Journals >Chinese Journal of Lasers
Contents
2011
Volume: 38 Issue 8
44 Article(s)
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Biomedical Photonics and Laser Medicine
Modulation of Low Intensity Laser Irradiation on Expression Suppression of Circadian Clock Genes in Cultured Fibroblasts
Zhu Ling, Wu Defeng, Wang Yongqing, and Liu Chengyi
The effects of low intensity 810 nm laser irradiation (LIDL) to the tumor necrosis factor (TNF)-α induced expression suppression of circadian clock genes in cultured NIH3T3 fibroblasts are investigated. The fibroblasts shocked by horse serum for 2 h are induced with TNF-α of 10 ng/mL, and then irradiated by different dThe effects of low intensity 810 nm laser irradiation (LIDL) to the tumor necrosis factor (TNF)-α induced expression suppression of circadian clock genes in cultured NIH3T3 fibroblasts are investigated. The fibroblasts shocked by horse serum for 2 h are induced with TNF-α of 10 ng/mL, and then irradiated by different doses of LIDL once. The results show that TNF-α induced inhibition effect of the circadian clock gene expression can be modulated by LIDL, which may be mediated by nicotinamide adenine dinucleotide/ reduced form of nicotinamide adenine dinucleotid (NAD+/NADH) and sirtuin 1 (SIRT1)..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 804001 (2011)
Laser Devices and Laser Physics
Concept and Prospect of Quantum System Based Fiber Laser Beam Combination with Super High Brightness
Xu Xiaojun, Yang Zining, Wang Hongyan, and Lu Qisheng
The advantages and disadvantages of single aperture fiber lasers are discussed; the high power scaling ability of some sophisticated fiber laser combining technologies is analyzed. A new concept of fiber laser combining technology based quantum system is proposed; the future development of such system is forecasted, anThe advantages and disadvantages of single aperture fiber lasers are discussed; the high power scaling ability of some sophisticated fiber laser combining technologies is analyzed. A new concept of fiber laser combining technology based quantum system is proposed; the future development of such system is forecasted, and this new combination concept is thought to be greatly potential in scaling to extremely high brightness laser operation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 801001 (2011)
Laser Manufacturing
Investigation on Laser Surface Modification of Copper
Li Mingyu, Chao Mingju, Liang Erjun, Zhang Junji, and Li Dechuan
A good finish layer which is free from surface crack is successfully fabricated by laser surface modification on copper. The microstructure, phase structure and tribological properties are investigated by means of scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS) and X-ray diffractometer (XRD), aA good finish layer which is free from surface crack is successfully fabricated by laser surface modification on copper. The microstructure, phase structure and tribological properties are investigated by means of scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS) and X-ray diffractometer (XRD), as well as dry sliding wear test. The hardness and electrical conductivity tests are also carried out. The results indicate that the modified layer is composed of a fine and homogeneous microstructure, which has the characteristic of rapid solidification. The modified layer has a high average hardness of 625 HV0.1 and better wear resistance. The wear mass loss of the layer is only one fifth of that of pure copper. Additionally, the electrical conductivity is slightly lowered by laser surface modification. The improvement of hardness and wear resistance is attributed to refinement and solid solution strengthening in the modified layer. The level of the electrical conductivity depends on the dilution..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 803001 (2011)
Study on Strain Hardening and Fatigue Fracture of AZ31B Magnesium Alloy after Laser Shot Peening
Huang Shu, Zhou Jianzhong, Jiang Suqin, Sheng Jie, Xu Zengchuang, and Ruan Hongyan
Laser shot peening (LSP) and tensile fatigue test are carried out on AZ31B magnesium alloy samples with center hole. The surface integrity is compared before and after LSP, which indicates that plastic deformation is induced by slip and twinning after LSP, the micro-hardness along surface and depth direction increases Laser shot peening (LSP) and tensile fatigue test are carried out on AZ31B magnesium alloy samples with center hole. The surface integrity is compared before and after LSP, which indicates that plastic deformation is induced by slip and twinning after LSP, the micro-hardness along surface and depth direction increases by about 50%, while the surface residual compressive stress value reaches to -126.29 MPa, and grain is refined since a large number of slip lines and twins appear. Fatigue performance is analyzed by testing axial force and axial displacement, meanwhile fatigue fracture is compared before and after LSP. No obvious source of fatigue crack is found on the surface after LSP, the actual stress intensity factor of crack tip is reduced by residual compressive stress, thereby fatigue crack initiation and propagation resistance is improved. Fatigue crack growth path is more tortuous than untreated pieces. Dimple size of final breaking zone is larger and deeper than untreated pieces, which indicates that the plastic has been improved after LSP..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 803002 (2011)
Computations of Laser Shock Processing by Smoothed Particle Hydrodynamics
