Journals >Chinese Journal of Lasers
Contents
2015
Volume: 42 Issue 5
48 Article(s)
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[in Chinese]
Control of Entanglement and Entropy Squeezing of the Atom Driven by a Classical Field Interacting with Field under the Dressed-State Representation
Liao Qinghong, Xu Juan, Yan Qiurong, Liu Ye, and Chen An
Using the theory of linear entropy and entropy squeezing, the dynamics of the entanglement and entropy squeezing of the atom driven by classical fields interacting with field by employing the dressed- state representation is examined. The influence of the photon number of Fock state, coupling coefficient of atoms and tUsing the theory of linear entropy and entropy squeezing, the dynamics of the entanglement and entropy squeezing of the atom driven by classical fields interacting with field by employing the dressed- state representation is examined. The influence of the photon number of Fock state, coupling coefficient of atoms and the classical driving field, and the detuning between atomic transition frequency and classical driving field frequency on the entanglement and entropy squeezing of the atom is discussed. It is shown that the evolution of linear entropy and entropy squeezing exhibits periodic behavior. The maximum value of the linear entropy increases as the photon number of Fock state, the coupling coefficient of atom and the classical driving field and the detuning increase. The high- degree squeezed and longtime atomic squeezing state can be created by controlling the coupling coefficient of atoms and the classical driving field and the detuning. The proposal may provide a theoretical way to control and manipulate the entanglement and entropy squeezing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 518001 (2015)
Research Article
Adaptive Detail Enhancement for Infrared Image Based on Subband-Decomposed Multi-Scale Retinex
Li Yi, Zhang Yunfeng, Li Ning, Fang Yanchao, Lü Chunlei, Yu Guoquan, and Chen Juan
An adaptive detail enhancement method based on subband-decomposed multi-scale Retinex is proposed to deal with high dynamic range compression of infrared images and detail enhancement in both high light regions and dim regions. Three independent spectrum subbands using subband- decomposed multi- scale Retinex are gaineAn adaptive detail enhancement method based on subband-decomposed multi-scale Retinex is proposed to deal with high dynamic range compression of infrared images and detail enhancement in both high light regions and dim regions. Three independent spectrum subbands using subband- decomposed multi- scale Retinex are gained. Then guided image filter is applied to get detail layer and base layer from each subband. Later the basis weight function for detail enhancement is proposed according to characteristic of separate spectrum subband. Adaptive detail enhancement is achieved with basis weight function. In order to eliminate the nonuniformity of gray intensity in the outcome image, a new adaptive way to get Gamma curve for gray value remapping is put forward. Experimental results show that the detail of the enhanced images is upgraded greatly in both high light regions and dim regions, and have a satisfied visual effect. Objective evaluation parameters illustrate that the proposed algorithm can effectively enhance detail of infrared images. In addition, the time consuming is not lengthened compared to other algorithms in the experiment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 512001 (2015)
Affect Analysis of Atmospheric Turbulence on Fading Characteristics in Free-Space Optical System over Different Environments
Wu Xiaojun, Wang Hongxing, Li Bifeng, and Song Bo
Optical intensity signal fading caused by the atmospheric turbulence can severely impact the performance of free space optical communication systems. Large aperture scintillometer is used to test the turbulence effect over the road and sea surface environment. Based on the obtained refractive index structure constant, Optical intensity signal fading caused by the atmospheric turbulence can severely impact the performance of free space optical communication systems. Large aperture scintillometer is used to test the turbulence effect over the road and sea surface environment. Based on the obtained refractive index structure constant, fading characteristics of free space optical communications are analyzed over these two different environments. The difference of refractive index structure constant under the road environment and the sea environment is analyzed, the result shows that the turbulence intensity of road environment is much stronger than the intensity of sea environment. The change characteristics of probability of fade of colimated Gaussian beam are studied under the two environments, when the scintillation indices are minimum, mean, and maximum, respectively. It shows that the degree of optical signal fading over road is more serious than the degree over sea environment. Fade threshold parameter is discussed when the probability of fade is 10-6..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 513001 (2015)
Atmospheric Laser Communication System Frequency-Domain Deconvolution Algorithm of Restraining Multiplicative Noise
Zhang Tong, Fan Yan, and Zhao Qian
Atmospheric turbulence will lead to the deterioration of the atmospheric laser communication link bit error rate performance. A frequency domain deconvolution method restrained multiplicative noise is proposed in the atmospheric laser communication system. The method is effective to connect the atmospheric laser communAtmospheric turbulence will lead to the deterioration of the atmospheric laser communication link bit error rate performance. A frequency domain deconvolution method restrained multiplicative noise is proposed in the atmospheric laser communication system. The method is effective to connect the atmospheric laser communication with deconvolution technology. Fast Fourier transform (FFT) module is added to the algorithm, converting the signal into frequency-domain, deconvolution filtering in the frequency-domain, reduces the algorithm complexity. Using atmospheric laser communication measurement system on a rainy day to experimental verification algorithm, contrast before and after deconvolution signal modulation constellation diagram and analyze the system bit error rate. The experimental results show that the frequency-domain deconvolution can reduce the bit error rate of atmospheric laser communication system and is a kind of effective method of multiplicative noise inhibition of atmospheric channel..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 513002 (2015)
Beam Transmission and Control
Analysis and Experimental Study on Phase-Encoded Photonic Analog-to-Digital Conversion Bsed on Phase Modulator
Li Bo, Wu Guiling, Su Feiran, and Chen Jianping
A phase-encoded photonic analog to digital conversion (PADC) based on phase modulator is presented, which can avoid the effects of the bias voltage drift and two-arm asymmetry in intensity modulator on the performance of PADC. The theoretical model of the PADC is built. The condition to realize ideal phaseencoded PADC A phase-encoded photonic analog to digital conversion (PADC) based on phase modulator is presented, which can avoid the effects of the bias voltage drift and two-arm asymmetry in intensity modulator on the performance of PADC. The theoretical model of the PADC is built. The condition to realize ideal phaseencoded PADC based on phase modulator is obtained. The effect of polarization state, amplitude and time jitter of optical sampling clock on the system performance is analyzed. The results show that the presented scheme can restrain the effect of optical sampling clock amplitude jitter, and its effective number of bits (ENOB) can be more than 10 bit in the case with reachable control precision. The feasibility and the validity of the scheme are verified by a single-wavelength system experiment with a sampling rate of 583 MS/s. The ENOB, which is 6.38 bit, is enhanced more than 2 bit by adopting phase-encoded scheme..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 505002 (2015)
Holography and Information Processing
A Method of Holographic Chromatic Aberration Compensation Based on a Liquid Lens
Wang Di, Li Fangzhuan, Wang Qionghua, and Zhou Xin
In the color holographic display, the quality of reconstructed images are affected by chromatic aberration caused by different wavelengths of color lasers. Using the zoom feature of the liquid lens, a method of holographic chromatic aberration compensation based on a liquid lens is proposed. A liquid lens using the priIn the color holographic display, the quality of reconstructed images are affected by chromatic aberration caused by different wavelengths of color lasers. Using the zoom feature of the liquid lens, a method of holographic chromatic aberration compensation based on a liquid lens is proposed. A liquid lens using the principle of electrowetting is developed. When the voltage applied to the liquid lens changes, the focal length changes accordingly. When three color lasers illuminate the corresponding holograms in turns, by keeping the focal length of the liquid lens change accordingly, three color reconstructed images can display in the same location clearly. The experimental results verify its feasibility..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 509001 (2015)
