Journals >Chinese Journal of Lasers
Contents
2011
Volume: 38 Issue 9
43 Article(s)
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[in Chinese]
Research on Dual-Mode Hybrid Detection Technology Using Laser to Point Directed by Infrared Camera
Zhang Bingna, Zhang Liang, Huang Genghua, Shu Rong, and Wang Jianyu
With the development from scanning mode to staring mode, infrared radiation (IR) optoelectronic system can realize scouting in large field. But it can only get the two-dimensional information of target. If combined with laser active detection, three-dimensional information of angle-angle-distance can be got, which are With the development from scanning mode to staring mode, infrared radiation (IR) optoelectronic system can realize scouting in large field. But it can only get the two-dimensional information of target. If combined with laser active detection, three-dimensional information of angle-angle-distance can be got, which are mutually complementary. A laser active detection technology with pointed function based on two-dimensional piezoelectric fast-steering mirror (PFSM) is proposed and discussed, which realizes the IR imaging /ladar dual-mode detection to track the target with high precision. The field of view and its linearity are analyzed and tested, which accord well with the calculation result..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 917001 (2011)
Subpixel Location Algorithm for Laser Spot in Fish-Eye Imaging Laser Warning System
Dong Hongjun, Zhou Zhongliang, and Wang Long
The directional accuracy of threatening laser is highly dependent on the laser spot center location accuracy for the imaging laser warning system. The spot features of wide field-of-view fish-eye imaging laser warning system are analyzed. As the low fill factor of CMOS sensor and the energy distribution asymmetry of spThe directional accuracy of threatening laser is highly dependent on the laser spot center location accuracy for the imaging laser warning system. The spot features of wide field-of-view fish-eye imaging laser warning system are analyzed. As the low fill factor of CMOS sensor and the energy distribution asymmetry of spot in big incident angle region will affect the location accuracy of spot center, an improved algorithm is proposed. Firstly, it separates the two-dimensional Gaussian function integral of pixel intensity readings into a product of two one-dimensional integrals. Then the Gaussian function integrals which are difficult to solve even by numerical means are inverted using an error function approximation approach. Finally, the spot center coordinates are derived in terms of the intensity ratios of neighboring pixels. The accuracy and stability are verified and compared with traditional algorithm by experiment. The experimental results show that this method can reduce the location error caused by incomplete fill ratio of CMOS pixel and large unsymmetrical optical aberration of fish-eye lens. The spot positioning precision in paraxial region and big incident angle region are 1/80 and 1/70 pixel, respectively. The maximum error is less than 1/30 pixel. It can satisfy the system requirements of laser warning equipment, including real time, higher precision, as well as strong stabilization for spots in different areas of CMOS sensor..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 917002 (2011)
Laser Three-Dimensional Display System Based on Polarization Compensated Liquid Crystal on Silicon Optical Engine
Qi Yan, Bi Yong, Wang Yu, Wang Aibin, Wang Yanwei, Cheng Hua, Wang Bin, Fang Tao, Yan Boxia, and Zheng Guang
Laser three-dimensional (3D) display system based on polarization compensated liquid crystal on silicon (LCOS) optical engine compensates the polarization loss of the traditional LCOS optical engine, light of different polarizations entering into the optical engine is utilized in the process of the imaging process, eacLaser three-dimensional (3D) display system based on polarization compensated liquid crystal on silicon (LCOS) optical engine compensates the polarization loss of the traditional LCOS optical engine, light of different polarizations entering into the optical engine is utilized in the process of the imaging process, each polarization is directed to one of two LCOS panels. In two-dimensional (2D) operation, the same image is presented on each LCOS, producing a double-brightness image. In 3D mode, one LCOS produces a right-eye image and the other produces a left-eye image. The images are optically combined and leave the projector through the same projection lens. This improved optical engine realizes 3D display，as well as enhances the efficiency of the optical engine when working in 2D display mode. This approach is highly efficient in that nearly 100% of the light emitted by the lasers utilized..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 917003 (2011)
Biomedical Photonics and Laser Medicine
Surface-Enhanced Raman Scattering Spectroscopic Assay of Immunohistochemically Stained Human Colon Cancer Tissue
Xi Gangqin, Chen Yanping, Chen Gang, Zheng Xiongwei, Feng Shangyuan, Yu Yun, Lin Xiaoqian, and Chen Rong
To explore the feasibility of surface-enhanced Raman scattering (SERS) labeled immunoassay technology for clinical analysis protein expression in colon cancer tissue sections, we develop 4-mercaptobenzoic acid (4-MBA) labeled Au/Ag core-shell nanoparticles (NPs) as assay platform for the detection of carcinoembryonic aTo explore the feasibility of surface-enhanced Raman scattering (SERS) labeled immunoassay technology for clinical analysis protein expression in colon cancer tissue sections, we develop 4-mercaptobenzoic acid (4-MBA) labeled Au/Ag core-shell nanoparticles (NPs) as assay platform for the detection of carcinoembryonic antigen (CEA) in colon cancer tissue samples. Firstly, Raman active molecule 4-MBA is adsorbed on Ag shell Au core bimetallic NPs, and then the SERS-tagged nanoprobes are modified with CEA monoclonal antibody, forming CEA-SERS probes. Finally, according to the theory of specific binding of SERS-tagged antibody and the corresponding antigen, SERS spectra and imaging are performed in tissue sections after dropping the SERS-tagged immuno-nanoprobes. Data show that colon cancer epithelium appears strong SERS signals, while stroma and normal epithelium do not appear SERS signals, except a few non-specific adsorption signals. As can be clearly seen from the SERS images, the colon cancer epithelium highly expresses CEA, while stroma and normal epithelium do not. In conclusion, due to high sensitivity and high specificity of SERS-tagged immuno-nanoprobes, the SERS labeled immunoassay technology is promising for the analysis of the protein expression in colon cancer tissue sections and has the potential to be developed into a significant aiding tool for pathological diagnosis of colon cancer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 904001 (2011)
Laser Manufacturing
Patterned Organic Semiconductor Poly (Vinylidene Fluoride) Surfaces Using KrF Excimer Laser Treatment
Liu Ying, and Jiang Yijian
We describe a novel procedure for fabricating conductive patterns on polyvinylidene fluoride (PVDF) substrates using KrF excimer laser treatment. Based on the etching defects which act active centre for conducting layer, the outline of the patterns formed by etching lines is created on PVDF surfaces via a 248 nm excimeWe describe a novel procedure for fabricating conductive patterns on polyvinylidene fluoride (PVDF) substrates using KrF excimer laser treatment. Based on the etching defects which act active centre for conducting layer, the outline of the patterns formed by etching lines is created on PVDF surfaces via a 248 nm excimer laser directwriting optical system; the semiconducting layer can be induced along the selective direction, so that various patterned conductive surface is obtained via 248 nm laser irradiation. The results show that the etching defects not only play the active centres but also effectively separate the conducting layer; using the mask to limit the area of laser irradiation so that it controls the outline of conducting layer. Formation mechanism for conducting layer is proposed by the SEM results at different positions of conducting layer along its spreading direction. The paper will be possible to provide guidance for the conducting PVDF based electronic devices, and patterning other conducting polymer by laser techniques..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 903001 (2011)
