Journals >Chinese Journal of Lasers
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2016
Volume: 43 Issue 10
35 Article(s)
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Mode Demultiplexing Based on Multichannel Blind Least Mean Square Algorithm
Guan Liyang, and Hu Guijun
The multichannel blind least mean square (MBLMS) algorithm is proposed to implement mode demultiplexing for a 2×2 mode division multiplexing （MDM） system. The principle of MBLMS algorithm based on the non-Gaussian maximization is described. The demultiplexing performance of this algorithm is analyzed, and this algThe multichannel blind least mean square (MBLMS) algorithm is proposed to implement mode demultiplexing for a 2×2 mode division multiplexing （MDM） system. The principle of MBLMS algorithm based on the non-Gaussian maximization is described. The demultiplexing performance of this algorithm is analyzed, and this algorithm is compared with the least mean square (LMS) algorithm based on data assistance. The simulation results show that the MBLMS algorithm can realize blind separation of the convolved mixed signals without data assistance. Its demultiplexing performance is comparable with that of the LMS algorithm, and its convergence rate is improved by 33.3% compared with that of LMS algorithm based on data assistance..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1006001 (2016)
Biomedical Photonics and Laser Medicine
Effect of Optical Clearing Agent on Laser Treatment
Ma Jun, Chen Bin, Li Dong, and Wu Wenjuan
In order to study the optical clearing effect on reducing the skin scattering and increasing the laser energy reaching the target vessel, a quantitative study on the optical clearing effect of glycerol on the skin tissue phantom was conducted in the visible to infrared wavelength band. An in vitro experimental system fIn order to study the optical clearing effect on reducing the skin scattering and increasing the laser energy reaching the target vessel, a quantitative study on the optical clearing effect of glycerol on the skin tissue phantom was conducted in the visible to infrared wavelength band. An in vitro experimental system for laser treatment of port wine stain was set up to obtain quantitative relationship between optical clearing effect and the blood coagulation properties under the irradiation of multi-pulse Nd∶YAG laser. The results show that the diffuse reflectance of the skin tissue phantom decreases by 36.69% and the transmittance increases by 38.73% at 1064 nm after 0.5 mL anhydrous glycerol is applied on the skin phantom surface for 10 min. After 0.5 mL anhydrous glycerol is applied on the skin tissue phantom surface for 4 min, the number of laser pulses required for blood coagulation decreases by 25%. After application for 10 min, the number of laser pulses required for blood coagulation does not decrease further, but the blood coagulation area increases by 34.1% compared with that after 4 min. The results indicate that glycerol is effective to improve the laser treatment of port wine stain by increasing the laser energy reaching the target vessel..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1007001 (2016)
Holography and Information Processing
Augmented Reality Three-Dimensional Display System Based on Holographic Optical Element
Yu Wentao, Zhang Hanle, Deng Huan, Wang Qionghua, and Li Dahai
An augmented reality integral imaging three-dimensional (3D) display system based on holographic optical element is designed. Theoretical analysis is carried out on the record and reproduction of holographic optical element based on reflection volume holographic principle, and a holographic optical element with size ofAn augmented reality integral imaging three-dimensional (3D) display system based on holographic optical element is designed. Theoretical analysis is carried out on the record and reproduction of holographic optical element based on reflection volume holographic principle, and a holographic optical element with size of 20 mm×20 mm is recorded by setting up the experimental light path. The holographic optical element reflects the micro-lens array imaging function only for light which meets Bragg conditions, and it reproduces the virtual 3D image. The light emitted from the real 3D object can directly go through the holographic optical element. Therefore, the holographic optical element is used as an image fusion element to realize the fusion of the real 3D object and virtual 3D image. The developed optical see-through augmented reality 3D display system reproduces a better virtual 3D image and realizes the effective fusion with the real 3D object, which achieves the augmented reality 3D display effect..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1009001 (2016)
Laser Devices and Laser Physics
High-Peak-Power Rod-Type Photonic Crystal Fiber Amplifier for Picosecond Pulses
Wang Ziwei, Wang Zhaokun, Zou Feng, Wu Wendi, Li Qiurui, Bai Yang, and Zhou Jun
High-peak-power ultrashort pulse lasers are currently in demand for laser micromachining. It is an effective technique to use ultra-large-mode-field fibers to amplify the power of ultrashort laser pulses, for realizing ultrashort output laser pulses with high beam quality and high peak power. Based on a 1030 nm mode-loHigh-peak-power ultrashort pulse lasers are currently in demand for laser micromachining. It is an effective technique to use ultra-large-mode-field fibers to amplify the power of ultrashort laser pulses, for realizing ultrashort output laser pulses with high beam quality and high peak power. Based on a 1030 nm mode-locked tunable fiber laser, multi-stages of all-fiber preamplifiers and ultra-large-mode-field rod-type photonic crystal fiber (PCF), the output properties of rod-PCF amplifiers are demonstrated. The amplifier delivers near-diffraction-limit 30 ps pulses with maximum peak power of 2.94 MW..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1001001 (2016)
Optimization of Dithering Frequency Matching Technique for Mechanically Dithered Ring Laser Gyros
Ma Yanghua, Han Zonghu, and Wang Jiliang