Laser Manufacturing
Study on Selective Laser Melting Forming Process of Cobalt Chromium Alloy
Liu Wei, Liu Tingting, Liao Wenhe, and Jiang Liyi
Experiments are conducted to form dental cobalt chromium alloy part with selective laser melting method. By analyzing microstructure of the specimens, effects that processing parameters of laser power, scan speed, scan space and laser energy density exert on the surface roughness, relative density and hardness of cobalExperiments are conducted to form dental cobalt chromium alloy part with selective laser melting method. By analyzing microstructure of the specimens, effects that processing parameters of laser power, scan speed, scan space and laser energy density exert on the surface roughness, relative density and hardness of cobalt chromium are studied. Research results show that different laser power, scan speed and spacing lead to different surface roughness although the laser energy density remains the same. Relative density of SLM cobalt- chromium alloy increases as the laser power increases and the rate of change slows down. When scanning speed varies from 80 mm/s to 100 mm/s, maximum value of SLM CoCr part reaches 94.95% . With the increase of laser scanning space, the relative density reduces. Besides, with laser power varying from 50 W to 100 W, net- shaped grain size increases from 0.8 mm to 2 mm, while higher laser power will cause much bigger grain size and decrease the Vickers hardness. The average hardness of SLM CoCr part is 392 HV, slightly higher than the standard value within a reasonable range..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 503001 (2015)
Impact of Hollow Ring Laser Defocused Amount on Melting Channel Bump Defect Self Healing Effect
Yang Shi, Shi Shihong, Fu Geyan, Shi Jianjun, Meng Weidong, and Wang Tao
“Morphology self healing effect”is an important phenomenon that may happen in the direct laser melt forming process, which can adjust the process parameters of itself and control the multi- level melting channel accumulation surface from a bump unstable state to a stable state in the process of accumulation. By adoptin“Morphology self healing effect”is an important phenomenon that may happen in the direct laser melt forming process, which can adjust the process parameters of itself and control the multi- level melting channel accumulation surface from a bump unstable state to a stable state in the process of accumulation. By adopting the new process of“hollow laser, internal laser powder feeding”, adjusting the ring laser defocused amount can effectively result in self healing effect of melting channel bump defect. The impact of laser defocused amount on monolayer thickness accumulation is theoretically analyzed and resulted in a curved diagram between laser defocused amount and monolayer thickness accumulation and it has been tested as accumulate multiple thin wall samples in 304 stainless steel substrate with“fence bulge”. At the same time, the thin wall width, microstructure and thickness have been analyzed by venire caliper, scanning electron microscope and micro hardness instrument. The study has shown that there is a significant impact of different laser defocused amounts on the self healing capabilities. When the defocused amount is 0~-3 mm, the surface topography of the thin wall is undulating, and“the self healing phenomenon”has not been shown. While the defocused amount is -3 mm~-5 mm, the thin wall undulating surface will become smooth gradually in several levels, and the“self healing phenomenon”has been verified. The thin wall by self healing repair combines well with the substrate metallurgy and the width slightly changing. The structure is dense and uniform, and the hardness value from the wall top to the substrate increases slowly..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 503002 (2015)
Experimental Study of Ti/Al Impact Spot Welding by Intense Laser Pulse Induced Shock Waves
Gu Yuxuan, Wang Xiao, Shen Zongbao, Qiu Tangbiao, Ma Youjuan, Zhang Di, and Liu Huixia
A novel laser impact spot welding process is proposed, during which solid state and metallurgical bonding of similar or dissimilar metal combinations can be obtained. In the experiment, the laser pulse is launched from a Nd∶YAG laser to induce the Ti foil in the thickness of 30 μm to bulge and collide to the 100 μm thiA novel laser impact spot welding process is proposed, during which solid state and metallurgical bonding of similar or dissimilar metal combinations can be obtained. In the experiment, the laser pulse is launched from a Nd∶YAG laser to induce the Ti foil in the thickness of 30 μm to bulge and collide to the 100 μm thickness Al plate with high speed to get spot joint. When the standoff distances of the Ti foil are 0.3、0.6、0.9 mm, respectively, the springback area at the center of the weld spot decreases, and the bonding area increases gradually. The cold inlaid technique is used to fix the weld examples for studying the cross-sections features of the weld spot, and wavy interface with the alterative amplitude and period along the diameter direction of the weld spot and the straight weld interface are observed. In order to investigate the influence of laser impact spot welding on the mechanical properties of the materials in the weld zone, the nanoindentation hardness test is applied across the weld interface. It is found that the microhardness in the weld interface region increases obviously. Moreover, the results lap shear strength test show the bonding strength of weld spot is relatively fine when effective solid-state and metallurgical bond is obtained during welding, and the failure usually occurs at the edge of the weld spots. Laser impact spot welding provides a new way for dissimilar metal foils welding in the thickness of micro level..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 503003 (2015)
Effect of Sn-5%Zr Powder Addition on Microstructure and Mechanical Property of Steel/Al Laser Welding
Zhou Dianwu, Liu Yuanli, Li Ningning, Xu Shaohua, and Liu Jinshui
The laser welding test with Sn-5%Zr (mass fraction) powder addition is carried out on the DP590 dual phase steel with thickness of 1.4 mm and the 6016 aluminum alloy with thickness of 1.2 mm. By using optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), electron backscatter diffraction (EBCDThe laser welding test with Sn-5%Zr (mass fraction) powder addition is carried out on the DP590 dual phase steel with thickness of 1.4 mm and the 6016 aluminum alloy with thickness of 1.2 mm. By using optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), electron backscatter diffraction (EBCD) and tensile test, the effect of Sn-5%Zr powder addition on the microstructure, fracture morphology, main phase, content and distribution of phase, grain size and mechanical properties of joints are studied. Elastic moduli are calculated by using first-principle method based on density functional theory for FeSn, Fe3Sn, Fe3Al, FeAl and Fe2Al5 compounds. The results indicate that the average shear strength of the welding sample with Sn- 5% Zr powder reaches 37.90 MPa. Compared with that without Sn-5%Zr powder addition,the average shear strength of welded joint increases. Because of the formation of ZrAl3 compounds, it promotes the refined grain size of Fe- Al intermetallic compound in aluminum/steel interface, Al spreads to the molten pool is inhibited by Sn, the thickness of Fe-Al intermetallic compound layer is reduced, FeSn and Fe3Sn intermetallic compounds have better ductility, the proportion to brittleness and ductility phases of the interface layer Fe-Al intermetallic compounds are changed, the weld width and bonding rate effectively increased, which can improve the mechanical properties of weld joint with Sn-5%Zr powder addition..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 503004 (2015)
Research of Effects with Al-Si Coating on Distribution and Performance of Tailored Laser
Zhang Fan, Li Fang, Hua Xueming, Wang Shien, Wang Daming, and Chu Weidong
The metallographic phases and tensile strength of tailored fiber laser welded blanks of Al-Si coated Usibor1500 and Usibor1500 without coating are investigated, and the distribution of Al in the weld seams is investigated by energy- dispersive X- ray spectroscopy (EDS). Ambient tensile strength is tested to study the dThe metallographic phases and tensile strength of tailored fiber laser welded blanks of Al-Si coated Usibor1500 and Usibor1500 without coating are investigated, and the distribution of Al in the weld seams is investigated by energy- dispersive X- ray spectroscopy (EDS). Ambient tensile strength is tested to study the difference with or without top coating layer. The results show that, Al enters the weld seam and distributes in the whole area of weld seam and be with local segregation, the mass percent of Al in two phases are 1.76% and 2.65% , respectively. Al- Si coating which entering the weld seam decreases the mechanical properties of weld seam due to the formation of brittle phase, whose strength is 458~479 MPa, while the strength of base metal is around 500 MPa. After removing the top layer of the coating, the mechanical properties increase distinctly, whose fracture locations are consistently at the base metal..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 503005 (2015)