Effects of CO2 Laser Irradiation on Surface Morphology and Stress Distribution of Fused Silica
Li Xibin, Wang Haijun, Yuan Xiaodong, He Shaobo, Xiang Xia, Lü Haibing, and Zheng Wanguo
10.6 μm CO2 laser beams with different diameters are used to irradiate surface damage pits of fused silica. Experimental results show that a single pulse irradiation could repair damage pits below 50 μm efficiently, whose damage threshold could be recovered to the threshold of intact substrate. For damage with size bet10.6 μm CO2 laser beams with different diameters are used to irradiate surface damage pits of fused silica. Experimental results show that a single pulse irradiation could repair damage pits below 50 μm efficiently, whose damage threshold could be recovered to the threshold of intact substrate. For damage with size between 50 and 300 μm, deep cracks could be efficiently repaired by using long time irradiation with low power laser before melting. It shows that laser power, irradiation time, and especially beam diameter are the main factors influencing the thermal stress distribution. However, pre-irradiation is in favor of melting crack in deep damage. After irradiation by 351 nm, 6.3 ns NdYAG laser, experimental results show that when the repair region is on the input surface, annular raised damaged region forms because of laser modulation. When the repair region is on the output surface, ablation is the main causation influencing the threshold advancement..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 903002 (2011)
Research of Al2O3+13%TiO2 Ceramic Nanoparticles Growth during Laser Cladding Process Based on Brook′s Theory
Wang Dongsheng, Tian Zongjun, Wang Jingwen, Duan Zongyin, Shen Lida, and Huang Yinhui
In order to optimize the processing parameters of nanostructured coating during laser cladding, the changes of nanoparticles size under high energy density laser are investigated. Based on the Brook′s classical theory about grain growth and temperature field of laser cladding with finite element software Ansys, the nanIn order to optimize the processing parameters of nanostructured coating during laser cladding, the changes of nanoparticles size under high energy density laser are investigated. Based on the Brook′s classical theory about grain growth and temperature field of laser cladding with finite element software Ansys, the nanoparticles growth of laser-clad nanostructured Al2O3+13%TiO2 (mass fraction) coating prepared by plasma spraying are investigated. The effects of nanoparticles original size and laser-cladding region on grain growth are studied. Meanwhile, experiment of laser cladding on nanostructured Al2O3+13%TiO2 prepared by plasma spraying is carried out. The results show that the experimental overall trend of nanoparticles growth is consistent with the calculated result during laser cladding process, which indicates that the nanoparticles growth theory based on Brook′s theory is correct and reliable. The theory provides theoretical basis for nanoparticles growth during laser cladding process..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 903003 (2011)
Fabrication of Microfluidic Chip with Two-Step Using Excimer Laser Ablation Micromachining Technique and Replica Molding Technology
Shen Xuefei, Chen Tao, and Wu Jingxuan
We present an effective and low-cost method for fabricating microfluidic chip based on excimer laser direct-writing ablation and replica molding. It is based on a newly excimer laser micromachining technique that can accurately machine microfluidic chip microstructure with smooth surface profile. Microfluidic chips witWe present an effective and low-cost method for fabricating microfluidic chip based on excimer laser direct-writing ablation and replica molding. It is based on a newly excimer laser micromachining technique that can accurately machine microfluidic chip microstructure with smooth surface profile. Microfluidic chips with precise and smooth surface profiles are ablated by direct laser machining on an epoxy glue layer sticking on glass substrates. Laser-machined microfluidic chips are replicated by electroforming to obtain inverse metal molds. Finally, polycarbonate (PC) microfluidic chips are replicated from these metal molds using injection molding method. The relation between the process parameters (the translational speed of working platform and the laser fluence) and the micromachining quality (the depth and surface of the microchannel) is investigated. The profile accuracy and surface roughness of the produced microfluidic chip at each stage are measured and monitored. The average upper surface profile accuracy is better than 2 μm and the average surface roughness is less than 20 nm. Experimental data show the controllability and accuracy of this micromachining process. Experimental investigation is performed on the flow characteristics of water in two different roughness rectangle microchannels. The flow characteristics of water in the microchannels fabricated with the proposed combination method are better than those in the microchannels fabricated with laser direct-writing when the flow velocity is small..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 903004 (2011)
Laser Power Attenuation by Powder Flow in Coaxial Laser Cladding
Jin Shaowei, He Xiuli, Wu Yang, Ning Weijian, and Yu Gang
The laser power attenuation by powder flow in coaxial laser cladding is investigated numerically and experimentally. A steady model of powder concentration distribution is developed, considering the effect of substrate on gas-flow and rebound of powder particles. The relationship between powder concentration and attenuThe laser power attenuation by powder flow in coaxial laser cladding is investigated numerically and experimentally. A steady model of powder concentration distribution is developed, considering the effect of substrate on gas-flow and rebound of powder particles. The relationship between powder concentration and attenuation of laser power is analyzed. The effects of melt pool size and powder flow rate on a top hat laser beam attenuation are investigated. Results indicate that power attenuation by powder flow with the effect of substrate can be twice more than that without substrate. The attenuation is proportional to the powder flow rate and decreases with the increase of melt pool size when the pool size is small..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 903005 (2011)
Effects of Different Stress Ratios on Fatigue Crack Growth in Laser Shot Peened 6061-T6 Aluminum Alloy
Zhou Jianzhong, Xu Zengchuang, Huang Shu, Yang Xiaodong, Wang Chengdong, Yang Jing, Zuo Lidang, and Ji Xinglu
In order to investigate the effect of laser shot peening (LSP) on fatigue crack propagation of 6061-T6 aluminum alloy under different stress ratios, finite element software ABAQUS and fatigue analysis software MSC.Fatigue are used to establish the prediction model to analyze the effects of different stress ratios (R=0.In order to investigate the effect of laser shot peening (LSP) on fatigue crack propagation of 6061-T6 aluminum alloy under different stress ratios, finite element software ABAQUS and fatigue analysis software MSC.Fatigue are used to establish the prediction model to analyze the effects of different stress ratios (R=0.1, 0.3, 0.5) on crack propagation induced by LSP. The effects of residual compressive stress on the crack closure under different stress ratios are studied and the increase of fatigue life is predicted. The results show that fatigue crack growth rate decreases after LSP, compared with the untreated sample under three stress ratios. The value of stress ratio significantly affects the fatigue life of compact tension (CT) specimen after laser shot peening, however, the lower value of stress ratio is, the more the increase in fatigue life attained by LSP is..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 903006 (2011)
