered by subsurface damage. Aim to K9 glass optical element, the simulation model is built. By using finite difference time domain (FDThere is a serious effect directly for optical element sub-surface damage to optical performance and laser damage threshold in the application, and the primary cause is due to light scattered by subsurface damage. Aim to K9 glass optical element, the simulation model is built. By using finite difference time domain (FDTD) method, the light field distributions, which are the incident light modulated by subsurface micro-cracks and bubbles, are simulated, and the scattering light intensity variation received by detector is analyzed. The results have important theoretical guideline to further study the measuring methods of optical components subsurface damage..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 908006 (2013)
Apparatus Design for Surveying Relative Angular Translation of Airborne Optoelectronic Platform
Wang Zichen, Dai Ming, Li Gang, Wang Yongyang, Song Yueming, and Gao Yujun
In order to resolve the problem of target orientation precision descent that is caused by relative angular translation between optoelectronic (OE) platform and aircraft, a measurement system is proposed to survey this angular movement. The reason of target orientation descent of present airborne OE platform is analyzedIn order to resolve the problem of target orientation precision descent that is caused by relative angular translation between optoelectronic (OE) platform and aircraft, a measurement system is proposed to survey this angular movement. The reason of target orientation descent of present airborne OE platform is analyzed and both attitude measurement and camera calibration algorithm based on multiple control points on system are involved. Primary reason which conducts target orientation descent is introduced. Using monocular vision, angular translation measurement method is proposed, and mathematical model is set up based on camera calibration. Then, three-step method used for surveying relative angular translation is established by stochastic parallel gradient descent (SPGD) and direct linear transformation (DLT) with multiple control points. Both simulative and experimental results are achieved. The experiments show that the precision of measuring relative angular translation method is smaller than 0.092° and 0.54 ms is consumed by a single measurement. It can satisfy the requirements of relative angular translation between aircraft and OE platform precisely and timely..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 908007 (2013)
Optical Communication
Phase Demodulation Technology Using a Multi-Frequency Source for Discrimination of Interference-Fading Induced False Alarms in a φ-OTDR System
Zhou Jun, Pan Zhengqing, Ye Qing, Cai Haiwen, Zhao Hao, Qu Ronghui, and Fang Zujie
The characteristics of interference fading in the phase-demodulated phase-sensitive optical time domain reflectometer(φ-OTDR) system are investigated. It is found that the fading waveforms have high similarity for different pulse scans, but obvious differences for different optical frequencies. An improved model for raThe characteristics of interference fading in the phase-demodulated phase-sensitive optical time domain reflectometer(φ-OTDR) system are investigated. It is found that the fading waveforms have high similarity for different pulse scans, but obvious differences for different optical frequencies. An improved model for randomness and coherent noise of Rayleigh scattering is presented. It can be concluded that the composite Rayleigh scattering coefficient is a function of laser frequency and the index distribution, which could explain the experimental results reasonably. In order to eliminate the false alarms due to interference fading, a multi-frequency method is proposed, which can improve the accuracy of the phase demodulation in the φ-OTDR system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 905003 (2013)
Phase-Shifted Fiber Bragg Grating Strain Sensor Demodulated by Edge Filter
Ma Weichao, Chen Shaohua, Zhao Kun, and Wang Aijun
A novel strain sensor based on phase-shifted fiber Bragg grating (PSFBG) is designed. A PSFBG and a fiber Bragg grating (FBG) are connected together by an optical circulator, and symmetrically pasted on the uniform strength cantilever beam along the median. Both of them are the main sensing component of the strain probA novel strain sensor based on phase-shifted fiber Bragg grating (PSFBG) is designed. A PSFBG and a fiber Bragg grating (FBG) are connected together by an optical circulator, and symmetrically pasted on the uniform strength cantilever beam along the median. Both of them are the main sensing component of the strain probe. Because the location is next to the median, they have the same strain, and create sensing light which carries information and has extremely narrow line-width. Finally, the strain can be demodulated by an edge filter. The sensing light is got by theoretical simulation, and in experiment its line-width is only 101 pm. The experimental results are in good agreement with numerical simulation. In the experimental verification of strain sensor, the demodulation results have a good linear relationship with the signal to be measured. The fitting goodness is 0.994, and the resolution of strain probe is 1.5 με. The strain sensor based on this design is of high resolution and low cost, and is not chirped. It has a good practical value..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 905004 (2013)
Research of Sampling and Propagating Characteristics of High Power Ultraviolet Nanosecond Laser Pulse
Tang Qing, Yang Lin, Guo Yajing, Ouyang Xiaoping, Tang Shunxing, and Zhu Baoqiang