Numerical Simulation of Temperature Field Evolution in the Process of Laser Metal Deposition
Zhang Dongyun, Wu Rui, Zhang Huifeng, and Liu Zhen
A comprehensive three-dimensional transient model is developed for the evolution of the temperature field during the vertical wall manufacturing process using coaxial laser metal deposition (LMD), the material manufactured is directional solidification (DS) superalloy Rene80. The interaction between laser and powder duA comprehensive three-dimensional transient model is developed for the evolution of the temperature field during the vertical wall manufacturing process using coaxial laser metal deposition (LMD), the material manufactured is directional solidification (DS) superalloy Rene80. The interaction between laser and powder during the powder falling process is simulated, and its possible effect on the temperature field of molten pool is analyzed. After that, the evolution of temperature field during the vertical wall manufacturing process is studied. By numerical simulation, the change of phase (solid/liquid, and mushy zone) and the liquid flowing are considered and the parameters are from optimized vertical wall manufacturing experiments. The results reproduce the shape changing of the molten pool and the instability of laser metal deposition process. The changing rule of temperature field is in conformity with that of real vertical wall manufacturing experiment..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 503006 (2015)
Experimental Research on Size Effects in Laser Dynamic Flexible Micro-Bending Forming
Ma Youjuan, Liu Huixia, Zhou Jianzhong, Zhu hejun, Chen Jun, Qian Qing, and Wang Xiao
After the preparation of the multi-feature micro-bending mold, the isobaric micro-bending of foil plate can be achieved by laser dynamic flexible microforming under single pulse. In order to investigate the workpiece size (thickness) and grain size effects on high strain rate deformation behavior of foil plate, the digAfter the preparation of the multi-feature micro-bending mold, the isobaric micro-bending of foil plate can be achieved by laser dynamic flexible microforming under single pulse. In order to investigate the workpiece size (thickness) and grain size effects on high strain rate deformation behavior of foil plate, the digital microscopic is used to observe the surface topography of formed parts. Besides, Triboindenter nanomechanical test instrument is employed to obtain the micro-hardness distribution along thickness direction. With the aid of cold mosaic technique, the thinning rate of thickness is measured. Experimental results show that the contour of formed parts change from dome shape to groove shape when the thickness decreases from 50 μm to 30 μm due to the reduced flow stress of copper foil. After the strong impact with the bottom of micro-mold, the groove-like parts rebound and the micro-hardness of parts is improved significantly. Compared with the fine-grained formed parts, the forming ability is rather poor with the uneven rebound deformation and strain hardening across thickness direction. The maximum thinning rate of coarse-grained parts has an increase of approximately 10% than the fine-grained ones, which means the fillet region is easier to rupture..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 503007 (2015)
Comparative Research of Stellite 6 Coatings Prepared by Supersonic Laser Deposition and Laser Cladding
Li Zhihong, Yang Lijing, Zhang Qunli, Li Bo, and Yao Jianhua
Supersonic laser deposition (SLD) is a new coating and fabrication process in which a supersonic powder stream produced by cold spray (CS) impinges on a substrate simultaneously heated by laser irradiation. Due to laser heating, the range of materials deposited in SLD process can be expanded to higher strength materialSupersonic laser deposition (SLD) is a new coating and fabrication process in which a supersonic powder stream produced by cold spray (CS) impinges on a substrate simultaneously heated by laser irradiation. Due to laser heating, the range of materials deposited in SLD process can be expanded to higher strength materials which are usually hard or even impossible to be deposited solely by CS. Stellite 6 coating prepared by SLD and laser cladding (LC) are studied and compared in terms of macro- morphology, microstructure, interface dilution and micro- hardness. The results show that the original nature of the impacting particles remains in the SLD Stellite 6 coating, and its microstructure is different from the coarse dendritic microstructure of LC Stellite 6 coating. The dilution rate of LC coating is about 12% , while no macroscopic dilution zone is found in supersonic laser deposition coating. The heat- affected zone of supersonic laser deposition shrinks compared with that of LC. The average microhardness of Stellite 6 coating produced by SLD is 694 HV0.2, which is 1.45 times higher than that of LC Stellite 6 coating..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 503008 (2015)
Study of Stresses of Laser Metal Deposition Using FEM Considering Phase Transformation Effects
Fang Jinxiang, Dong Shiyun, Xu Binshi, Wang Yujiang, He Peng, Xia Dan, Zhang Zhihui, and Ren Weibin
To investigate the influences of solid state phase transformation on stress evolution during laser matal powder deposition, a 3D finite-element thermo-mechanical model considering phase transformation effects is established. The stress fields during single layer and multiple layer laser metal deposition process are anaTo investigate the influences of solid state phase transformation on stress evolution during laser matal powder deposition, a 3D finite-element thermo-mechanical model considering phase transformation effects is established. The stress fields during single layer and multiple layer laser metal deposition process are analyzed. Stress measurement of blind hole method is applied to cladded samples. The results are compared with the computational predictions, which should be a validation for the predictions with the inclusion of transformation kinetics. The importance of considering phase transformation effects is verified through the comparison of the magnitudes of residual stresses with and without the inclusion of transformation kinetics..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 503009 (2015)
Experimental Study of Laser Transmission Welding between Polycarbonate and Polyphenylene Oxide
Wu Yanwei, Liu Huixia, Li Pin, Cai Ye, Fan Cailian, Meng Dongdong, Qiu Tangbiao, and Wang Xiao
Laser transmission welding properties between two dissimilar polymers- polycarbonate and polyphenylene oxide are studied. The influence of temperature properties and compatibility on the weld ability are investigated. Diode laser and tensile machine are used for the welding and tensile-shear test respectively. The procLaser transmission welding properties between two dissimilar polymers- polycarbonate and polyphenylene oxide are studied. The influence of temperature properties and compatibility on the weld ability are investigated. Diode laser and tensile machine are used for the welding and tensile-shear test respectively. The process parameters are designed and optimized through response surface methodology. Failure forms of weld joint under different scanning velocities are investigated by observing the fracture morphology through a 3D microscope. The results show that under the condition of 6.34 W power, 40 mm/s scanning velocity, 0.39 MPa clamp pressure, the best tensile-shear strength is 6.51 MPa. The compatibility between two melting polymers and the welding defects (ablation and voids) are the major factors that determine the mechanical properties and failure form of the joints. Dissimilar polymers are weldable by laser transmission welding..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 503010 (2015)
Laser Physics
Evaluating Specifications of Laser Beam Quality Based on Beam Profile
Li Xiaoming, Shen Xueju, Li Gang, and Liu Xun
A simple evaluation method of laser beam quality used out of laboratory is proposed. Through detecting profiles of laser spots, laser beam quality is measured. According to the principles, a suite of parameters are defined to express beam quality, what is more, the measured schemes and algorithms are shown. The relatioA simple evaluation method of laser beam quality used out of laboratory is proposed. Through detecting profiles of laser spots, laser beam quality is measured. According to the principles, a suite of parameters are defined to express beam quality, what is more, the measured schemes and algorithms are shown. The relationship between output energy and misalignment is researched in both mirror slanting and change of Q-states based on electro-optic Q-switch pulse laser pumped by lamp. Experimental results show that new parameters increase with the increase of misalignment and average value of parameter difference on adjacent two sections can be used to evaluate beam quality in large amount of disorder. These results indicate that valuating specifications presented can be used to evaluate beam quality and only light-sensitive photographic paper, digital camera and calculation procedure are used in the process. For simple measuring method and low experiment condition requirement, it can be used in preliminary detection of laser working position out of laboratory..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 502001 (2015)