Elevated Temperature Tribological Behaviors of Laser Cladding NickelBased Composite Coating on Austenitic Stainless Steel,
He Xiangming, Liu Xiubo, Yang Maosheng, Shi Shihong, Wang Mingdi, and Fu Geyan
Aiming at improving hightemperature wear resistance of austenitic stainless steel, a wear resistant composite coating reinforced with hard (Cr,Fe)7C3 carbide and toughened by ductile γ(Ni,Fe) solid solution matrix is fabricated by a novel central hollow laser cladding technique. Sliding wear tests of the composite coAiming at improving hightemperature wear resistance of austenitic stainless steel, a wear resistant composite coating reinforced with hard (Cr,Fe)7C3 carbide and toughened by ductile γ(Ni,Fe) solid solution matrix is fabricated by a novel central hollow laser cladding technique. Sliding wear tests of the composite coating and substrate are conducted at ambient temperature, 300 ℃ and 600 ℃, respectively, and the corresponding wear mechanisms are discussed. Results indicate that the composite coating exhibits superior wear resistance than substrate either at ambient or high temperatures. At ambient temperature， the wear mechanism of the substrate is dominated by adhesive wear while the coating shows abrasive. At 300 ℃, the substrate′s wear mechanism is the combination of adhesive and abrasive wear while the coating′s is abrasive wear. As temperature attains 600 ℃, brittle fracture, plastic deformation and severe oxidation are discovered on the substate′s worn surface, while the coating exhibits mild adhesive and abrasive wear. The coating shows better sliding wear resistance at 600 ℃ than that at 300 ℃ owing to polishing effect and formation of lubricative continuous transfer films, which implies that it has large potential in higher temperatures..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 903007 (2011)
Laser Physics
50 W Class Double-End-Pumped Nd∶YVO4 TEM00 Mode Solid State Laser Oscillator
Zhao Zhigang, Dong Yantao, Pan Sunqiang, Liu Chong, Xiang Zhen, and Chen Jun
A 50 W class, high power 808 nm laser diodes double-end-pumped Nd∶YVO4 composite crystal laser oscillator is reported. The adoption of double-end-pumping configuration and composite crystal can effectively alleviate thermal effect and achieve more uniform thermal and gain distributions in the laser crystal. AsymmetricaA 50 W class, high power 808 nm laser diodes double-end-pumped Nd∶YVO4 composite crystal laser oscillator is reported. The adoption of double-end-pumping configuration and composite crystal can effectively alleviate thermal effect and achieve more uniform thermal and gain distributions in the laser crystal. Asymmetrical plane-plane dynamically stable resonator is employed, which can make the two stable zones separated. Making the laser operated in stable zone I, we can pump the laser crystal with high pump power and get very small misalignment sensitivity, which are favorable for high power output and resonator’s mechanical stability. After optimizing the length of the two cavity arms, we obtain 51.2 W continuous-wave (CW) TEM00 mode laser output with about 104 W pump power, corresponding to an optical-to-optical efficiency of 49.2%. With an acousto-optic (AO) Q-switch inserted into the resonator, pulsed laser can be obtained within the pulse repetition rate range of 50～600 kHz. Within the pulse repetition rate range of 100～600 kHz, the average output power is stable at 49 W and the pulse width changes from 18.2 ns to 85 ns. At a pulse repetition rate of 50 kHz, the average output power reduces to 43.2 W with pulse width of 13.5 ns and peak power of 64 kW..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 902001 (2011)
High-Power Vertical-Cavity Surface-Emitting Laser with AlN Film Passivation Layer
Zhong Gang, Hou Lifeng, and Wang Xiaoman
Self-heating in high-power vertical-cavity surface-emitting lasers (VCSELs) is an important influence factor for device characteristics. In order to improve device heat dissipation, a 980 nm high-power VCSEL on AlN film passivation layer is fabricated. The analog simulation and analysis on the high-power VCSEL show thaSelf-heating in high-power vertical-cavity surface-emitting lasers (VCSELs) is an important influence factor for device characteristics. In order to improve device heat dissipation, a 980 nm high-power VCSEL on AlN film passivation layer is fabricated. The analog simulation and analysis on the high-power VCSEL show that the AlN film passivation layer can improve the temperature distribution inside high-power VCSEL, reduce the thermal resistance of VCSEL and enhance the ability of heat dissipation. The AlN film passivation layer and the SiO2 film passivation layer high power VCSELs both with 200 μm aperture have been made by the same processes on the same epitaxial wafer. The two kinds of high power VCSELs have been tested comparatively, and the testing results show that the output power of the VCSEL on AlN film passivation layer is 470 mW at room temperature, which is 140 mW higher than that of the device on the SiO2 film passivation layer. It can operate at higher temperature up to 80 ℃ and has much better temperature and opto-electric characteristics..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 902002 (2011)
Diffraction Characteristic Analysis of Sinc-Apodized Reflective Volume Bragg Grating
Shen Benjian, Zheng Guangwei, Tan Jichun, and He Yanlan
It is an effective approach to obtain high power laser output by spectral beam combining technology based on the sinc-apodized reflective volume Bragg grating. Considering the polarization of the monochromatic plane wave incident beam, the effects of the grating parameters on the diffraction efficiency, spectral selectIt is an effective approach to obtain high power laser output by spectral beam combining technology based on the sinc-apodized reflective volume Bragg grating. Considering the polarization of the monochromatic plane wave incident beam, the effects of the grating parameters on the diffraction efficiency, spectral selectivity and angular selectivity of the grating are analyzed by using the chain matrix method. The results show that the incident angle affects the diffraction efficiency greatly when the incident beams have different polarizations. The diffraction efficiency of the sinc-apodized reflective volume Bragg grating increases with the increase of the grating thickness and/or refractive index modulation, and it can be achieved higher than 99% with different polarizations at small incident angle when the product of the grating thickness and refractive index modulation is larger than 1.7028×10-6. The spectral selectivity and angular selectivity of the sinc-apodized reflective volume Bragg grating increase with the increase of the refractive index modulation, but decrease with the increase of the diffraction efficiency. By optimizing the grating parameters of the sinc-apodized reflective volume Bragg grating, the channel spectral separation lower than 200 pm can be achieved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 902003 (2011)
Optimization Research of Temperature Controlling Performance for Green LD End-Pumped Solid-State Laser
Shen Yuan, and Deng Qilin
Design process of green laser diode (LD) end-pumped solid-state laser, finite element method (FEM) is applied for the optimization of temperature controlling performance. Using ANSYS, a finite element analysis software, we do thermal analysis of the temperature controlling structure by steady-state thermal simulation aDesign process of green laser diode (LD) end-pumped solid-state laser, finite element method (FEM) is applied for the optimization of temperature controlling performance. Using ANSYS, a finite element analysis software, we do thermal analysis of the temperature controlling structure by steady-state thermal simulation and transient thermal simulation and optimize the structure on the basis of analytic result. The results show that with the cooling capacity in the same input, the temperature controlling capacity of the optimized temperature controlling structure arises approximately 10%, showing a significant improvement over the initial structure. An experimental setup on the basis of optimized structure is made and its temperature controlling capacity is tested. The error between the experimental data and ANSYS thermal simulation data is less than 5%. The results show that finite element analysis has a significant effect on improving the temperature controlling performance of green laser diode end-pumped solid state laser..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 902004 (2011)