The dithering of mechanically dithered ring laser gyro (DRLG) leads to pseudo coning motion in the strap-down inertial navigation system (SINS). The influence of the pseudo coning motion on calculation of the rotating vector of SINS is analyzed, and the formula is deduced. To minimize the pseudo coning error, the influThe dithering of mechanically dithered ring laser gyro (DRLG) leads to pseudo coning motion in the strap-down inertial navigation system (SINS). The influence of the pseudo coning motion on calculation of the rotating vector of SINS is analyzed, and the formula is deduced. To minimize the pseudo coning error, the influcence factors are analyzed by numerical calculation, and the matching principle of dithering frequency difference among different DRLGs in SINS is recommended. Based on the principle, a dithering frequency tunable technology for the practical difficulty during DRLG production is proposed and investigated numerically and experimentally. The results show that the proposed technique can meet the dithering frequecy difference matching demand of SINS by choosing one main dither motor plus appropriate adjusting components, and there is no negative impact on the overall size and the anti-vibration performace of DRLG. Compared to the conventional programs, the proposed technique promotes the productive capacity of DRLG, especially for the miniature DRLG, and reduces the production cost..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1001003 (2016)
Laser Diode End Pumped Nd:YAG Surface Gain Slab Lasers
Liu Yang, Tang Xiaojun, Wang Zhe, Wu Changjie, Zhao Hong, and Zhou Shouhuan
We designed a novel surface gain slab laser combining the characteristics of slab lasers and disk lasers. A pumping system based on image relaying along the slow axis was used to obtain the uniform distribution of pumping light in the slab width direction. We achieved stable quasi-continuous laser output with the surfaWe designed a novel surface gain slab laser combining the characteristics of slab lasers and disk lasers. A pumping system based on image relaying along the slow axis was used to obtain the uniform distribution of pumping light in the slab width direction. We achieved stable quasi-continuous laser output with the surface gain slab laser. The maximum output energy of 1064 nm laser pulse is 121.3 mJ when the pumping repetition rate is 300 Hz, the pulse width is 200 μs, and the pumping energy of a single pulse is 354 mJ. The corresponding optical-to-optical efficiency and the slope efficiency are 34.3% and 45%, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1001004 (2016)
Nanolaser Based on Hybrid Plasmonic Wavguide
Li Zhiquan, Peng Tao, Zhang Ming, Yue Zhong, Gu Erdan, Li Wenchao, Feng Dandan, and Liu Tonglei
In this paper, a nanolaser based on hybrid plasmonic waveguide is proposed, and its theoretical research and simulation analysis are carried out. In this structure, the plasma mode of metal-dielectric interface is coupled with high gain medium semiconductor nanowire waveguide mode, which greatly increases the intermediIn this paper, a nanolaser based on hybrid plasmonic waveguide is proposed, and its theoretical research and simulation analysis are carried out. In this structure, the plasma mode of metal-dielectric interface is coupled with high gain medium semiconductor nanowire waveguide mode, which greatly increases the intermediate air gap field strength and meanwhile maintains low loss transmission. And deep subwavelength constraint to output light field is realized. By optimizing the geometric parameters of the structure, a nanolaser with smaller threshold and higher quality factors is achieved. Compared with the nanolaser of edge-coupled hybrid plasmonic waveguide, the proposed nanolaser with lower threshold can be obtained when the geometric parameters of the two lasers are the same..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1001005 (2016)
Simulation of Thermal Effect in Repetitive Pulsed Laser Irradiation on Metals
Hu Peng, and Chen Faliang
Under the irradiation of repetitive pulsed lasers with different duty ratios, the temperature increase characteristic of front and back surfaces and the variation law of ablation depth are numerically simulated, and the influences of material thickness and variety are investigated. The simulation results show that the Under the irradiation of repetitive pulsed lasers with different duty ratios, the temperature increase characteristic of front and back surfaces and the variation law of ablation depth are numerically simulated, and the influences of material thickness and variety are investigated. The simulation results show that the temperature increase curve for the front surface possesses a tooth-like shape. The smaller the laser duty ratio or the thinner the material is, the higher the back surface temperature is, and the deeper the ablation depth is. Compared with the continuous-wave laser, the repetitive pulsed laser is more beneficial to heating and ablation of metals..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1001006 (2016)
High Power Passively Q-Switched Laser of Diode-Pumped Domestic Yb:YAG Ceramic
Yu Yang, Zhu Jiangfeng, Li Jiang, Gao Ziye, Wang Junli, Xie Tengfei, Pan Yubai, and Wei Zhiyi
A high power passively Q-switched laser of diode-pumped domestic Yb:YAG ceramic is reported in this paper. In the experiment, a semiconductor saturable absorber mirror (SESAM) is used as the Q-switching component, and the passively Q-switched laser pulse output is obtained under the absorbed pump power of 6.3 W. The maA high power passively Q-switched laser of diode-pumped domestic Yb:YAG ceramic is reported in this paper. In the experiment, a semiconductor saturable absorber mirror (SESAM) is used as the Q-switching component, and the passively Q-switched laser pulse output is obtained under the absorbed pump power of 6.3 W. The maximum average output power of the Q-switched laser pulses is 1.24 W, the pulses′ duration is 2.93 μs, the repetition rate is 31 kHz, and the single pulse energy is 40 μJ. By studying the performance of the domestic Yb YAG ceramics under continuous and Q-switched laser, the potential applications of domestic high-quality Yb YAG ceramics in high-power short-pulse solid-state lasers are revealed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1001007 (2016)
Output of Mid-Infrared Laser with Narrow Spectral Width in Implementation of Optical Parametric Oscillator and Oscillator Power Amplifier
Zhao Zhigang, Shen Lifeng, Jiang Hongbo, Liu Bin, Xiang Zhen, and Liu Chong