Zhou Liucheng, Li Yinghong, He Weifeng, Zhou Lei, and Chen Donglin
Propagation of detonation waves and space-time regularities of distribution in laser shock processing is investigated, a new numerical simulation model of laser shock processing (LSP) is established by smoothed particle hydrodynamics (SPH) in contrast to finite element simulation method, and verified by experiments. RePropagation of detonation waves and space-time regularities of distribution in laser shock processing is investigated, a new numerical simulation model of laser shock processing (LSP) is established by smoothed particle hydrodynamics (SPH) in contrast to finite element simulation method, and verified by experiments. Results show that SPH model has obvious physical process and good similarity to experimental results, providing a new mean for laser shock processing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 803003 (2011)
Component′s Surface Quality Predictions by Laser Rapid Forming Based on Artificial Neural Networks
Yang Donghui, Ma Liang, and Huang Weidong
A single-channel polyline scanning mathematical model is established, and the mathematical description of surface quality is analyzed theoretically. It is drew the conclusion that the angle degree and the scanning speed are the main important process parameters for part surface quality. The artificial neutral networks A single-channel polyline scanning mathematical model is established, and the mathematical description of surface quality is analyzed theoretically. It is drew the conclusion that the angle degree and the scanning speed are the main important process parameters for part surface quality. The artificial neutral networks (ANN) model is established to predict part surface quality based on laser solid forming (LSF). The input of this model is the angle degree of corner joint and the scanning speed which is the most important factor in LSF process. The output of this model is the data of surface characterization which is the difference between corner joint height and layers′ height. The ANN model could predict parts′ surface quality data under different corner joint′ angle degree conditions after trainied by experimental data. The mean squared error (MSE) is less than 0.01 between prediction data and experimental data..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 803004 (2011)
Numerical Simulation of Laser Induced Ultrasonic in a Diamond Anvil Cell by Finite Element Method
Feng Wen, Yang Dexing, Liao Wei, and Guo Yuning
A numerical simulation model for a pulsed laser induced ultrasonic in a diamond anvil cell (DAC) is established by using finite element method (FEM). The transient temperature field and ultrasonic displacement field in sample under high pressure are simulated. Ultrasonic waveforms at different positions in the rear facA numerical simulation model for a pulsed laser induced ultrasonic in a diamond anvil cell (DAC) is established by using finite element method (FEM). The transient temperature field and ultrasonic displacement field in sample under high pressure are simulated. Ultrasonic waveforms at different positions in the rear face of sample under the irradiation of a vertically incident laser pulse are obtained, and the characteristics of ultrasonic displacement field changing with time are analyzed. The numerical results show that, ultrasonic wave generated in thermoelastic effect has obvious directionality in a DAC. The energy of longitudinal wave is concentrated near the laser incident direction, and the energy of shear wave is concentrated between 30° and 55° that deflects from the laser incident point. The characteristics are different from the results of free surface in thermoelastic effect, but they are similar to the results of free surface in ablation effect..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 803005 (2011)
Laser Parameters Influence in Direct-Part Marking Barcodes on Aluminum Alloy
Qiu Huadong, Lu Changhou, and Xiao Rujing
Different laser parameters and the interactional production can affect the barcode grade profoundly. In order to effectively mark barcodes on aluminum alloy with a laser, it is important to search out the optimum parameters and establish a relationship between critical laser parameters and the quality of the symbol. A Different laser parameters and the interactional production can affect the barcode grade profoundly. In order to effectively mark barcodes on aluminum alloy with a laser, it is important to search out the optimum parameters and establish a relationship between critical laser parameters and the quality of the symbol. A NdYAG laser is utilized to produce 3136 Data Matrix symbols onto aluminum substrates. The experiment focuses on all interval values of the vector step, inter-step time, laser Q frequency and laser Q release time. From the experimental results, the optimized parameters are the vector step of 0.005~0.009 mm, the inter-step time of 29~43 μs, laser Q frequency of 7~10 kHz, and laser Q release time of 13~19 μs. And then, by analyzing the higher and the lower power density processing module scanning electron microscope (SEM) images and energy dispersive spectrometer (EDS) data, it is found that the interaction between the laser and the aluminum alloy can be divided into four stages. This can explain the laser parameters and materials influence on barcode grade in microstructure and micro-components..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 803006 (2011)
Microstructure and Properties of Laser Cladded Coating of Mechanical Alloying Powders of 19Cr-14Ni Stainless Steel Power