Vectorial Non-Paraxial Propagation of Four-Petal Gaussian Beams through an Eccentric Circular Aperture
Zhang Liangjun, Zhang Junyong, Zhang Yanli, Chen Baosuan, Liu De′an, Zhu Jianqiang, and Lin Zunqi
Based on the vectorial Rayleigh-Sommerfeld diffraction integrals, the model for four-petal Gaussian beams propagating through an eccentric circular aperture is built. By choosing oblique optical axis as the reference optical axis and expanding the hard-edged circular aperture function as a finite sum of complex GaussiaBased on the vectorial Rayleigh-Sommerfeld diffraction integrals, the model for four-petal Gaussian beams propagating through an eccentric circular aperture is built. By choosing oblique optical axis as the reference optical axis and expanding the hard-edged circular aperture function as a finite sum of complex Gaussian functions, an analytical solution is performed. Furthermore, the detailed numerical calculation for the two-dimensional beams is presented. The simulation also shows that f parameters, beam order, location of aperture and truncation parameter affect the diffracted field, including location of center intensity and beam width. All these characteristics help us understand four-petal Gaussian beams propagation better..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 902005 (2011)
Thermal Reaction of High Power Semiconductor Laser with Voids in Solder Layer
Ding Xiaochen, Zhang Pu, Xiong Lingling, Ou Xiang, Li Xiaoning, Xu Zhongfeng, Wang Jingwei, and Liu Xingsheng
With the improvement of power, efficiency, reliability, manufacturability, and cost of high power semiconductor laser, many new applications are being enabled. Most of the semiconductor laser bars are packaged with the indium solder. However, some small voids are created during the packaging process, which will be gradWith the improvement of power, efficiency, reliability, manufacturability, and cost of high power semiconductor laser, many new applications are being enabled. Most of the semiconductor laser bars are packaged with the indium solder. However, some small voids are created during the packaging process, which will be gradually enlarged by the electromigration and electrothermal migration of the indium solder. Voids may cause local overheating near the facets of the laser. Therefore it is necessary to study the thermal behavior of semiconductor laser bars with voids in the solder layer. The thermal behavior of a single-bar CS-packaged 40 W 808 nm semiconductor laser with voids in the solder layer is studied and the relationship between temperature and voids size is analysed. The distribution of voids is predicted according to the space spectrum of a 40 W 808 nm semiconductor laser bar and the simulation results. It is found that the simulation results agree well with the measurement of the scanning acoustic microscope (SAM) image of solder layer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 902006 (2011)
Structural Design of 808 nm InGaAlAs Vertical-Cavity Surface-Emitting Laser
[in Chinese]
A vertical-cavity surface-emitting laser (VCSEL) was structurally designed for emitting at 808 nm. Based on a comprehensive model, the composition and width of the compressively strained In1-x-yGaxAlyAs quantum well (QW) was determined. Using transmission matrix method, the spectral reflectance of distributed Bragg refA vertical-cavity surface-emitting laser (VCSEL) was structurally designed for emitting at 808 nm. Based on a comprehensive model, the composition and width of the compressively strained In1-x-yGaxAlyAs quantum well (QW) was determined. Using transmission matrix method, the spectral reflectance of distributed Bragg reflector (DBR) was plotted, and the pairs of the DBR were ascertained. The numerical simulation showed that the lasing wavelength of the In0.14Ga0.74Al0.12As/Al0.3Ga0.7As QW with the width of 6 nm is near 800 nm at room temperature. At the operating temperature, the material peak gain reaches 4000 cm-1. In addition, the designed Al0.9Ga0.1As/Al0.2Ga0.8As DBR is gradient, and the thickness of the gradient layer is 20 nm. The p-DBR has 23 pairs with a reflectance of 99.57%, and the n-DBR has 39.5 pairs with a reflectance of 99.94%. Furthermore, the central wavelength of the spectrum is just at 800 nm obtained by photonic integrated circuit simulator in 3D (PICS3D) at room temperature, which agrees well with the design..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 902007 (2011)
Materials and Thin Films
Study on Electro-Optic Effect of PMN-PT Ceramics Using Goos-Hnchen Shift
Ran Maowu, Cao Zhuangqi, Chen Xianfeng, and Chen Fan
The Goos-Hnchen shift at both sides of the waveguide is conducted, which gives rise to a quadric-curve relation between Goos-Hnchen shift and the applied voltage, based on the theoretical analysis of the intrinsic loss in a symmetrical metal-cladding electro-optic waveguide. A symmetrical metal-cladding waveguide is The Goos-Hnchen shift at both sides of the waveguide is conducted, which gives rise to a quadric-curve relation between Goos-Hnchen shift and the applied voltage, based on the theoretical analysis of the intrinsic loss in a symmetrical metal-cladding electro-optic waveguide. A symmetrical metal-cladding waveguide is fabricated with a 622 μm-thick Pb(Mg1/3Nb2/3O3)-PbTiO3 (PMN-PT) transparent ceramic which serves as the guiding layer of the waveguide. Measurements of the relation between Goos-Hnchen shift and the applied voltage are carried out and the quadratic electro-optic coefficient of the PMN-PT ceramic is obtained. Experimental results are agreed well with the numerical simulations..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 906001 (2011)
Research on Surface Photovoltage Spectroscopy for Exponential Doping Transmission-Mode GaAs Photocathodes
Chen Liang, Qian Yunsheng, Chang Benkang, and Zhang Yijun
By solving the one-dimensional diffusion equation for equilibrium minority carriers of transmission-mode GaAs phtotocathodes, the equations for surface photovoltage spectroscopy of exponential and uniform doping transmission-mode GaAs photocathodes are deduced. Through metal organic chemistry vaporation deposition (MOCBy solving the one-dimensional diffusion equation for equilibrium minority carriers of transmission-mode GaAs phtotocathodes, the equations for surface photovoltage spectroscopy of exponential and uniform doping transmission-mode GaAs photocathodes are deduced. Through metal organic chemistry vaporation deposition (MOCVD) technique, two GaAs photocathodes of different doping structures with the same active layer depth are designed. By measuring and theoretically emulating the surface photovoltage spectroscopy curves for two materials, the exponential doping structure can well increase the electric diffusion length for transmission-mode GaAs photocathodes. The reason is that the internal electric field can drive the photo-excited electrons to move toward surface barriers through both diffusing and electric field drifting, thus can finally elevate the emission efficiency and the surface photovoltage spectroscopy. The difference of two surface photovoltage spectroscopy waves can be well explained by the internal energy band equations and electron scattering theory..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 906002 (2011)
Influence of the Nitrogen Pressure on Diamond-Like Carbon Film Deposited by Pulsed Laser and Its Infrared Property
Luo Le, Wang Yi, Chu Yaqiong, Gao Jian, Fang Xiaodong, and Tao Ruhua