Factors such as high gain and spectral width of pump laser will significantly broaden the output parametric spectra of optical parametric oscillators (OPO). Etalons, gratings and other components are usually used to control the spectral width, however, loss will be imported, and thus the output threshold of lasers willFactors such as high gain and spectral width of pump laser will significantly broaden the output parametric spectra of optical parametric oscillators (OPO). Etalons, gratings and other components are usually used to control the spectral width, however, loss will be imported, and thus the output threshold of lasers will increase and the conversion efficiency and the output power will decrease. A scheme for obtaining mid-infrared laser with narrow spectral width and high power is reported, in which the spectral width compression components are not used. The proposed scheme obtains narrow spectral width and high power respectively. A narrow-spectral-width pump source with a 1.064 μm NdYAG main oscillator power amplifier (OPA) structure is built. By adjusting the power and the diameter of the pump light spot in PPMgLN crystal of the optical parametric oscillator, we can control the gain intensity in the crystal and the spectral width of mid-infrared laser. In the optical parametric oscillator, when the pump power is about three times of the threshold, 0.7 W, 2.9 μm seed laser with spectral width less than 1.12 nm is obtained. The seed light is amplified through two optical parametric amplifiers, and 6.27 W, 2.9 μm laser output is finally obtained, when the light conversion efficiency is 15.7% and the spectral width remains unchanged..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1001008 (2016)
Bondability Criterions of Laser Crystals
Zou Yan, Wu Ting, Li Zhitong, Hui Yongling, Jiang Menghua, Lei Hong, and Li Qiang
As laser materials, bonding crystals have an efficient thermal management. They can decrease the deformation and fracture at the end face of crystals, and reduce wavefront distortion of laser. Based on the bonding interface gap closing theory, the bondability criterions of laser crystals are analyzed, the Hamaker constAs laser materials, bonding crystals have an efficient thermal management. They can decrease the deformation and fracture at the end face of crystals, and reduce wavefront distortion of laser. Based on the bonding interface gap closing theory, the bondability criterions of laser crystals are analyzed, the Hamaker constant and surface energy are calculated when Nd∶YAG, Nd∶YVO4 and sapphire are optical contacting, the bondability criterions for the three composite crystals are discussed, and the difficulty in crystal bonding is compared. Taking the YAG-Nd∶YAG crystal for example, the optical contacting experiment verifies the rationality of the bondability criterions, and the pump experiment for the bonding crystal after heat treatment proves that the bonding strength and the bonding stability fulfill the experimental requirements. The method for judging crystal bondability criterions provides references for selecting bonding materials and optimizing bonding process parameters..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1001009 (2016)
All-Solid-State Doubly Resonant Intracavity Sum-Frequency 578 nm Yellow Laser with KTP Type Ⅱ Phase Matching
Yang Jianming, Tan Huiming, Tian Yubing, Yao Wenming, Ma Gangfei, Ju Qiaojun, Zhang Long, Chen Jiansheng, and Gao Jing
An all-solid-state doubly resonant intracavity sum-frequency continuous-wave 578 nm yellow laser with KTP type Ⅱ phase matching is studied. Two kinds of gain media, YbYAG and NdYAG, are used to generate spectral lines of the fundamental frequency at 1030 nm and 1319 nm. The 578 nm yellow laser output is achieved by intAn all-solid-state doubly resonant intracavity sum-frequency continuous-wave 578 nm yellow laser with KTP type Ⅱ phase matching is studied. Two kinds of gain media, YbYAG and NdYAG, are used to generate spectral lines of the fundamental frequency at 1030 nm and 1319 nm. The 578 nm yellow laser output is achieved by intracavity sum-frequency with KTP type Ⅱ critical phase matching. It is found in the experiment that besides the output of the yellow laser at 578 nm, an output of sum-frequency yellow laser at 582 nm is found at the same time. By spectral analysis, the phenomena are ascribed to the oscillation of 1338 nm from the transition of R2→X3 in NdYAG crystal and the sum-frequency generation (SFG) between the wavelengths of 1030 nm and 1338 nm. When the pump powers of YbYAG and NdYAG are 10.3 W and 3.7 W respectively, the yellow laser with the output power of 55 mW is obtained. The power stability of the output laser is better than 4.7% within 30 min. By using a Glan prism, the polarization characteristics of the fundamental frequency light and the sum-frequency light are measured. The results show that for the two isotropic laser crystals, both the resonator structure and the azimuth angle of the SFG crystal have influence on the polarization characteristics of the corresponding fundamental frequency light, and both of them can change the polarization direction of the fundamental frequency light to the direction which benefits to the sum-frequency process..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1001010 (2016)
Optimal Conversion Efficiency of Continuous-Wave Optical Parametric Oscillator
Jiang Hongbo, Shen Lifeng, Zhao Zhigang, Liu Bin, Xiang Zhen, Liu Dong, and Liu Chong
Optimal conversion efficiency of a continuous-wave optical parametric oscillator (OPO) is investigated experimentally. The nonlinear crystal of OPO is a magnesia-doped periodic polarization lithium niobate crystal. As the power density inside the OPO cavity is associated with the reflectivity of the cavity mirrors, difOptimal conversion efficiency of a continuous-wave optical parametric oscillator (OPO) is investigated experimentally. The nonlinear crystal of OPO is a magnesia-doped periodic polarization lithium niobate crystal. As the power density inside the OPO cavity is associated with the reflectivity of the cavity mirrors, different cavity mirrors are used. Experimental results show that the best intensity inside the cavity exists to obtain the best conversion efficiency. By the coupling of the pump power and the OPO cavity, 8 W idler output at 2.9 μm with the efficiency of 19.5% is achieved. The spectral width of the 2.9 μm laser is less than 0.68 nm without any additional bandwidth control elements..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1001011 (2016)
Design of High Brightness Fiber-Coupled Diode Laser System Based on Dual-Emitters
Wu Hualing, Guo Linhui, Wang Zhao, Yu Junhong, Gao Songxin, and Wu Deyong