Analysis of Laser Thermal-Mechanical Effect on Morphology of Electrochemical Etching on Various Materials
Zhang Zhaoyang, Feng Qinyu, Zhou Jianzhong, Cai Mingxia, Gao Xing, and Wu Shengquan
In the established nanosecond pulse laser electrochemical machining (LECM) system, a compound processing method of laser and electrochemistry is used to process metals such as 304 stainless steel, 7075 aluminium alloy, 1060 aluminium and brittle materials like silicon under the same processing parameters. The mechanismIn the established nanosecond pulse laser electrochemical machining (LECM) system, a compound processing method of laser and electrochemistry is used to process metals such as 304 stainless steel, 7075 aluminium alloy, 1060 aluminium and brittle materials like silicon under the same processing parameters. The mechanism of the laser thermal- mechanical effect on promoting electrochemical machining is investigated. The polarization curves of different materials are measured. The compound processing surface morphologies of different materials are comparatively analyzed by scanning electron microscope (SEM). A VHX- 1000 threedimensional super depth digital microscope is adopted to analyze the processing depths, widths and aspect ratios of different materials. The results indicate that under the action of laser thermal- mechanical effect, the electrochemical etching quality and surface morphology of aluminum alloy are better than those of stainless steel and aluminum. And relatively large aspect ratio microstructure can be processed. Besides, the shock calving of microparticle occurs to the brittle materials..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 502002 (2015)
Designing and Testing of Tunable DFB Laser Array Using REC Technology
Ni Yi, Zhang Jie, and Kong Xuan
Design of wavelength control of a tunable laser with the wavelength tunable range from 1310 nm to 1319 nm is introduced and its feasibility is verified by experimental tests. The laser chip adopted by this system is distributed feedback (DFB) laser array based on reconstruction-equivalent-chirp (REC) technology and theDesign of wavelength control of a tunable laser with the wavelength tunable range from 1310 nm to 1319 nm is introduced and its feasibility is verified by experimental tests. The laser chip adopted by this system is distributed feedback (DFB) laser array based on reconstruction-equivalent-chirp (REC) technology and the realization of wavelength tunning is based on the interaction between the upper computer [personal computer, (PC)] and lower computer [micro controller unit, (MCU)]. The results demonstrate that this system applied to dense wavelength division multiplexing (DWDM) in 50 GHz spacing at 1310 nm can keep the wavelength accuracy within the range of 0.01 nm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 502003 (2015)
Four-Wavelength Near & Mid-Infrared Optical Parameter Oscillator Based on Superlattice
Zhao Gang, Jiang Xudong, Lv Xinjie, and Qin Yiqiang
Four-wavelength near&mid-infrared laser (1568.4, 1625.9, 3078.8、3231.1 nm) based on stoichiometric LiTaO3 superlattice (PPSLT) crystal is reported. The pump source is an optical fiber laser at 1064 nm wavelength. PPSLT has a dual-channels grating of 30 mm and 30.5 mm. When the pump power is 37 W, and repetition freFour-wavelength near&mid-infrared laser (1568.4, 1625.9, 3078.8、3231.1 nm) based on stoichiometric LiTaO3 superlattice (PPSLT) crystal is reported. The pump source is an optical fiber laser at 1064 nm wavelength. PPSLT has a dual-channels grating of 30 mm and 30.5 mm. When the pump power is 37 W, and repetition frequency is 50 kHz, the total output power reaches 14.9 W. The powers of the four wavelength lasers are 3.71, 4.36, 3.21 and 3.62 W, respectively. By adjusting the temperature of the PPSLT crystal, tunable output can be realized. Further optimization of optical parameter oscillator (OPO) resonant cavity will realize the equivalent output power of the four wavelength lasers..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 502004 (2015)
Study on Seam Tracking System Based on Stripe Type Laser Sensor and Welding Robot
Li Lin, Lin Bingqiang, and Zou Yanbiao
A new seam-tracking system based on stripe type laser sensor and welding robot is proposed. The laser sensor is fixed to the end of the robot. The weld propfile data is abstracted in real- time during the welding process. And the wavelet transform modulus maxima theory is used to extract the welding characteristic- poiA new seam-tracking system based on stripe type laser sensor and welding robot is proposed. The laser sensor is fixed to the end of the robot. The weld propfile data is abstracted in real- time during the welding process. And the wavelet transform modulus maxima theory is used to extract the welding characteristic- points. The contour data is grouped based on the characteristic- points. And then, the least square method is used to fit the weld lines and calculate the intersection point of straight line, which is aimed to determine the coordinates of the characteristic- points accurately. At last, the coordinate transformation calculation is used to get the trajectory of the welding torch in real-time. Then, two experimental verifications for different V- shape welds are carried on. Comparing experiments between only using wavelet transform modulus maxima theory and using wavelet transform modulus maxima and the least square method are performed. The experimental results show that the error of the former is about 0.514 mm, but the trajectory exists serious jitter phenomenon. The error of the other is about 0.304 mm and the jitter phenomenon significantly diminishes, which satisfies the requirements of automatic welding of requirements within 0.5 mm..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 502005 (2015)
20 kHz Narrow Linewidth Fiber Bragg Grating External Cavity Semiconductor Laser
Pan Biwei, Yu Liqiang, Lu Dan, Li Linsen, Zhang Limeng, Li Zhaosong, Su Hui, and Zhao Lingjuan
A buried ridge stripe (BRS) gain chip integrated with a fiber Bragg grating external cavity is fabricated for stable, single mode narrow-linewidth semiconductor laser with wavelength of 1.5 μm. The laser can realize single longitudinal mode output with the side-mode suppression ratio over 40 dB in the bias current tuniA buried ridge stripe (BRS) gain chip integrated with a fiber Bragg grating external cavity is fabricated for stable, single mode narrow-linewidth semiconductor laser with wavelength of 1.5 μm. The laser can realize single longitudinal mode output with the side-mode suppression ratio over 40 dB in the bias current tuning from 30 mA to 250 mA. The largest output power from fiber pigtail is larger than 10 mW. In the current tuning range, the linewidth is below 15.48 kHz and a minimum linewidth of 6.75 kHz is achieved. By using the beating-frequency method, the measured frequency fluctuation is 7.2×10-8/s. This compact and low cost narrow linewidth laser can be used as the optical source and the local oscillation source in the future 400 Gb/s communication systems..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 502007 (2015)
10 W-Level High Efficiency Single-Mode Mid-Infrared 2.8 μm Fiber Laser
Shen Yanlong, Huang Ke, Zhou Songqing, Luan Kunpeng, Zhu Feng, Chen Hongwei, Yu Li, Yi Aiping, Feng Guobin, and Ye Xisheng
A high power and high efficiency mid-infrared at 2.8 μm single mode fiber laser is demonstrated. Output power of exceeding 9 W from heavily Er3 +-doped ZBLAN double-clad fiber pumped by a laser-diode (LD) centered at 975 nm is obtained in continuous wave regime. The experimental results indicate that the maximum outputA high power and high efficiency mid-infrared at 2.8 μm single mode fiber laser is demonstrated. Output power of exceeding 9 W from heavily Er3 +-doped ZBLAN double-clad fiber pumped by a laser-diode (LD) centered at 975 nm is obtained in continuous wave regime. The experimental results indicate that the maximum output power of the fiber laser is 9.2 W corresponding to the slope efficiency of 24.8%. Moreover, the threshold and the center wavelength are around 1.0 W and 2.79 μm, respectively. The fiber laser is in single mode operation, with beam quality factor M2 of less than 1.2..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 502008 (2015)
Homogenization System for Diode Laser Stack Beams Based on Microlens Array
Lei Chengqiang, Wang Yuefeng, Yin Zhiyong, Yin Shaoyun, and Sun Xiuhui