How the nitrogen pressure in the chamber influences the diamond-like carbon (DLC) film deposited by pulsed laser deposition (PLD) and its infrared property are investigated. The DLC films are deposited on silicon substrates by pulsed laser when the nitrogen pressure in the chamber is 10-3, 10-2 and 10-1 Pa respectivelyHow the nitrogen pressure in the chamber influences the diamond-like carbon (DLC) film deposited by pulsed laser deposition (PLD) and its infrared property are investigated. The DLC films are deposited on silicon substrates by pulsed laser when the nitrogen pressure in the chamber is 10-3, 10-2 and 10-1 Pa respectively. The microstructure and composition of the DLC films are detected by the visible Raman spectroscopy and the X-ray photoelectron spectroscopy (XPS). The topography of the DLC films is detected by the atomic force microscopy (AFM). The infrared transmission spectra of the DLC film is detected by the Fourier transform infrared (FTIR) spectroscopy. The experimental results demonstrate when the nitrogen pressure is enhanced from 10-3 Pa to 10-1 Pa, the fraction of sp3 bonded carbon atoms should increase in the DLC films, the fraction of C－O and C＝O should decrease, the size of graphitic crystallites should decrease and the roughness of the DLC films should increase remarkably. At the same time, the infrared antireflection rate of the DLC films should decrease and the infrared antireflection range should become narrow when the nitrogen pressure is enhanced from 10-3 Pa to 10-1 Pa..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 907001 (2011)
Effect of Variable Partial Pressure of Oxygen for SrTiO3 Thin Films Using Pulsed Laser Deposition
Wan Xiaojing, Wang Li, Chen Jiangbo, Su Xueqiong, and Kong Le
SrTiO3(STO) thin films are manufactured on LaAlO3 (100) substrates by pulsed laser deposition (PLD) with different partial pressures of oxygen. The films′ microstructure, surface morphology and optical characteristics are characterized. In accordance with the above results, the partial pressures of oxygen is an importaSrTiO3(STO) thin films are manufactured on LaAlO3 (100) substrates by pulsed laser deposition (PLD) with different partial pressures of oxygen. The films′ microstructure, surface morphology and optical characteristics are characterized. In accordance with the above results, the partial pressures of oxygen is an important process parameter for the preparation of STO thin films by PLD. With decreasing partial pressure of oxygen, the crystallinity of the thin films has ameliorated, and the structure changes from cubic to tetragonal. Film grain size gradually increases, film grain number and film thickness decrease when the partial pressure of oxygen rises. The STO films present a low optical absorption in the 400~2500 nm wavelength range. The band gap energy of the STO films deposited at 5, 10 and 15 Pa are 3.84, 4.13 and 4.05 eV, respectively. This can provide good experimental data to the further analysis of STO thin films..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 907002 (2011)
Measurement and Metrology
Experimentation of Diffuse Reflection Laser Ranging of Space Debris
Li Yuqiang, Li Zhulian, Fu Honglin, Zheng Xiangming, He Shaohui, Zhai Dongsheng, and Xiong Yaoheng
Spacecrafts in orbit are being threatened by space debris, so many countries have developed detection technique for space debris, and the diffuse reflection laser ranging of space debris is a new technology. According to the characteristic, the development and the status in the world of space debris diffuse reflection Spacecrafts in orbit are being threatened by space debris, so many countries have developed detection technique for space debris, and the diffuse reflection laser ranging of space debris is a new technology. According to the characteristic, the development and the status in the world of space debris diffuse reflection laser ranging, we research the diffuse reflection laser ranging system at Yunnan Observatory. The probability of detecting space debris by diffuse reflection laser ranging at Yunnan Observatory and the structure of systems and the key techniques for diffuse reflection laser ranging are analyzed. The feasibility of space debris diffuse reflection laser ranging at Yunnan Observatory is confirmed by experimentation method. Measurement data indicate that the precision of diffuse reflection laser ranging is 50～250 cm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 908001 (2011)
Measurement of Geometric Error of Machine Tool Guideway System Based on Laser Tracker
Zhang Zhenjiu, Hu Hong, and Liu Xin
A method for measuring geometric error components based on laser tracker is proposed for error compensation of machine tool guideway system. Homogeneous transformation is used to establish the mathematical error model of the guide way system which can comprehensively describe the relationship between the geometric erroA method for measuring geometric error components based on laser tracker is proposed for error compensation of machine tool guideway system. Homogeneous transformation is used to establish the mathematical error model of the guide way system which can comprehensively describe the relationship between the geometric error components and the volumetric errors. Three noncollinear points are selected from the stage of guideway system, and the spatial coordinates of these points are collected by laser tracker. Then the mathematical error model is applied inversely to establish a system of equations including all the geometric error components of guideway system, and finally the error components can be obtained by solving this system of equations. The measuring results achieved by the proposed method are in coincidence with those achieved by traditional nine-line method, and the difference is smaller than 0.74″, which validates the effectiveness of this method. Compared with the traditional methods, the laser-tracker-based geometric error components measuring method for guideway system is easy to implement..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 908002 (2011)
Analysis of PointDiffraction Wavefront Error Based on Finite Difference Time Domain Method
Chen Chen, Yang Yongying, Wang Daodang, and Zhuo Yongmo
The dimension of pinhole affects the error of diffraction wavefront, which is the critical element that determines the precision of point diffraction interferometer (PDI). The deviation of diffracted wavefront from an ideal sphere at visible wavelength, which is aroused by the dimension of the pinhole, is numerically aThe dimension of pinhole affects the error of diffraction wavefront, which is the critical element that determines the precision of point diffraction interferometer (PDI). The deviation of diffracted wavefront from an ideal sphere at visible wavelength, which is aroused by the dimension of the pinhole, is numerically analyzed based on the finite difference time domain (FDTD) method. The simulation results show that the peaktovalley (PV) value of diffraction wavefront error is less than 1 nm and the root mean square (RMS) value is less than 0.35 nm when the diameter of pinhole is 400 nm and numerical aperture (NA) is 0.65. The high precision of testing spherical surfaces with high NA is demonstrated. The analysis of pointdiffraction wavefront error with FDTD method provides theoretical basis for choosing the dimension of pinhole in experiments and tests with PDI..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 908003 (2011)
Experimental Study of Aromatic Explosive Sensor Based on Fluorescence Quenching
Chu Fenghong, Ye Lei, and Yang Junjie
An aromatic explosives sensor system based on fluorescence quenching method is reported. MEH-PPV is used as fluorescence indictor and plastic optical fiber as sensor head and light transmitting element. Fluorescence lifetime of fluorescence indictor measured by phase shifting method is used to detect the explosives conAn aromatic explosives sensor system based on fluorescence quenching method is reported. MEH-PPV is used as fluorescence indictor and plastic optical fiber as sensor head and light transmitting element. Fluorescence lifetime of fluorescence indictor measured by phase shifting method is used to detect the explosives concentration. The effect of fluorescence indictor concentration on system sensitivity is measured, and we find that when MEH-PPV concentration is 10 mg/L the system sensitivity reaches the highest point. We also measure the system sensitivity under different shaped sensor heads (U-shaped, biconical-shaped, spiral-shaped), and it is found that biconical-shaped is most suitable for the sensing system. The stability of MEH-PPV is studied, and the experimental results indicate that the bleaching rate of fluorescence indictor will get faster under the exposure of daylight..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 908004 (2011)