Fiber-coupled diode laser output system is often used for pumping source of fiber laser, and it is one of the key elements of fiber laser. Aimed at multi-mode fiber of 105 μm core diameter and 0.15 numerical aperture, a high brightness fiber-coupled diode laser system based on dual-emitters is designed by using Zemax sFiber-coupled diode laser output system is often used for pumping source of fiber laser, and it is one of the key elements of fiber laser. Aimed at multi-mode fiber of 105 μm core diameter and 0.15 numerical aperture, a high brightness fiber-coupled diode laser system based on dual-emitters is designed by using Zemax software. In the system, the high precision collimation technique, spatial multiplexing used steps and mirrors, polarization multiplexing and slow axis beam expander technique are taken to achieve beam shaping. Finally, an aspherical lens is used to focus and couple the beam into the target fiber of 105 μm core diameter and 0.15 numerical aperture. Combined with the design, the equivalent confirmatory experiment is carried out based on the existing experimental condition. The simulation and experiment all show that, the system can couple 16 dual-emitters into a fiber of 105 μm core diameter and 0.15 numerical aperture, the stable output power can reach 154 W, the brightness is up to 25 MW/( cm2·sr), and the electro-optics efficiency is 42% at injection current 15 A. This system can be widely used in pumping fiber laser, manufacture processing and other fields after been engineered..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1001012 (2016)
Laser Manufacturing
Experimental Study on Laser Deposition Repair of Surface Damage of GH4169 Thin-Walled Components
Bian Hongyou, Dong Wenqi, Wang Shijie, Qu Shen, Yang Guang, Qin Lanyun, and Wang Wei
The effects of substrate thickness and scanning mode on the residual stress, microstructure, and tensile property of GH4169 alloy components after laser deposition repair (LDR) are investigated. The results show that the smaller the substrate thickness or the larger the deposition thickness is，the larger both the residThe effects of substrate thickness and scanning mode on the residual stress, microstructure, and tensile property of GH4169 alloy components after laser deposition repair (LDR) are investigated. The results show that the smaller the substrate thickness or the larger the deposition thickness is，the larger both the residual stress and the volume fraction of the interdendritic Laves phase are, in contrast, the smaller both the tensile strength and the percentage elongation after fracture at room temperature are. The experiment indicates that the short edge scanning mode is beneficial to improving the tensile property at room temperature of GH4169 alloy after LDR..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1002002 (2016)
Effect of Temperature on Surface Mechanical Property of 2024 Aluminum Alloy Treated by Laser Peening
Meng Xiankai, Zhou Jianzhong, Su Chun, Huang Shu, Sheng Jie, Chen Hansong, and Xu Jiale
Laser peening (LP) is conducted on aeronautical 2024-T351 aluminum alloy under different temperatures, and the influence law of temperature on its surface mechanical property is studied. In combination with the microstructure analysis, the strengthening mechanism of 2024-T351 aluminum alloy treated by warm laser peeninLaser peening (LP) is conducted on aeronautical 2024-T351 aluminum alloy under different temperatures, and the influence law of temperature on its surface mechanical property is studied. In combination with the microstructure analysis, the strengthening mechanism of 2024-T351 aluminum alloy treated by warm laser peening (WLP) is revealed. The results indicate that the micro-hardness of aeronautical 2024-T351 aluminum alloy increases with the increment of peening temperature. The dispersion strengthening effect makes the amplitude of residual compressive stress induced by 120 ℃-WLP much higher than that by room-temperature LP..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1002003 (2016)
Study on Laser Welding Process of Nickel Sheet Molten Pool with Frontal Supply and Double-Sided Protection
Shi Yan, Li Zhen, Liu Jia, and Chen Junke
The laser welding process of Ni201 sheet with single-sided gas supply and double-sided forming is studied, and the welds are tested and analyzed. The results show that the weld is well-formed, the influence of groove depth on weld width is weak, and the weld zone is coarse austenite structure. The result of stomatal tyThe laser welding process of Ni201 sheet with single-sided gas supply and double-sided forming is studied, and the welds are tested and analyzed. The results show that the weld is well-formed, the influence of groove depth on weld width is weak, and the weld zone is coarse austenite structure. The result of stomatal type detection shows that the type of weld porosity is oxygen hole, and the mass fraction of oxygen versus groove depth presents a V typed change. When the groove depth is 3 mm, the oxygen mass fraction of welds is the smallest, the joint strength reaches to 377.7 MPa, which is about 80% of the base metal strength, and the welding parts meet the requirements of use..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1002004 (2016)
Damage Mechanism of Hybrid Welded 7020 Aluminium Alloy Based on Three-Dimensional X-Ray Micro-Tomography and GTN Model
Duan Hao, Wu Shengchuan, Xu Zhongwei, Zhang Zhiliang, Kan Qianhua, Kang Guozheng, and Fu Yanan
By the high resolution synchrotron radiation X-ray three-dimensional micro-tomography technology, the porosity in laser-arc hybrid welds is characterized, which is taken as the initial void volume fraction in the GTN mesoscopic damage model. The finite element models of mesoscopic damage mechanics for hybrid welded joiBy the high resolution synchrotron radiation X-ray three-dimensional micro-tomography technology, the porosity in laser-arc hybrid welds is characterized, which is taken as the initial void volume fraction in the GTN mesoscopic damage model. The finite element models of mesoscopic damage mechanics for hybrid welded joints with and without reinforcement are developed, and the principal stress and the void volume fraction distribution of tensile joints are obtained. Via the metallographic structure analysis of tensile fractures, it is shown that the geometrical and material discontinuity is the important reason for joint failure..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1002005 (2016)