The intensity distribution of diode laser is not uniform due to the broad-area and ridge-waveguide designs, the poor beam quality is the limiting factor of applications. In order to achieve homogenized spot by the beam shaping of high-power diode laser stack, a homogenization system for diode laser stack beams based onThe intensity distribution of diode laser is not uniform due to the broad-area and ridge-waveguide designs, the poor beam quality is the limiting factor of applications. In order to achieve homogenized spot by the beam shaping of high-power diode laser stack, a homogenization system for diode laser stack beams based on microlens array is designed. The diode laser beam shaping theory and process of microlens array are analyzed. The lower limit of clear aperture of microlens is confirmed by the analysis of the impact of the diffraction of microlens edge on the spot homogeneity. The intensity angle distribution of spot is defined by paraxial matrix optical analysis. The simulation and experimental test are carried out for the microlens array beam shaping system, realizing the spot with the homogeneity of 91.89%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 502009 (2015)
Research on Focus Zooming by Oscillator XeCl Excimer Laser
Zhu Yongxiang, Zhao Xueqing, Hu Yun, Wang Dahui, and Zhang Yongsheng
In direct-drive laser fusion, the laser-target coupling efficiency can be enhanced and therefore the necessary driving laser energy can be reduced if the laser spot is zoomed with the target during implosion. A focal zooming is realized by image relay, in which the laser pulse is separated and split by the prism in an In direct-drive laser fusion, the laser-target coupling efficiency can be enhanced and therefore the necessary driving laser energy can be reduced if the laser spot is zoomed with the target during implosion. A focal zooming is realized by image relay, in which the laser pulse is separated and split by the prism in an optical swithch. By this scheme, the laser energy would not be wasted and that some multiple splitting ways and pulse shaping become possible. A three- stage focus zooming system of XeCl laser is established and the zooming process is recorded by a streak camera. The experimental results suggest that the edge gradient between the stages is determined by that of the driving pulse for the Pockels cell in the switch..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 502010 (2015)
Materials and Thin Films
Effect of Laser Shock on the Electrical Property of ZnO-Based Ceramic Films
Hua Yinqun, Ji Ping, Chen Ruifang, and Zhao Shanyue
ZnO-based ceramic films are deposited on Si (111) substrates by radio frequency magnetron sputtering technique, and the films are shocked by the Nd∶YAG laser. The effect of laser shock on the electrical property of ZnO-based ceramic films is investigated. The results show that after laser shock processing, the films′ gZnO-based ceramic films are deposited on Si (111) substrates by radio frequency magnetron sputtering technique, and the films are shocked by the Nd∶YAG laser. The effect of laser shock on the electrical property of ZnO-based ceramic films is investigated. The results show that after laser shock processing, the films′ grain size is reduced significantly and the surface are more smooth and compact. The electrical properties of films have been improved in varying degrees. The nonlinear coefficient is largest raised by 65.2%，the breakdown voltage is largest decreased by 38.92%, the leakage current density is largest decreased by 24.4%. After the laser shock processing, with the grain refinement and lattice distortion, the interface-state density is sharply increased, which leads to the improvement of the nonlinear coefficient. Therefore the electrical property of ZnO-based ceramic films is excellent..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 507001 (2015)
Measurement and Metrology
Wavefront Testing Based on Broadband Phase Diversity Technology
Cheng Qiang, and Xue Donglin
The basic principles of wavefront sensing based on phase diversity (PD) are introduced. And the phase diversity is extended from monochromatic or quasi- monochromatic light illumination to broadband spectrum light illumination. Based on lots of computer simulation and analysis, the validation experiment of broadband PDThe basic principles of wavefront sensing based on phase diversity (PD) are introduced. And the phase diversity is extended from monochromatic or quasi- monochromatic light illumination to broadband spectrum light illumination. Based on lots of computer simulation and analysis, the validation experiment of broadband PD technology is designed. The integrating sphere is used as the light source, and the modulation transfer function (MTF) testing experiment of some optical system is established in the lab. The wavefront of optical system and the best position of focal plane are calculated by broadband PD technology, and the images collected are restored. Furthermore, the outfield imaging experiment is designed. The broadband PD is applied to solve the wavefront aberration according to the images collected. The result shows that the difference between wavefront aberration solved by broadband PD and the root mean square (RMS) of interferometric testing result is less than 0.03λ, and the difference of focal plane position solved by PD and MTF testing is less than 0.03 mm. The testing precision of broadband PD satisfies the requirement of engineering..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 508001 (2015)
Numerical Simulation of Laser Ultrasonic Elastic Constant Measurement Based on Abaqus
Zhan Yu, Xue Junchuan, and Liu Changsheng
The mechanical properties of the material directly affects the safety and life of the components, and the elastic constants of materials is an important index of its mechanical properties. The finite element software Abaqus is used to simulate the propagation of Rayleigh surface wave and longitudinal wave laser excitatThe mechanical properties of the material directly affects the safety and life of the components, and the elastic constants of materials is an important index of its mechanical properties. The finite element software Abaqus is used to simulate the propagation of Rayleigh surface wave and longitudinal wave laser excitation in the dissemination process of sheet metal sample surface and in vivo. Effect of pulse laser on the sample used is equivalent to the modified Gauss distribution power source to generate the ultrasonic. The infinite element at the boundary is set to eliminate the interference signal echo, and receive the ultrasonic signals to calculate the velocity of Rayleigh surface wave and longitudinal wave. According to the relationship between velocity and elastic constants, elastic constants is detected. The numerical results are in good agreement with theoretical solution, thus a very effective numerical method for laser ultrasonic detection of elastic constants of materials to provide..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 508002 (2015)
Research of Peak Count Rate Scanning Method for Single Photon Detector Used in High Precision Optical Transfer Time Measurement
Zeng Zhilong, Zhu Yong, Lu Lin, Zhang Baofu, Wu Chuanxin, and Wei Yimei
A new method to measure transfer time delay in optic fiber more accurately is proposed to deal with timing jitter of single photon avalanche detector worked in Geiger mode. The arrival time of echo optical signal is determinated by adjusting the arrival time and width of gate signal to make the photon count rate reach A new method to measure transfer time delay in optic fiber more accurately is proposed to deal with timing jitter of single photon avalanche detector worked in Geiger mode. The arrival time of echo optical signal is determinated by adjusting the arrival time and width of gate signal to make the photon count rate reach the maxim value. The method avoids the intrinsic timing jitter of single photon avalanche detector. After deliberately theory analysis, system experiment is performed in fiber of length approximate 125 km, the experiment shows that measurement precision is about 35 ps and the accuracy is about 13 ps..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 508003 (2015)
Phase Extraction Method of Microsphere Interferometry Based on Error Complementary Correction
Lu Binghui, Liu Guodong, Sun Heyi, Liu Bingguo, and Chen Fengdong
In order to measure the surface topography of microsphere with phase-shifting interferometer in high precision, phase extraction method is of great important. But there is always linear phase shifting error existence coming from system calibration error or defocus, which influences the phase extracting accuracy. The coIn order to measure the surface topography of microsphere with phase-shifting interferometer in high precision, phase extraction method is of great important. But there is always linear phase shifting error existence coming from system calibration error or defocus, which influences the phase extracting accuracy. The common phase shifting algorithms are not quite suitable for the measurement of sphere, especially when the linear error is larger, so a new five frames algorithm is constructed. The response characteristics of new algorithm is much close to Hariharan algorithm, but is opposite in sign. Therefore, by the complementray correction of the two algorithms, the phase calculation error is reduced by two orders of magnitude. The capacity of fixed-step algorithm for linear phase shifting error control is improved greatly and there is no abnormal phase result coming out, which always appears in the calculation process by any equal step algotithm. The algorithm based on phase error complementary correction is much more compact for calculations, its feasibility and effectiveness are proved by the actual measurement experiment of a microsphere..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 508004 (2015)