In order to lower the costs, and reduce the use of devices such as osillograph and fast response photodiode in SG Ⅱ, the ultraviolet optical fiber is used to sample and integrate measurement for the high power ultraviolet nanosecond laser pulse. Through the theoretical analysis and simulation study of the propagate chaIn order to lower the costs, and reduce the use of devices such as osillograph and fast response photodiode in SG Ⅱ, the ultraviolet optical fiber is used to sample and integrate measurement for the high power ultraviolet nanosecond laser pulse. Through the theoretical analysis and simulation study of the propagate characteristics and the condition of distortionless propagation of the high power ultraviolet nanosecond laser pulse in the optical fiber, different core diameter fibers are chosen to carry on the experimental research. It shows that the distortion is low when the high power ultraviolet nanosecond laser pulse propagates in the 25 μm core diameter fiber. The 25 μm core diameter optical fiber is suitable for long distance propagation and is a preferable medium for fiber sampling and propagating. A demonstrative experiment is taken to prove the feasibility of integrate measurement. These results provide theoretical and experimental basis for the high power laser pulse integration measurement of SG Ⅱ..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 905006 (2013)
Rapid Communications
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Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 9060001 (2013)
Geometric Optics
Effect of Fiber Length on Distance Measurement Based on Optoelectronic Oscillator
Zhang Tao, Zhu Jigui, Guo Tinghang, and Ye Shenghua
The extra-long optical cavity of optoelectronic oscillator (OEO) and the relationship between oscillation frequency shift and the variation of cavity length open the possibility for high-accuracy distance measurements at long range. Optical fiber not only affects the spectrum purity of the output microwave, but also deThe extra-long optical cavity of optoelectronic oscillator (OEO) and the relationship between oscillation frequency shift and the variation of cavity length open the possibility for high-accuracy distance measurements at long range. Optical fiber not only affects the spectrum purity of the output microwave, but also determines the sensitivity of distance measurement. Based on the theory of optoelectronic oscillator and the distance measurement method, the effects of optical fiber length on spectral purity of OEO and measurement sensitivity are analyzed respectively. Fiber loops with different lengths are used in experiments in order to verify the results of analysis. Considering the demands of the measurement sensitivity, the spectral purity and the measurement range, as well as the error introduced by the environment, the fiber length of OEO will be about 1 km when the resolution of frequency measurement is 1 Hz..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 908003 (2013)
Optical Design and Fabrication
Study on a Novel Depolarizer Whose Optical Axes are Fan-Shaped Distribution
Ren Shufeng, and Wu Fuquan
A novel birefringent depolarizer whose optical axes are fan-shaped distribution is designed. Using the idea of superposition of transmitted light, the depolarization performance for linearly polarized light is studied. And the formula of degree of depolarization (D) is obtained. The theory shows that D changes periodicA novel birefringent depolarizer whose optical axes are fan-shaped distribution is designed. Using the idea of superposition of transmitted light, the depolarization performance for linearly polarized light is studied. And the formula of degree of depolarization (D) is obtained. The theory shows that D changes periodically with the vibration azimuth angle (VAA) of incident light and optical path difference (OPD) on the basis of large enough wedge angle. D is 100% when VAA takes (N/2)π (N is integer), independent of the OPD. And D is the worst when VAA takes (2N+1)π/4. Adjusting the incident angle is adopted to improve D. The experiment results accord with the theory. And the D value of sample is over 98.84% for any VAA when the incident angle is 4°. So the design is feasible and the research method is so simple and clear that it can provide a new reference for the study of depolarizer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 916001 (2013)
Fast and Accurate Laser Beam Automatic Alignment System Based on CMOS Sensor
Li Yao, Wang Ding, Guo Xiaoyang, and Leng Yuxin
A new system is developed to adaptively collimate laser beam direction, with high speed and high accuracy. The sensing module of this system consists of an optical layout using pinhole to amplify the beam drift and a complementary metal-oxide-semiconductor transistor sensor. An field programmable gate array chip is theA new system is developed to adaptively collimate laser beam direction, with high speed and high accuracy. The sensing module of this system consists of an optical layout using pinhole to amplify the beam drift and a complementary metal-oxide-semiconductor transistor sensor. An field programmable gate array chip is the core of the signal processing module to perform high speed calculation and feedback control. At the aspect of software, an algorithm is designed to derive the driving signal for automatic alignment, which is capable of uncoupling the horizontal and vertical adjustment and suitable for highly accurate automatic control. Experiments are conducted to test the performance of the system. Results show that, the system implements feedback control with accuracy of 2.5 μm and the feedback frequency about 1 kHz, and can obviously reduce the beam drifting with the frequency below 1 kHz..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 916002 (2013)