Micromorphology and Crystallinity of Nano-Graphite Transformation Products After Laser Irradiation
Luo Fang, Wang Weibin, Lu Xiaoxiao, and Yao Jianhua
The nano-graphite particles are preset on the silicon substrate and irradiated by 500 W fiber laser under the protection of argon gas. The micromorphology and crystal structure of transformation products after laser irradiation are studied with different laser energy densities. Transmission electron microscopy (TEM), RThe nano-graphite particles are preset on the silicon substrate and irradiated by 500 W fiber laser under the protection of argon gas. The micromorphology and crystal structure of transformation products after laser irradiation are studied with different laser energy densities. Transmission electron microscopy (TEM), Raman spectra and X-ray diffraction are used to analyze the micromorphology and crystallinity of transformation products. When the laser energy density reaches to 3.33 kJ/cm2, the particle sizes of the transformation products become bigger than that of the original. When the laser energy density reaches to 4.17 kJ/cm2, the linear morphology can be observed on the surface of samples. When the laser energy density reaches to 8.33 kJ/cm2, the original polycrystalline structures of transformation products is transformed into massy crystal structures. The results show that the laser energy density can significantly affect the micromorphology and crystal structure transformation of the nano-graphite particles on the silicon substrate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1002006 (2016)
Experiment on Selective Laser Melting Forming of Al2O3 Ceramics
Zhang Kai, Liu Tingting, Liao Wenhe, Zhang Changdong, Yan Yishuai, and Du Daozhong
The technology of selective laser melting is used to conduct the basic experimental study on Al2O3 powders and slurry. The experimental results show that the forming effect of Al2O3 powder is worser, and in contrast that of Al2O3 slurry is better. Laser power has important impact on the surface quality of Al2O3 slurry The technology of selective laser melting is used to conduct the basic experimental study on Al2O3 powders and slurry. The experimental results show that the forming effect of Al2O3 powder is worser, and in contrast that of Al2O3 slurry is better. Laser power has important impact on the surface quality of Al2O3 slurry samples, and the surface quality continuously upgrades with the increment of laser power. With the laser power of 200 W and scanning speed of 90 mm/s, the average Vickers hardness of Al2O3 sample is about 14.7 GPa..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1002007 (2016)
Materials and Thin Films
Influence of Oxygenating Port Position on Properties of HfO2 Films Deposited by Electron Beam Evaporation
Zheng Ruxi, Yi Kui, Fan Zhengxiu, Shao Jianda, and Tu Feifei
Oxygenating port position directly affects the distribution of oxygen in the vacuum chamber, and then has significant impact on the optical performance of the film. To study the influence of oxygenating port position on the properties of HfO2 films, the HfO2 films are deposited on the silica substrates by electron beamOxygenating port position directly affects the distribution of oxygen in the vacuum chamber, and then has significant impact on the optical performance of the film. To study the influence of oxygenating port position on the properties of HfO2 films, the HfO2 films are deposited on the silica substrates by electron beam evaporation technology at two typical oxygenating port positions. Ultraviolet-visible spectrophotometer and X-ray photoelectron spectrometer are employed to study the optical properties and the chemical components of HfO2 films prepared at different oxygenating port positions. The experimental results show that providing oxygenating port in the vicinity of the substrate is more conducive to obtain good compactness and full oxidation of HfO2 films. A simplified model is established according to the configuration of the actual vacuum chamber. The turbulence model of k-ε quadratic equation is applied to carry on three-dimensional numerical simulation calculation on the distribution of oxygen in the coating process. The theoretical calculation fits well with the experimental results..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1003001 (2016)
Influence of Annealing on Interface Diffusion and Anti-Chemica-Cleaning Property of Metal-Dielectric Multilayer Films
Zhang Hong, Jin Yunxia, Kong Fanyu, Huang Haopeng, Cui Yun, Hu Guoxing, Li Xiangtan, Ge Wenna, and Ye Bangjiao
Samples of metal-dielectric multilayer films are post-annealed at different temperatures. It is experimentally found that at the annealing temperature of 350 ℃, a transition layer between Au layer and SiO2 layer of the samples occurs, and these samples possess the strong anti-chemical-cleaning ability. Based on the invSamples of metal-dielectric multilayer films are post-annealed at different temperatures. It is experimentally found that at the annealing temperature of 350 ℃, a transition layer between Au layer and SiO2 layer of the samples occurs, and these samples possess the strong anti-chemical-cleaning ability. Based on the investigation by a transmission electron microscope and the analysis by an energy dispersive spectrometer, it is found that the occurrence of transition layers is mainly the result of Cr atoms diffusing from the Au bottom layer to the SiO2 layer. The transition layer can enhance the adhesion between the Au layer and SiO2 layer and block the infiltration of acid solutions, thus the anti-chemical-cleaning ability of metal-dielectric multilayer films is enhanced..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1003002 (2016)
Measurement and Metrology
Non-Contact Photoelectric Angle Measurement Based on Gyrorotor
Wang Xianhua, Jia Sen, Gao Limin, Xiao Maosen, and Wu Yiming