Improving transmission performance of optical resonator by thermal oxidation
Li Minghui, Luo Liang, Ma Kezhen, Qiu Haitao, Xue Chenyang, Zhang Wendong, and Yan Shubin
For improving the larger sidewall roughness of an optical waveguide and exploring the advantages of fractionated oxidation over a single oxidation process, silicon-on-insulator ring and racetrack cavities are prepared using microelectro-mechanical system (MEMS) technology. The silicon-on-insulator ring and racetrack caFor improving the larger sidewall roughness of an optical waveguide and exploring the advantages of fractionated oxidation over a single oxidation process, silicon-on-insulator ring and racetrack cavities are prepared using microelectro-mechanical system (MEMS) technology. The silicon-on-insulator ring and racetrack cavities are optimized by single and double oxidation processes, respectively. The relationships among the roughness, scattering loss, and transmission characteristics of an optical resonator are theoretically analyzed and simulated. The experimental results show that, a narrower full-width at half-maximum (FWHM), higher quality factor (Q), and lower transmission loss are achieved by the double oxidation process, compared with those achieved by the single oxidation process, for the same oxidation thickness. This result provides a reference for surface-smoothing research and has a significant influence on the preparation and application of cavities with high Q and low transmission loss in filters, biosensors, optical gyroscopes, and other related fields..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 508005 (2015)
A New Calibration Method for Fisheye Lens Based on Spherical Model
Wu Zejun, Wu Qingyang, and Zhang Baichun
A new calibration method based on the spherical model for fisheye lens using two- dimensionally calibration target is presented. According to the relationship between the point on arc and the image points for the spherical model, the internal parameters by the points in a straight line on the plane target are preliminaA new calibration method based on the spherical model for fisheye lens using two- dimensionally calibration target is presented. According to the relationship between the point on arc and the image points for the spherical model, the internal parameters by the points in a straight line on the plane target are preliminary estimate. And the corresponding external parameters by the mapping between the world points and the points in arc on the sphere are calculated. The rooy- mean- square error of the image points and the reprojection points are taken as the optimization parameter and the exact solution of the internal parameters, the distortion coefficients and the external parameters are solved by the nonlinear optimization algorithm. The experiment presents that the proposed method can quickly estimate the initial values of the internal and external parameters for the fisheye lens with high-precision and meet the practical applications..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 508006 (2015)
Research on Geometric Parameter Measurement Method Using Laser Tracker in Null Lens Asphere Testing
Chen Xindong, and Li Ruigang
Traditional measuring methods of geometric parameters of asphere cannot meet the accuracy requirements as the aperture and vertex radius of curvature increase. In order to realize high accuracy measurement of geometric parameters, analysis and measuring methods are studied according to the null lens testing. The theoreTraditional measuring methods of geometric parameters of asphere cannot meet the accuracy requirements as the aperture and vertex radius of curvature increase. In order to realize high accuracy measurement of geometric parameters, analysis and measuring methods are studied according to the null lens testing. The theoretical relationship between radius error and conic constant error is compared with the simulation results, then the requirements of measurement and data processing check method are determined. The basic principles of using laser tracker to measure geometric parameters are presented. The feature transformation, modeling and data processing methods are introduced. Experimental results show that the repeating precision of radius, conic constant and off-axis distance are ±0.039 mm, ±2.05×10-5 and ±0.055 mm, respectively. The high repeating accuracy indicates that this method is suitable for geometric parameters measurements, especially for large aperture and long radius aspheres. The absolute accuracy needs to be further analyzed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 508007 (2015)
Research on Texture Characteristics Analysis of Ancient Glaze Optical Coherence Tomographic Image
Yan Xin, Dong Junqing, Liu Weidong, and Li Qinghui
In order to quantify the structural characteristics of ancient porcelain glazes, seven texture characteristic parameters, which are used to describe the optical coherence tomographic (OCT) images of four typical plain enamel samples, are extracted based on image histogram and gray level co-occurrence matrix. The differIn order to quantify the structural characteristics of ancient porcelain glazes, seven texture characteristic parameters, which are used to describe the optical coherence tomographic (OCT) images of four typical plain enamel samples, are extracted based on image histogram and gray level co-occurrence matrix. The differences between the seven texture characteristic parameters of four kinds of glazes are obvious. The feasibility of glaze recognition scheme based on K-neighbor classification and quantitative analysis of texture feature parameters is certified by using an unknown sample. Experimental results show that seven characteristic parameters can characterize the glaze layer structure characteristics commendably. The glaze recognition scheme based on Kneighbor classification and quantitative analysis of texture feature parameters is feasible and promising..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 508008 (2015)
Optical Communication
Design and Implementation of Multi-Channel Photonic Time-Stretch Analog-to-Digital Converter
Qian Aquan, Zou Weiwen, Wu Guiling, and Chen Jianping
Photonic time-stretch analog-to-digital converter (PTS-ADC) system utilizes the dispersion effect of fibers to stretch the sampled analog signal in time domain and compress its bandwidth in frequency domain, which can highly improve the sampling rate and bandwidth of the traditional analog-to-digital converter (ADC). DPhotonic time-stretch analog-to-digital converter (PTS-ADC) system utilizes the dispersion effect of fibers to stretch the sampled analog signal in time domain and compress its bandwidth in frequency domain, which can highly improve the sampling rate and bandwidth of the traditional analog-to-digital converter (ADC). Due to the time-aperture limitation, the traditional PTS-ADC is difficult to satisfy the continuous-time signal sampling. Multi-channel architecture is adopted to achieve a PTS-ADC operating in the continuous-time mode. However, this architecture introduces the inter-channel mismatch. A multi-channel architecture is optimized so as to achieve a continuous-time PTS-ADC system with improved accuracy. The effects of inter-channel offset, gain and time mismatches are studied by numerical simulation. A three-channel experimental system with the sampling rate of more than 200 GSa/s, bandwidth of 45 GHz, and effective number of bits (ENOB) of ~3.7 is domonstrated..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 505001 (2015)
Investigation on the Characteristics of Photonic Crystal Channel Drop Filter
Wu Liheng, and Wang Minghong
In order to make different frequency bands propagate along their own channels, three typical structures of channel drop filter (CDF) are designed in a 2-dimension dielectric rod square photonic crystal structure. Their performance characteristics are investigated by the finite-difference time-domain method， and transmiIn order to make different frequency bands propagate along their own channels, three typical structures of channel drop filter (CDF) are designed in a 2-dimension dielectric rod square photonic crystal structure. Their performance characteristics are investigated by the finite-difference time-domain method， and transmission efficiency graphs of the their output ports are obtained. The maximal transmission power ratio of every channel is at a central frequency of pass-band, and the power ratios will decay swiftly when the frequency shifts towards higher or lower than the central one. These structures of CDF have the characteristics of excellent frequency selectivity, weak crosstalk among central frequencies of different bands, broad operating wavelength ranges, etc. They can be used to design micro devices such as narrow band-pass filter or band-stop filter. Therefore, the CDF has important application value in the design of optical path on a photonic crystal chip and wavelength division multiplexed optical communication systems, etc..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 505003 (2015)