Optical Design of Space-Based Ultraviolet Tracking and Detailed Reconnaissance System
Li Bo, Wang Shurong, and Wang Junbo
A tracking and detailed reconnaissance system is designed for space-based ultraviolet (UV) tracking requirement. The system consists of two parts, tracking camera and detailed reconnaissance camera. Dual field of view and dual angular resolution are achieved by combining telescope system and relay lens. The telescope sA tracking and detailed reconnaissance system is designed for space-based ultraviolet (UV) tracking requirement. The system consists of two parts, tracking camera and detailed reconnaissance camera. Dual field of view and dual angular resolution are achieved by combining telescope system and relay lens. The telescope system is Mangin-Cassegrain structure, with diameter of 100 mm, focal length of 605 mm. For the tracking camera, the wavelength range is 250~400 nm, the field of view is 2.5°×1.9°, and the angular resolution is better than 180 μrad. For the detailed reconnaissance camera, the wavelength range is 200~360 nm, the field of view is 0.15°×0.11°, and the angular resolution is better than 13 μrad. The modulation transfer function (MTF) of tracking camera is better than 0.9, and the MTF of detailed reconnaissance camera is better than 0.8. The results meet the requirements of specifications through the design and optical software analysis..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 916003 (2013)
Remote Sensing and Sensors
A Method of Classification for Airborne Full Waveform LiDAR Data Based on Random Forest
Fan Shijun, Zhang Aiwu, Hu Shaoxin, and Sun Weidong
Aiming at airborne full waveform data classification, the paper proposes a random forest method based on point cloud classification algorithm. The amplitude of the fullwaveform echo and echo times, as well as the echo width are extracted. Extract and select the features using the method proposed in this paper to build Aiming at airborne full waveform data classification, the paper proposes a random forest method based on point cloud classification algorithm. The amplitude of the fullwaveform echo and echo times, as well as the echo width are extracted. Extract and select the features using the method proposed in this paper to build a feature vector. Using the random forest method, the laser point clouds are divided into three types of vegetation, ground and building. By comparative analysis of random forests method and the support vector machine, the results present that the extracted features show good stability and efficiency, and the random forest classification method can achieve good classification effect in the urban classification applications..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 914001 (2013)
Spectroscopy
Fluorescence Rejection in Raman Testing of Illegal Food Additives
Zhou Hongwu, Cai Zhijian, and Wu Jianhong
A compact shifted excitation Raman difference spectroscopy (SERDS) multi-wavelength light source based on tunable external cavity semiconductor laser (ECDL) is designed. A wavelength tuning range of 15 nm can be achieved, with the laser spectral line-width less than 0.2 nm and output power up to 80 mW. We also developeA compact shifted excitation Raman difference spectroscopy (SERDS) multi-wavelength light source based on tunable external cavity semiconductor laser (ECDL) is designed. A wavelength tuning range of 15 nm can be achieved, with the laser spectral line-width less than 0.2 nm and output power up to 80 mW. We also developed a deconvolution algorithm with multiple constraints to process the difference spectrum of SERDS, which can suppress the noises efficiently. This SERDS system is used to test several illegal food additives (sudan I, rhodamine B, melamine, hexamine). The results show that this method can effectively remove the background fluorescent and significantly increase the signal-to-noise ratio of Raman detection..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 915001 (2013)
Study on Ratio Demodulation for Ammonia Concentration Measurement Based on THz-TDS
He Quanhua, Jia Dagong, Zhang Hongxia, Li Quan, Han Jiaguang, and Zhang Yimo
Terahertz time-domain spectroscopy (THz-TDS) technology has attracted enormous research interest in recent years due to its advantages of large dynamic range, high sensitivity and signal-noise rate (SNR), etc. However, the strong absorption of water vapor to terahertz wave has great impact on gas concentration demodulaTerahertz time-domain spectroscopy (THz-TDS) technology has attracted enormous research interest in recent years due to its advantages of large dynamic range, high sensitivity and signal-noise rate (SNR), etc. However, the strong absorption of water vapor to terahertz wave has great impact on gas concentration demodulation results. In this paper, a quantitative analysis of different concentrations of ammonia is conducted on using THz-TDS at room temperature and pressure with the presence of water vapor in the measurement system. We propose and demonstrate a ratio demodulation method for the ammonia concentration and it effectively reduces the influence of water vapor compared with the difference method and the humidity compensation method. The experimental results show that the detection sensitivity increases to 33.0 mg/m3 and the concentration retrieval error can be controlled within 48.2 mg/m3 when the interaction length between the gas and THz wave is 96 mm. The concentration retrieval error is reduced by 84.6% and 77.4% compared with the difference method and the humidity compensation method respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 40, Issue 9, 915002 (2013)
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