A non-contact angle measurement method based on gyrorotor with periodical pattern surface is proposed. By using photoelectric sensors to detect the information from periodical pattern surface of gyrorotor, we can measure the deflection angle of gyrorotor in real time. The angle measurement principle and its device are A non-contact angle measurement method based on gyrorotor with periodical pattern surface is proposed. By using photoelectric sensors to detect the information from periodical pattern surface of gyrorotor, we can measure the deflection angle of gyrorotor in real time. The angle measurement principle and its device are introduced. By constructing three-dimensional geometrical models, the angle decoding algorithm of the angle measurement method is derived in detail, and the curves or the surfaces of the relationships between the gyrorotor′s pattern surface information detected by photoelectric sensors and the angle deflections (calculated under the conditions that the gyrorotor is without deflection, with one-dimensional deflection and with two-dimensional deflection respectively) are obtained. The results show that the deflection angle and the deflection direction of gyrorotor can be measured by two photoelectric sensors in orthogonal directions, and the measurement values are unique and the measurement range of deflection angle is larger than 30°. This method can be used to measure angle deflection both in static and high-speed dynamic measurements..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1004001 (2016)
Laser Measurement Method and in-situ Experiment of Underground Energy Storage Caverns Volume
Lü Xiaoning, Liu Xiaoli, Duan Yunling, and Liang Jianyi
Quickly and accurately measuring the volume of large underground energy storage caverns is not only a method to test the scientific rationality of engineering design and construction achievement, it is also the basic requirement for energy storage and transportation engineering and the foundation of the dynamic controlQuickly and accurately measuring the volume of large underground energy storage caverns is not only a method to test the scientific rationality of engineering design and construction achievement, it is also the basic requirement for energy storage and transportation engineering and the foundation of the dynamic control during operation depot. In order to quickly and accurately obtain the storage caverns volume and the elevation-cumulative volume curve in centimeter level, a laser sophisticated measurement system (LSMS) based on cross section and the corresponding data processing method are developed. The method is successfully applied in the volume measurement of underground energy storage caverns and the elevation-cumulative volume curve in centimeter level is achieved. The true volume is estimated by regression analysis and the volume measurement accuracy can reach -0.06%, which is one order of magnitude better than the regulatory requirements. Combined with the experimental data of total station and terrestrial 3D laser scanner, eight technical specifications are comparatively analyzed. The feasibility and correctness of the laser sophisticated measurement system and the corresponding data processing algorithm are verified..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1004002 (2016)
Experimental Research on Chromatic Dispersion Measurement Based on Digital Phase Detector
Li Yun, Xi Lixia, Zhang Xiaoguang, Tang Xianfeng, and Wan Dong
In order to improve chromatic dispersion (CD) measurement accuracy and reduce cost, a chromatic dispersion measurement method based on digital phase detector is proposed. The traditional analog phase detector is replaced by an analog to digital converter with low sampling rate and a digital phase detecting algorithm baIn order to improve chromatic dispersion (CD) measurement accuracy and reduce cost, a chromatic dispersion measurement method based on digital phase detector is proposed. The traditional analog phase detector is replaced by an analog to digital converter with low sampling rate and a digital phase detecting algorithm based on all phase fast Fourier transform (FFT), and a particle swarm optimization (PSO) algorithm is applied to the process of curve fitting. High accuracy chromatic dispersion measurement is achieved. The effects of sampling rate, signal noise ratio and FFT length on digital phase detection accuracy are also analyzed. Experiments on verifying the accuracy of the measurement system are carried out. Experiment results show that the accumulated chromatic dispersion uncertainty of G.652 fiber with different lengths at 1550 nm is less than 10 ps/nm, which is better than that of the commercial CD analyzer in metropolitan area network environment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1004003 (2016)
Optical Communication
Fast Solution of Fiber Core Conduction Mode in Multimode Step-Index Fiber
Shi Chen, Wang Xiaolin, and Lu Qisheng
The solution of characteristic equation of multimode step-index fiber core conduction mode is involved in many cases, such as the mode dispersion solution of multimode fiber, the theory analysis of optical fiber coupled-mode, and the mode evolution of tapered fiber. The large computation capability of this solution affThe solution of characteristic equation of multimode step-index fiber core conduction mode is involved in many cases, such as the mode dispersion solution of multimode fiber, the theory analysis of optical fiber coupled-mode, and the mode evolution of tapered fiber. The large computation capability of this solution affects the whole computational efficiency directly. The Newton-Raphson iteration method is analyzed and it has obvious advantage in convergence speed. In the solving process of scalar mode characteristic equation under the weak-guidance approximation, we use the zero point of the type I Bessel function to determine the interval of roots, then solve the characteristic equation quickly in the interval by combining the Newton-Raphson iteration method. The solving process is introduced in the solving of vector mode characteristic equation, and its first root and last root are determined quickly by combining the way of upper and lower boundary chord intercept. Finally, we compare the calculation results of our method with the results of OptiFiber software, draw the mode dispersion curve of fiber, and verify the accuracy of our method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1006002 (2016)
Cooperative Schemes in All-Optical Free-Space Optical Communication System
Han Liqiang, and You Yahui