Noise Analysis of Staring Three-Dimensinal Active Imaging Laser Radar
Zhou Qin, Zhang Xiuda, Hu Jian, and Yan Huimin
Intensified change coupled device (ICCD) is one of the key devices in the staring three-dimensinal (3D) active imaging laser radar. The intensity and noises were measured with different input light intensities and different intensified gain voltages. According to the photoelectric detection process, the measured intensIntensified change coupled device (ICCD) is one of the key devices in the staring three-dimensinal (3D) active imaging laser radar. The intensity and noises were measured with different input light intensities and different intensified gain voltages. According to the photoelectric detection process, the measured intensity and noises are analyzed with Poisson random process theory and the least square fitting method. It is found out that the noises consist of the equivalent photoelectron shot noise from the image intensifier and the photoelectron shot noise from the charge coupled device (CCD). Although the optical signal is magnified by the image intensifier, the latter part of noise can not be neglected in most cases. A noise model of 3D imaging with a doubly stochastic Poisson process is established, from which the optimal range-modulated gain function with a minimum distance error is deduced..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 908005 (2011)
Thermal Lens Determination in SolidState Laser by Using Astigmatic Cavity
Zheng Yaohui, Wang Yajun, and Peng Kunchi
A simple method using an astigmatic cavity to determine the thermal lens of laser crystals is reported. At certain resonator parameters there is a certain thermal focal length, which meets the requirement of making the beam size equal at the tangential and sagittal planes. Based on the ABCD matrix, the relation betweenA simple method using an astigmatic cavity to determine the thermal lens of laser crystals is reported. At certain resonator parameters there is a certain thermal focal length, which meets the requirement of making the beam size equal at the tangential and sagittal planes. Based on the ABCD matrix, the relation between the cavity length and the focal length is obtained. The relation between the cavity length and the pump power can be established by observing the spot pattern. Thus, the thermal lens length can be obtained by a middle parameter, that is, the cavity length..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 908006 (2011)
Sequential Detection of Targets in Laser Active Imaging System
Li Xiaofeng, Xu Jun, Luo Jijun, Cao Lijia, Zhang Shengxiu, and Zhang Ying
To solve the target detection problem caused by the low signal-to-noise ratio (SNR) of the laser active imaging system, a multichannel sequential detection algorithm is presented. Based on the original observed data, the calculation for judging threshold of laser active imaging system is proposed according to the generTo solve the target detection problem caused by the low signal-to-noise ratio (SNR) of the laser active imaging system, a multichannel sequential detection algorithm is presented. Based on the original observed data, the calculation for judging threshold of laser active imaging system is proposed according to the generalized log-likelihood ratio. The multichannel characteristics of laser active imaging system are considered and the sequential probability ratio test (SPRT) is implemented to detect the targets in intensity image channel and range image channel, while controlling the rates of false alarms and missed detections. Theoretical analysis and experimental results show that the performance of the multichannel sequential detection algorithm is excellent. The results allow us to conclude that the use of the sequential detection algorithm substantially reduces the required time and the sample size of the system. This new target detection method satisfies the accuracy and real time requirements for laser active imaging guidance..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 908007 (2011)
Repeatability of Transmittance and Reflectance Measurement of Two Path and Correlation System
Zhang Chunxiang, Yang Lin, Hui Hongchao, Guo Yajing, Tang Shunxing, Miao Jie, and Zhu Baoqiang
A two path and self-correlation system is designed to measure reflectance and transmittance. In order to verify and modify the stability of this system, repeatability of reflectance and transmittance for single-point is tested and analyzed by using of three different laser sources, and it concludes that the power and pA two path and self-correlation system is designed to measure reflectance and transmittance. In order to verify and modify the stability of this system, repeatability of reflectance and transmittance for single-point is tested and analyzed by using of three different laser sources, and it concludes that the power and polarization stability of the system does little reaction with system repeatability. Stability is enhanced based on experimental analysis, what’s more, system accuracy is calibrated. The result turns out that the uncertainty is stabilized at 0.04%, which fits well with the accuracy requirement of uniformity measurement on large-aperture optics with low transmittance or reflectance, and concrete parameter selections are provided to the instrument design of this kind..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 908008 (2011)
A New Method of Actively Modifying the Grating to Improve the Accuracy of On-Line Three-Dimensional Inspection
Wu Yingchun, Cao Yiping, and Xiao Yanshan
A new method of actively modifying the periods of projected grating in divergent lighting system is proposed. In the on-line three-dimensional (3D) inspection with phase measuring profilometry (PMP) based on Stoilov algorithm, the divergent lighting system results in the non-constant period of the fringe pattern on theA new method of actively modifying the periods of projected grating in divergent lighting system is proposed. In the on-line three-dimensional (3D) inspection with phase measuring profilometry (PMP) based on Stoilov algorithm, the divergent lighting system results in the non-constant period of the fringe pattern on the reference plane, which will lower the measurement accuracy. Therefore, a novel method about modifying the periods of the projected grating is proposed, which improves the flexibility and accuracy of the on-line 3D inspection and avoids the complicated calculation and measurement of the system parameter. Through analyzing the wrapped phase distribution of reference plane with static PMP, modifying the periods of the projected grating gradually by iterative algorithm, the constant period of fringe pattern on the reference plane is achieved. Experiment proves the feasibility of this method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 908009 (2011)
Micro and Nano Optics
Tunable Localized Surface Plasmon Resonance of Gold Nanoshell Particle
Zhang Xingfang, Zhang Lamei, Fan Qunfang, Liao Yanlin, Chen Xiaodong, and Mao Qinghe
Tunable characteristics of the localized surface plasmon resonance (LSPR) peak of gold nanoshells are investigated numerically with Mie theory. The results show that, for a nanoshell with fixed inner radius, the LSPR peak of gold nanoshell may be controlled by changing the thickness of the shell to adjust the strength Tunable characteristics of the localized surface plasmon resonance (LSPR) peak of gold nanoshells are investigated numerically with Mie theory. The results show that, for a nanoshell with fixed inner radius, the LSPR peak of gold nanoshell may be controlled by changing the thickness of the shell to adjust the strength of the hybridization effect which makes the LSPR peak red-shift. As the ratio of the nanoshell thickness to the nanoshell inner radius decreases, the absorption component in whole extinction spectra for nanoshells with different inner radii all increases. In addition, when the hybridization effect is used to adjust the LSPR dipole peak position, the available maximum wavelength scope is determined by the nanoshell inner radius. The larger the inner radius is, the wider the available maximum wavelength scope is..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 910001 (2011)