Optical Vortex Soliton in Parity-Time Symmetric Potentials
Zhou Bozhen, Hua Chunbo, Xu Siliu, and Lv Peng
A theoretical model of optical singular soliton in periodic parity-time (PT) symmetric potentials without defects and non-periodic PT symmetric potentials with positive and negative defects is introduced. Based on variational method, the width and potential energy of soliton in PT symmetric potentials without defects aA theoretical model of optical singular soliton in periodic parity-time (PT) symmetric potentials without defects and non-periodic PT symmetric potentials with positive and negative defects is introduced. Based on variational method, the width and potential energy of soliton in PT symmetric potentials without defects are analysed. The range of linear stability of soliton is also researched by linear stability analysis. It is shown that singular soliton can stably transmitte in the PT symmetric potentials under some appropriate parameters..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 505004 (2015)
Investigation of the Pump Schemes in Photonics Crystal Fiber Femtosecond Laser Amplifier
Zhao Xiaowei, Chai Lu, Shi Junkai, Liu Bowen, Hu Minglie, Li Yanfeng, and Wang Qingyue
Numerical simulation results and experimental verification on the pulse evolution process in a photonics crystal fiber (PCF) femtosecond laser amplifier with different pump schemes are reported. A model combining rate equations with nonlinear Schrodinger equation, which considers the interaction among non-uniform gain Numerical simulation results and experimental verification on the pulse evolution process in a photonics crystal fiber (PCF) femtosecond laser amplifier with different pump schemes are reported. A model combining rate equations with nonlinear Schrodinger equation, which considers the interaction among non-uniform gain distribution, group velocity dispersion and self-phase modulation within the fiber, is adopted. Compared with the amplification by forward pump scheme, the simulation results show that the amplified femtosecond pulse by backward pump scheme has not only a higher output power but also a narrower pulse duration and spectral width, i.e. a smaller time-bandwidth-product and less nonlinear accumulation. For the verification test, a photonic crystal fiber femtosecond laser amplifier with the two pump schemes is built. The experiment results are consistent with the numerical simulation, and the physical mechanism of amplified pulse evolution dynamics is discussed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 505005 (2015)
Continuous Distributed Fiber Strain Location Sensing Based on Optical Frequency Domain Reflectometry
Liu Kun, Feng Bowen, Liu Tiegen, Jiang Junfeng, and Du Yang
In the process of the safety text of the large infrastructure, strain is an important parameter which needs to be mainly detected. In order to measure the distribution of strain accurately, a method which is a continuous distributed fiber strain measurement sensing based on optical frequency domain reflectometry (OFDR)In the process of the safety text of the large infrastructure, strain is an important parameter which needs to be mainly detected. In order to measure the distribution of strain accurately, a method which is a continuous distributed fiber strain measurement sensing based on optical frequency domain reflectometry (OFDR) is presented. The method is on the basis of the principle of wavelength shifts of Rayleigh scattering and a demodulation algorithm of wavelength shift based on the movement window cross-correlation in spatial domain is used to gain the information of continuous distributed strain. The experimental results show that it can realize stable and effective stain sensing including the size and position in a range of 100 m whose sensing resolution can reach 20 cm. Compared with other sensing methods, it not only can text the strain quantificationally, gain the spatial information of the strain distribution, but also achieve a function of strain location..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 505006 (2015)
Rapid Communications
[in Chinese]
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Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 519001 (2015)
Optical Design and Fabrication
Design of a Large Aperture Beam Alignment Apparatus
Lu Lihua, Zhang Hongzhi, and Yu Fuli
In inertial confinement fusion (ICF) facilities, a high precision laser alignment apparatus is usually used to focus the laser beams on target with high accuracy. To satisfy the beam adjustment requirements of the SG-III laser facility, one laser alignment apparatus with motorized mirrors is designed and studied theoreIn inertial confinement fusion (ICF) facilities, a high precision laser alignment apparatus is usually used to focus the laser beams on target with high accuracy. To satisfy the beam adjustment requirements of the SG-III laser facility, one laser alignment apparatus with motorized mirrors is designed and studied theoretically as well as experimentally. It is shown that the pointing accuracy of the laser beam can be achieved by using two deferent types of the motorized mirrors. The linear drive mechanism proposed by connecting the rotation mechanism through flexible hinges can meet the beam directing requirement with an accuracy of 1 mrad within ±15 mrad range and has been verified on the SG-III laser facility..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 516001 (2015)
Design and Experimental Analysis of the System of Coupling Laser Plasma Emission Light into Optical Fiber
Wang Yin, Zhao Nanjing, Liu Wenqing, Yu Yang, Fang Li, Meng Deshuo, Hu Li, Gu Yanhong, Wang Yuanyuan, Ma Mingjun, Xiao Xue, Wang Yu, and Liu Jianguo
Designed system of coupling laser plasma emission light into optical fiber can improve efficiency of coupling plasma emission light into optical fiber and decrease system size simultaneously, which can provide hardware basis for the application of laser induced breakdown spectroscopy (LIBS) to fast, field, in-situ mateDesigned system of coupling laser plasma emission light into optical fiber can improve efficiency of coupling plasma emission light into optical fiber and decrease system size simultaneously, which can provide hardware basis for the application of laser induced breakdown spectroscopy (LIBS) to fast, field, in-situ material composition analysis. The coupling system consists of three lenses. The first single lens is used to collimate the light emitted from plasma and the reversed telephoto consisting of the other two lenses is used to couple the collimated light into optical fiber. Coupling efficiencies of the system are all above 92% at the analysis wavelengths of Pb, Cu, Ni, Cr and Cd. The diameter of the system aperture is less than 6mm and the total length of the system is less than 30 mm. The coupling system is used to detect Cr in soil and Pb in sludge from a lead battery factory, which is compared with the methods of using double lenses collecting system and using fiber only. It is proved that the characteristic spectral lines obtained by coupling system could be more obvious and easier to recognize, limits of the detection of elements would be lower and the spectral datum could be more stable, which could be in favor of subsequent spectral lines analysis and the concentration computations of elements..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 516002 (2015)
Fiber Spectrometer Optical Simulation Optimization and Calibration
Xu Danyang, Tong Jianping, Gao Jianxun, and Wang Fei
The optical system is the core part of a spectrometer, and it determines the basic properties and the volume of the entire instrument. Advantages and disadvantages of several optical systems are analyzed, and the asymmetric Czerny-Turner system is adopted. The resulting optical path optimized with Zemax has an overall The optical system is the core part of a spectrometer, and it determines the basic properties and the volume of the entire instrument. Advantages and disadvantages of several optical systems are analyzed, and the asymmetric Czerny-Turner system is adopted. The resulting optical path optimized with Zemax has an overall resolution of 1.8 nm, and a measurement range of 200~900 nm. Relative error of wavelength is controlled to be below 0.05 nm, with cubic spline interporlation coefficients obtained from Matlab and HG- 1 mercury- argon used as the calibration light source. Analyses on data for comparision with the USB4000 fiber spectrometer show that both of the design and implementation are feasible..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 516003 (2015)