A fundamental structure of all-optical free-space optical communication (FSO) system is presented. The system adopts subcarrier intensity modulation and all-optical amplify-and-forward relaying, and furthermore, it considers the effect of background noise and amplified spontaneous emission noise. A system model of the A fundamental structure of all-optical free-space optical communication (FSO) system is presented. The system adopts subcarrier intensity modulation and all-optical amplify-and-forward relaying, and furthermore, it considers the effect of background noise and amplified spontaneous emission noise. A system model of the all-optical relaying FSO system under Gamma-Gamma turbulence condition is established. Two novel cooperative schemes, all-active relaying scheme and selective relaying scheme, are presented, and their corresponding power allocation modes are provided. The outage probability of the relay-assisted transmission is compared with that of the direct link, and the outage probability of the two schemes for different channel parameters and number of relays is analyzed by simulation. The simulation results show that the performance of the link can be improved obviously by the relayed transmission, and the performance of the selective relaying scheme is superior to that of the all-active relaying scheme..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1006004 (2016)
Reviews
Research Status of Passively Mode-locked Laser Based on Nd3+-doped Disordered Crystals
He Kunna, Li Dehua, and Wei Zhiyi
An effective way to realize an ultra-short pulse is to use the passively mode-locked technology of all-solid-state lasers. Among the studies on the passively mode-locked Nd3+-doped lasers, the disordered crystals have been becoming a research hotspot. In combination with related works, the research status of passively An effective way to realize an ultra-short pulse is to use the passively mode-locked technology of all-solid-state lasers. Among the studies on the passively mode-locked Nd3+-doped lasers, the disordered crystals have been becoming a research hotspot. In combination with related works, the research status of passively mode-locked lasers based on Nd3+-doped disordered crystals are summarized, and the future prospect on the application of Nd3+-doped disordered crystals in the generation of ultra-short and ultra-intense pulses is discussed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1000001 (2016)
Remote Sensing and Sensors
Disturbed Fiber Vibration Sensor Based on 3×3 Michelson Interferometer
Cao Yulong, Yang Fei, Xu Dan, Ye Qing, and Cai Haiwen
A distributed fiber vibration sensor based on 3×3 Michelson interferometer is proposed, and a 3×3 interferometer is used to build the structure of a phase sensitive optical time domain reflectometer (φ-OTDR) based on homodyne coherent detection. With transfer matrix phase demodulation algorithm and through thA distributed fiber vibration sensor based on 3×3 Michelson interferometer is proposed, and a 3×3 interferometer is used to build the structure of a phase sensitive optical time domain reflectometer (φ-OTDR) based on homodyne coherent detection. With transfer matrix phase demodulation algorithm and through the basic parameters of the 3×3 interferometer transmission matrix, the corresponding relationship between differential phase and interferometer output light intensity is established. The simple and efficient software computing programs are used to demodulate the differential phase of Rayleigh scattering light in optical fiber, so as to realize the optical fiber distributed disturbance detection. The system is also used to detect the vibration along the fiber, and the experimental results show that the sensing system can accurately locate for the vibration and restore the frequencies of audio and radio frequency drivers, of which the effective sensing distance is 10 km..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1010001 (2016)
Wavelength Demodulation for Distributed Feedback Active Fiber Grating Sensor Based on Wavelength Scanning
Liu Pengfei, Hao Fenghuan, He Shaoling, Liu Rui, and Ge Huiliang
A wavelength demodulation method for the active fiber grating sensor is proposed. A tunable filter is used for wavelength scanning, and an etalon is used for wavelength calibration in this method. The corresponding demodulation system is set up. The feasibility of the demodulation method and the accuracy and stability A wavelength demodulation method for the active fiber grating sensor is proposed. A tunable filter is used for wavelength scanning, and an etalon is used for wavelength calibration in this method. The corresponding demodulation system is set up. The feasibility of the demodulation method and the accuracy and stability of the demodulation system are verified experimentally. The results show that the proposed method can measure the wavelength of the active fiber grating accurately. When the wavelength range is from 1533 nm to 1550 nm, the accuracy of the demodulation system is higher than 6 pm, and the fluctuation range is within ±5.7 pm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1010002 (2016)
Large Capacity and Fast FBG Sensing System Based on Marshalling Measurement and Edge Filter
Cao Pinqi, and Xu Guoliang
A fast fiber Bragg grating (FBG) sensing system with large capacity based on marshalling measurement and edge filter is designed. Sensing gratings in traditional time division multiplexing systems are grouped according to their positions on the fiber, and these grating groups are then successively measured. The limit oA fast fiber Bragg grating (FBG) sensing system with large capacity based on marshalling measurement and edge filter is designed. Sensing gratings in traditional time division multiplexing systems are grouped according to their positions on the fiber, and these grating groups are then successively measured. The limit of detector′s dynamic range in single measurement is avoided, the reutilization of sensing gratings is realized, and the measuring distance is extended. Meantime, by using edge filtering method, fast wavelength demodulation is achieved, and the wavelength signals of all gratings in one grating group is measured once, which can reduce measurement time and improve the scanning frequency of the system effectively. The result shows that a demodulation linearity of 0.9913 is realized in the temperature sensing test of the system and the error is less than 1.36 ℃..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1010003 (2016)
All-Silica Fiber EFPI High Static Pressure Sensor in Fusion with Simple Structure
Zhang Jie, Jing Zhenguo, Li Ang, and Peng Wei