Optical Communication
Research on Fiber Gas Sensor System Based on Scanning Light Source
Qi Jie, Dong Xiaopeng, Shen Yanxin, and Zheng Junda
An optical-fiber gas sensor system based on narrowband scanning light source is proposed. It can complete the concentration detection of various gases mixed in the environment. As usual, traditional fiber gas sensor system requires multiple light sources for detection when there are several different kinds of gases. ByAn optical-fiber gas sensor system based on narrowband scanning light source is proposed. It can complete the concentration detection of various gases mixed in the environment. As usual, traditional fiber gas sensor system requires multiple light sources for detection when there are several different kinds of gases. By using scanning light source, the cost of industrialization gas detection can be reduced. Using an Amplified Spontaneous Emission (ASE) source as foundmental instrument, combining tunable Fabry-Perot filter driven by saw-tooth wave (STW), narrowband scanning light is generated. As the Fabry-Perot tunable filter is a capacitive device, it can cause the linear distortion of the saw-tooth wave. Parallel resonant circuit solutions are proposed to decrease saw-tooth wave linear distortion, thus the stability of light source scanning work is guaranteed. Experimental results show that the system can detect the gas concentration of different components which are mixed with acetylene and ammonia gas. Experimental results also show low error rate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 905001 (2011)
Study on Computing the Receiving Optical Power in Underwater Optical Wireless Communication
Wei Wei, Zhang Xiaohui, Rao Jionghui, and Wu Guangcheng
In underwater optical wireless communication (OWC), the impacts of water scattering on divergence angle and distribution of optical power are usually out of consideration in previous studies of receiving optical power. A three-dimensional distributing model for optical power is studied using the Hankel transform of theIn underwater optical wireless communication (OWC), the impacts of water scattering on divergence angle and distribution of optical power are usually out of consideration in previous studies of receiving optical power. A three-dimensional distributing model for optical power is studied using the Hankel transform of the beam spread function (BSF). Considering the geometrical wastage induced by receiver size, spatial position and receiving angle, the receiving optical power is obtained based on the distribution. Experimentation is implemented, which verifies that the method shows a better agreement with experimental data than previous methods..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 905002 (2011)
Frequency Tracking and Locking Methods in Resonator MicroOptic Gyro
Hong Lingfei, Zhang Chunxi, Feng Lishuang, Lei Ming, and Ma Yingjian
As one of the new rotation rate sensing devices, resonator microoptic gyro (RMOG), incorporating optical Sagnac effect and microelectromechanical systems (MEMS) fabrication technique, makes essential sense in promoting miniaturized and sensitive gyros. Fast and accurate frequency tracking and locking technique is quiAs one of the new rotation rate sensing devices, resonator microoptic gyro (RMOG), incorporating optical Sagnac effect and microelectromechanical systems (MEMS) fabrication technique, makes essential sense in promoting miniaturized and sensitive gyros. Fast and accurate frequency tracking and locking technique is quite important to suppress the drift induced by environmental temperature and mechanical variations. Two frequency tracking and locking methods, based on single light path (single mode) and common part of both counterpropagating light paths (common mode), are presented and applied on established RMOG system. For the single mode method, signal from single light path is detected to feedback and control the light frequency, where the influence of nonreciprocal optical noise is neglectable. However, in the latter case, the common mode of the two counterpropagating lights is used, which is a constant during the rotating state variation, representing fast frequency tracking speed. Testing results show that the frequency tracking time of 0.09 ms·［(°)/s］-1 under rotation rate variation and frequency locking precision of 0.07 °/s for over 1h by single mode and common mode frequency tracking and locking methods for the RMOG system, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 905003 (2011)
Temperature Sensor of Fiber Micro-Cavity Based on Cavity Ring-Down Spectroscopy Technology
Shang Jiabin, Zhang Weigang, and Wei Shilei
A temperature sensor of fiber micro-cavity based on the cavity ring-down spectroscopy (CRDS) technology is proposed and implemented. The micro-cavity on single mode 1060 nm fibers is achieved by direct writing with high-frequency CO2 laser pulses. As a sensor unit, the fiber micro-cavity is accessed to the fiber-loop rA temperature sensor of fiber micro-cavity based on the cavity ring-down spectroscopy (CRDS) technology is proposed and implemented. The micro-cavity on single mode 1060 nm fibers is achieved by direct writing with high-frequency CO2 laser pulses. As a sensor unit, the fiber micro-cavity is accessed to the fiber-loop resonator. Temperature sensing is realized by measuring the ring-down time of the pulsed laser. In the temperature range of 24 ℃~93 ℃, the sensitivity of the temperature sensor is up to 83.36 ns/℃. Experimental results show good linearity..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 905004 (2011)
Beam Steering Control Based on Liquid Crystal Spatial Light Modulator
Zhang Cai, Huang Yongmei, 1Qi Bo, Bian Jiang, and Wu Qiongyan
Liquid crystal spatial light modulator (LCSLM) can realize beam steering by modulating wavefront tilt. Compared with fast steering mirror (FSM), LCSLM is smaller, lighter and lower power consumptive in a nonmechanical way. Thus, it can be applied as a beam steering control device in laser communication. The principle Liquid crystal spatial light modulator (LCSLM) can realize beam steering by modulating wavefront tilt. Compared with fast steering mirror (FSM), LCSLM is smaller, lighter and lower power consumptive in a nonmechanical way. Thus, it can be applied as a beam steering control device in laser communication. The principle of liquid crystal beam steering is introduced. A closeloop control experiment is designed based on LCSLM to realize beam steering according to the modulation characteristic of LCSLM tested. The experimental results show that LCSLM can suppress jitter effectively. The relative error is less than ±1.75%. The influence of diffractive effect on beam quality is analyzed, as well as the restriction of response time of liquid crystal, transmission delay and algorithm complexity on control bandwidth..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 905005 (2011)
Improved Performance of PCF Combiners with Expanded Core-Tapered Technology
Zhou Hang, Chen Zilun, Li Jie, Hou Jing, and Chen Jinbao
A novel design of photonic crystal fiber (PCF) combiners is demonstrated. First, collapse three rings of air holes near to the fiber core using the post-processing techniques of PCFs, to enlarge the core. Then, taper it. Finally, splice the tapered multi-photonic crystal fibers into a multimode fiber for output. The axA novel design of photonic crystal fiber (PCF) combiners is demonstrated. First, collapse three rings of air holes near to the fiber core using the post-processing techniques of PCFs, to enlarge the core. Then, taper it. Finally, splice the tapered multi-photonic crystal fibers into a multimode fiber for output. The axial losses of the directly tapered combiners and the expanded core-tapered combiners at different incident wavelengths are simulated and compared. The results show that the transmission losses of the expanded core-tapered combiners are far below those of the combiners without using the technology..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 905006 (2011)