Remote Sensing and Sensors
Study on Double Defect Mode Sensing Mechanism of Air Gate Photonic Crystal Based on Tight-binding Method
Chen Ying, Shi Jia, Lu Bo, Liu Teng, Dong Jing, Zhu Qiguang, and Chen Weidong
In order to reduce the interference of ambient temperature changes to the single defect photonic crystal sensing, a double defect mode sensing model of air gate photonic crystal is proposed. The mechanism of the double defect mode is analyzed by tight- binding method, and the optical transmission property of the photonIn order to reduce the interference of ambient temperature changes to the single defect photonic crystal sensing, a double defect mode sensing model of air gate photonic crystal is proposed. The mechanism of the double defect mode is analyzed by tight- binding method, and the optical transmission property of the photonic crystal structure is analyzed by the transmission matrix method. For the cross- sensitive issue of temperature and refractive index, a method to eliminate the temperature interference is proposed, and the relation model between the two defect mode wavelengths and the structure parameters of the photonic crystal are established. Using the air gate photonic crystal structure, the dynamic monitoring of the detected gas sample parameters can be achieved from the shift of the resonant transmission peak. The numerical simulation shows that the relation between double defect sensor has the features of double defect mode wavelengths and the gas refractive index is linear. The sensor has the advantages of simple structure and high precision..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 514001 (2015)
Spectroscopy
Application of GA-BP Neural Network in Detection of Trace Phosphate
Wang Shutao, Wang Xinglong, Chen Dongying, Wei Meng, and Wang Zhifang
Based on the principle of molecule fluorescence of rhodamine 6G, the fluorescence spectra under different experimental conditions are compared and the maximum fluorescence intensity is obtained when pH is 1. When molybdate, potassium dihydrogen phosphate and sulfuric acid are added into the rhodamine 6G reagent the comBased on the principle of molecule fluorescence of rhodamine 6G, the fluorescence spectra under different experimental conditions are compared and the maximum fluorescence intensity is obtained when pH is 1. When molybdate, potassium dihydrogen phosphate and sulfuric acid are added into the rhodamine 6G reagent the complex is generated and the fluorescence intensity of rhodamine 6G declines. Within a certain range, it exhibits linear relationship. The position of fluorescence peak does not change. A nonlinear model is constructed based on genetic algorithm-back propagation (GA-BP) neural network which consists of a 36×18 matrix as inputs and a 1 × 18 matrix as outputs, and its purpose is to detect the phosphate concentration. In network training, the error accuracy is 10-3 and the correlation coefficient between the outputs and the expectations is 0.998. In network prediction, the average recovery is 99%, while the average standard deviation is 1.79% , reaching the ideal results. Therefore, this network can better detect phosphate concentration of 0~2.00 mg/L. In summary, a quick and effective way to detect phosphate concentration is provided, which helps promote the development and application of environmental monitoring technique..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 515001 (2015)
Study of Spectral Characteristics of External Cavity Diode Laser Using Transversely Chirped Volume Bragg Grating
Wang Junzhen, Wang Yuefeng, Yu Xinfeng, Ren Yongxue, Bai Huijun, and Lei Chengqiang
The diffraction characteristics of transversely chirped volume Bragg grating are analyzed using beam propagation method. The power, spectral and wavelength tuning characteristics of external cavity diode laser analyzed by laser using transversely chirped volume Bragg grating are demonstrated. The theoretical and experiThe diffraction characteristics of transversely chirped volume Bragg grating are analyzed using beam propagation method. The power, spectral and wavelength tuning characteristics of external cavity diode laser analyzed by laser using transversely chirped volume Bragg grating are demonstrated. The theoretical and experimental results indicate that the peak diffraction efficiency of transversely chirped volume Bragg grating decreases with increasing the size of the incident beam in chirped direction, the spectral width increases with increasing the size of the incident beam in chirped direction. When the chirped direction of the transversely chirped volume Bragg grating is consistent with the fast axis direction of diode laser, external cavity efficiency of external cavity diode laser is 85% , the spectral width of the output laser at 808.05 nm is 0.27 nm. When the chirped direction of the transversely chirped volume Bragg grating is consistent with the slow axis direction of diode laser, external cavity efficiency of external cavity diode laser is 89% , the spectral width of the output laser at 808.05 nm is 0.3 nm. Both of the external cavity diode lasers have a better way to achieve about 15 nm wavelength tunable range, and within the entire tuning range, the fluctuation range of output power are less than 1% (consistent with the fast axis direction) and 1.5% (consistent with the slow axis direction) respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 515002 (2015)
Algae Chemotaxonomy Technology by Fluorescence Based on Alternating Trilinear Decomposition Analysis
Wu Zhenzhen, Yao Peng, Su Rongguo, Chen Xiaona, and Shi Xiaoyong
A fluorescence-excitation-emission-matrix (EEM) method for the determination of algae community composition is developed by alternating trilinear decomposition (ATLD) analysis and nonnegative least squares (NNLS). ATLD model is applied to fluorescence EEMs of algal pigment extracts, and 14 fluorescent components are idA fluorescence-excitation-emission-matrix (EEM) method for the determination of algae community composition is developed by alternating trilinear decomposition (ATLD) analysis and nonnegative least squares (NNLS). ATLD model is applied to fluorescence EEMs of algal pigment extracts, and 14 fluorescent components are identified according to the residual sum of squares. Bayesian discriminant analysis is used to test the discriminatory capability of 14 fluorescent components. All composition spectra of the fluorescent components for the 48 phytoplankton species are spectrographically clustered into 116 reference spectra by hierarchical cluster analysis. The fluorometric method is developed by NNLS and applied to algal samples. For 512 samples of singlespecies, the average correctly discriminated rate (CDR) of the five phytoplankton groups is 99.8%. The CDR for the 256 mixture samples is above 93.5% for the dominant algae species and above 71.1% for the subdominant algae species. This method is also tested by the 18 samples from the Yangtze River estuary, the results of the dominant algae groups are in good agreement with HPLC (high performance liquid chromatography)-CHEMTAX..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 515003 (2015)
Application of Fluorescence Spectroscopy and PSO-BP Neural Network in the Detection of Potassium Sorbate Concentration
Wang Shutao, Chen Dongying, Wei Meng, Wang Xinglong, Wang Zhifang, and Wang Jialiang
Potassium sorbate, one of preservatives, has been used widely, but it will do harm to human health if it is overtaken. Fluorescence spectrum properties of potassium sorbate in aqueous solution and orange juice are studied. The results show that the fluorescence characteristic peak of potassium sorbate in aqueous solutiPotassium sorbate, one of preservatives, has been used widely, but it will do harm to human health if it is overtaken. Fluorescence spectrum properties of potassium sorbate in aqueous solution and orange juice are studied. The results show that the fluorescence characteristic peak of potassium sorbate in aqueous solution exists at λex /λem = 375 nm/485 nm , the mixture of potassium sorbate and orange juice has a side peak at λex /λem = 470 nm/540 nm besides the fluorescence characteristic peak. In the mixture, there is mutual interference of fluorescence characteristic between potassium sorbate and orange juice, which makes the concentration detection of potassium sorbate more difficult. To determine the concentration of potassium sorbate in the mixture, back propagation neural network optimized by particle swarm optimization (PSO- BP) is applied. The average recovery rate of the 3 prediction samples is 98.97%, and the range in which the PSO-BP neural network can accurately measure the concentration of potassium sorbate in the mixture is 0.1~2.0 g/L. The prediction results indicate that the method combining fluorescence spectrum and PSO-BP neural network can effectively detect the concentration of potassium sorbate in orange juice..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 5, 515004 (2015)
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