All-silica fiber extrinsic Fabry-Perot interferometer (EFPI) high static pressure sensor in fusion with simple structure is introduced. The pressure effect of the sensor is theoretically analyzed, and the design structure and manufacturing process of the sensor are given. The sensor has some advantages such as long cavAll-silica fiber extrinsic Fabry-Perot interferometer (EFPI) high static pressure sensor in fusion with simple structure is introduced. The pressure effect of the sensor is theoretically analyzed, and the design structure and manufacturing process of the sensor are given. The sensor has some advantages such as long cavity length, simple structure, simple manufacturing process, convenience and flexibility in application comparing with traditional EFPI sensor, while it can be used in the measurement of higher static pressure. Sensing demodulation system is set up to conduct a pressure test. The results show that the system has high measuring precision and good stability. Meanwhile ,the temperature sensitivity measuring experiment is conducted. Temperature sensibility coefficient is about 0.72 nm/℃ and the cavity length-temperature has good linearity. The results show that the sensor has a low temperature crossing sensitivity. In specific pressure of 0~20 MPa, pressure cavity length sensitivity of the sensor can reach 21 nm/MPa. Measuring deviation is 0.2%FS with continuous dynamic measurement of 10 h..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1010004 (2016)
Simultaneous Measurement of Temperature, Refractive Index and Liquid Level Based on Biconical Fiber Gratings
Zhao Hongxia, Chen Peihong, Ding Zhiqun, Bao Jilong, Jiang Peng, and Li Yinjie
In order to solve the problem of simultaneous multi-parameter measurement with a fiber optic sensor, we proposed a novel biconical optical fiber grating structure based on combination of the tapered optical fiber and optical fiber grating. The reflection spectral characteristics of the biconical optical fiber grating wIn order to solve the problem of simultaneous multi-parameter measurement with a fiber optic sensor, we proposed a novel biconical optical fiber grating structure based on combination of the tapered optical fiber and optical fiber grating. The reflection spectral characteristics of the biconical optical fiber grating were analyzed by using the transfer matrix method, the fundamental mode effective refractive index dispersion equation of two- and three-layer single-mode fiber and the scalar finite element method. The reflection spectrum was illustrated when the diameter of uniform erosion region was 3 μm. The hydrofluoric acid etching was used to prepare the biconical fiber Bragg grating. When the diameter of uniform erosion region was 3 μm, 12 reflection peaks including 2 primary peaks and 10 secondary peaks were observed, which is consistent with the theoretical analyses. Furthermore, three of the resonance peaks were selected to test the sensing response to temperature, refractive index and liquid level. The simultaneous detection sensitivity was found to be 9.63 nm/℃, 1975.96 nm/RIU and 26.07 nm/cm, respectively. This biconical fiber grating has a simple fabrication process, it can be used as the multiple-parameter sensors with low cost, and it can also extend the design concept of optical fiber sensor..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1010005 (2016)
Edge Filtering Demodulation and Calibration of Fiber Grating System Based on Time-Division Multiplexing
Gong Xin, Hua Dengxin, Li Shichun, Wang Jun, and Dai Chenyu
To achieve the quasi-distributed fiber grating sensing system with high spatial resolution and high measurement accuracy, the demodulation and calibration methods for the fiber grating sensing system are studied based on the time-division multiplexing technology. By combining the wavelength-division multiplexing techniTo achieve the quasi-distributed fiber grating sensing system with high spatial resolution and high measurement accuracy, the demodulation and calibration methods for the fiber grating sensing system are studied based on the time-division multiplexing technology. By combining the wavelength-division multiplexing technique with the time-division multiplexing technique, the obtained strain sensitivities of the two fiber gratings with a low reflectivity are 33.40 με/mV and 38.47 με/mV, and the non-linear error of the calibration is 2.8%. A time-division multiplexing fiber grating strain sensing system is established based on the edge filtering technique of the fiber grating spectrum. The cross-sensing demodulating algorithm of the multiplexing fiber grating strain is derived, and we test and demodulate the cross-sensing data of the two fiber gratings by experiments. The results show that the maximum error of the sensing system for a single measurement is 18 με, the relative error is less than 5% under the condition that the strain is more than 100 με, and the quoted error is less than 2% when the full scale is 600 με..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1010006 (2016)
Spectroscopy
Spectral Characteristics of Guided-Mode Resonance Filter with Wedged Waveguide Layer
Zhou Hongyan, Sheng Bin, Ni Zhengji, Huang Yuanshen, and Zhang Dawei
We designed and fabricated guided-mode resonance filters (GMRFs) with a wedged waveguide layer, and analyzed their spectral characteristics. GMRF was etched for several times with the ion-beam etching technique and a triangle-shaped mask to obtain a wedged waveguide layer. The lines of photoresist gratings and thicknesWe designed and fabricated guided-mode resonance filters (GMRFs) with a wedged waveguide layer, and analyzed their spectral characteristics. GMRF was etched for several times with the ion-beam etching technique and a triangle-shaped mask to obtain a wedged waveguide layer. The lines of photoresist gratings and thickness variation direction of the wedge-shaped waveguide layer are either parallel or perpendicular to each other. The experimental results show that the relationship between the resonance peak wavelength and position on the filter is approximately linear for the two samples. The half width at maximum in the case that the grating lines are parallel to the thickness variation direction of the wedge-shaped waveguide layer is larger than that in the case that the grating lines are perpendicular to the thickness variation direction. Through a linear gradation in the thickness of the Ta2O5 film across a distance of 20 mm, the spectral location of the reflection peaks was found to vary nearly linearly across the spectral range of 1560-1600 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 10, 1011001 (2016)
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