Propagation Properties of Guided Modes in an Optical Fiber with Anisotropy Metamaterials
Shen Lufa, Jiang Liping, and Wang Zihua
An optical fiber with anisotropy metamaterials in the core and a common medium in the cladding is investigated. Firstly, four dispersion equations for the oscillating guided modes based on Maxwell′s equations are obtained. From the dispersion equations, and considering frequency dispersion of practical metamaterials, sAn optical fiber with anisotropy metamaterials in the core and a common medium in the cladding is investigated. Firstly, four dispersion equations for the oscillating guided modes based on Maxwell′s equations are obtained. From the dispersion equations, and considering frequency dispersion of practical metamaterials, some dispersion curves for TE、TM、HE and EH modes are plotted. Some new dispersion properties of the oscillating guided modes are gotten by analyzing and comparing these curves, such as: the effective-refractive index increases individual with the frequency; as frequency adds, TM oscillating guided modes have a fixed velocity and EH modes always have two different group velocities and mutation frequency is 4.46 GHz. Besides, as mode number increases, the dispersive curves move along up and left direction; however, as the core radius increases, the curves turn along down and right direction and the bandwidth of HE11 oscillating guided mode becomes widely. In all words, these are interesting dispersion properties and may make a direction to design high quality fiber..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 905007 (2011)
Characteristic of Subwavelength Dielectric Grating with Metal Layer and Its Sensing Applications
Ma Weitao, Zhou Jun, Huang Shuiping, and Yuan Hongwei
The subwavelength dielectric grating-metal structure with a quartz glass substrate is proposed. It can be seen as a waveguide which is composed of metal layer, grating and superstrata according to the equivalent medium theory. With proper incident angles and light wavelengths, the total resonance absorption occurs. TheThe subwavelength dielectric grating-metal structure with a quartz glass substrate is proposed. It can be seen as a waveguide which is composed of metal layer, grating and superstrata according to the equivalent medium theory. With proper incident angles and light wavelengths, the total resonance absorption occurs. The resonance spectra of total absorption are analyzed using rigorous coupled-wave analysis (RCWA) method. The results show that the peak of TM1 mode of the waveguide is very sharp and sensitive to variation of refractivity of the superstrata. The angle sensitivity and wavelength sensitivity are 127.87\O /RIU and 409.35 nm/RIU, respectively, and the linearity between the resonance peaks and the refractivity of superstrata is good in a large range of refractive index of superstrata. Compared with guide-mode sensors of all dielectric and grating-type surface plasmon resonance sensors, the proposed structure can realize high sensitivity and the narrow resonance peaks can provide high detection precision..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 905008 (2011)
Optical Design and Fabrication
Selection of Design Theory for Near Infrared Noncollinear Acousto-Optic Tunable Filter
Zhang Chunguang, Wang Hao, and Qiu Yishen
For the different consideration of the TeO2 acousto-optic material, there are several theories of the noncollinear acousto-optic tunable filter (AOTF) design. Three relationships of noncollinear acousto-optic interaction are analyzed in this paper. The results indicate that the P. A. Gass′ theory can describe the relatFor the different consideration of the TeO2 acousto-optic material, there are several theories of the noncollinear acousto-optic tunable filter (AOTF) design. Three relationships of noncollinear acousto-optic interaction are analyzed in this paper. The results indicate that the P. A. Gass′ theory can describe the relationship of AOTF parameters, and the correlative equations are simple. On the basis of P. A. Gass′ theory, the optimization design method of the incident polar angle, the dispersion elimination and the geometry parameters are discussed. The theoretic index of the designed 0.8~2.0 μm noncollinear AOTF are better, indicating the applicability of P. A. Gass′ theory. The study is meaningful for pushing the widely applications of noncollinear AOTF..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 916001 (2011)
Spectroscopy
Near-Infrared Raman Spectroscopy for Detection of Gastric Cancer Peritoneal Dissemination in vivo
Ma Jun, Xu Ming, Gong Longjing, Gao Yuan, Mao Weizheng, and Zheng Rong′er
The nude mice injected with human gastric cancer cells (SGC-7901) in their peritoneums are chosen as animal models of gastric cancer peritoneal dissemination in this research. The Raman spectra at 785 nm excitation of both these nude mice which are in different tumor planting periods and the normal counterpart are takeThe nude mice injected with human gastric cancer cells (SGC-7901) in their peritoneums are chosen as animal models of gastric cancer peritoneal dissemination in this research. The Raman spectra at 785 nm excitation of both these nude mice which are in different tumor planting periods and the normal counterpart are taken in vivo in the imitate laparotomy. 205 spectra are collected. The spectra of different tissue types are compared and classified by support vector machine (SVM) algorithm. The results show significant differences between normal and malignant tissues. For normal and malignant tissues, the sensitivity, specificity and accuracy are 95.73%, 70.73% and 90.73%, respectively, while for different tumor planting periods, they are 98.82%, 98.73% and 98.78%. The experimental results show that Raman spectra differ significantly between cancerous and normal gastric tissues, which provides experimental basis for the diagnosis of gastric cancer by Raman spectroscopy technology. And SVM algorithm can give well generalized classification performance for the samples, which expands the application of mathematical algorithms in classification..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 915001 (2011)
On-Line Monitoring of Molten Steel Compositions by Laser-Induced Breakdown Spectroscopy
Sun Lanxiang, Yu Haibin, Xin Yong, Cong Zhibo, and Kong Haiyang
The elemental composition of Cr, Si and Mn of molten steel is on-line monitored by laser-induced breakdown spectroscopy (LIBS). Solid steel is melted in medium frequency induction furnace into liquid, and raw materials are added in the furnace to adjust the contents of Cr, Si and Mn. Based on laser-induced breakdown spThe elemental composition of Cr, Si and Mn of molten steel is on-line monitored by laser-induced breakdown spectroscopy (LIBS). Solid steel is melted in medium frequency induction furnace into liquid, and raw materials are added in the furnace to adjust the contents of Cr, Si and Mn. Based on laser-induced breakdown spectroscopy, an experimental equipment named SIA-LIBS-02 is developed and used to measure the components of molten steel. The effect of the steel temperature and component concentration on spectral line intensity is studied. The results show that the steel temperature strongly affects the intensity of different characteristic lines, the relationships between temperature and line intensity are different for different elements, and the detection capability of minor elements in molten steel is higher that in normal steel. In addition, relative line intensity can resist dynamic disturbance in on-line measuring, and successfully monitor the concentration changing of component Cr, Si and Mn in the case of constant steel temperature..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 9, 915002 (2011)
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