Lou Deyuan, He Chunlin, Chen Changyi, Chen Jiang, Liu Changsheng, and Cai Qingkui
Generally, the powders that used in laser cladding are atomized. To explore new technology the powders used for laser cladding, atomized powders of 19Cr-14Ni type of stainless steel (mixed by element powders) are mechanically alloyed for 45 h. Then, the two kinds of powders are cladded on 45# steel. Finally, X-ray diffGenerally, the powders that used in laser cladding are atomized. To explore new technology the powders used for laser cladding, atomized powders of 19Cr-14Ni type of stainless steel (mixed by element powders) are mechanically alloyed for 45 h. Then, the two kinds of powders are cladded on 45# steel. Finally, X-ray diffraction (XRD), scanning electron micrscope (SEM)/energy dispersive spectroscopy (EDS) and electrochemical methods are utilized to investigate the phases composition, microstructure and corrosion behavior of the two laser cladded coatings method. The results show that the grains of laser cladded coating with mechanical alloying (MA) powders are much finer than that of the coating with atomized powders. Due to the formation of net-like structure and the decrease in Cr element segregation between dendritic crystals, the corrosion resistance of MA laser coating is improved. However, its microhardness is slightly decreased..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 803007 (2011)
Research on Processing of Laser Cladding Ta-W Alloy Coatings
Wu Yang, Yu Gang, He Xiuli, Ning Weijian, Zheng Caiyun, and Zhang Yongjie
Ta-W alloy coatings were deposited on pure Ta plate by laser cladding with pre-coating and coaxial powder injection respectively in order to find the effects with two technique. The microstructure of the coatings was analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The microhaTa-W alloy coatings were deposited on pure Ta plate by laser cladding with pre-coating and coaxial powder injection respectively in order to find the effects with two technique. The microstructure of the coatings was analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The microhardness was examined by hardness tester. The clad layer which formed with pre-coating had a microstructure of coarse columnar grain and low dilution rate with the substrate. The average microhardness of the clad layer was 1500 HV, it was 10 times greater than the Ta substrate. The clad layer deposited with coaxial power injection had a microstructure consisting of dendrite Ta-W solid solution uniformly dispersed in the Ta matrix. The average microhardness of the clad layer was approximately 800 HV and it was 5 times greater than that of the substrate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 803008 (2011)
High-Temperature Oxidation Properties of Fe-Based Alloy Coating Prepared by Laser Cladding
Han Bin, Li Meiyan, and Wang Yong
Fe-based alloy composite coating is produced by laser cladding Fe-base powder containing Cr3C2 powder. The morphology and component of the oxide scales of laser cladding coating at 600 ℃ for 100 h are analyzed by means of scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRFe-based alloy composite coating is produced by laser cladding Fe-base powder containing Cr3C2 powder. The morphology and component of the oxide scales of laser cladding coating at 600 ℃ for 100 h are analyzed by means of scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The results show that the microstructures of the Fe-based alloy composite coatings are uniform and dense without cracks and pores. At 600 ℃ the high-temperature oxidation resistance of the Fe-based composite coatings with Cr3C2 powder is improved obviously compared with the matrix and the accumulative oxidation mass-gain and oxidation ratio are less than the matrix. At 600 ℃ FeCr2O4 spinel oxide are formed on the surface of the pure Fe-base alloy coating with better high-temperature oxidation resistance. With the addition of Cr3C2 powder, Cr3C2 is decomposed at high temperature and the content of Cr in the molten pool is improved significantly, resulting in the formation of the continuous and complete Cr2O3 scales, and the improvement of the high-temperature oxidation resistance compared with the coating without Cr3C2 powder..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 803009 (2011)
Development of LD Pumped Nd:YAG Laser Texturing Device with High Performance
Cao Zexin, Zhang Chunjie, Liu Ling, Zhao Xiaobai, Ge Zhe, and Liu Chang
Development of roll texturing with LD pumped acousto-optically Q-switched Nd:YAG laser and the texturing experiments are carried out. With the request of roughening reticular density of 4 mm×4 mm, the chromium rolls are textured using this laser texturing device. The result realizes excellent performance that the Development of roll texturing with LD pumped acousto-optically Q-switched Nd:YAG laser and the texturing experiments are carried out. With the request of roughening reticular density of 4 mm×4 mm, the chromium rolls are textured using this laser texturing device. The result realizes excellent performance that the roughness is adjustable within the scope of 6 μm under the frequency of 2.8 kHz and the adjustable range is 4.5 μm under the frequency of 5.6 kHz. It realizes successfully the development of LD pumped Nd:YAG laser texturing device with long adjustable roughness range, high efficiency, long life time and low operating cost..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 803010 (2011)
Effect of h-BN Content on Microstructures and Wear Resistance of Laser Cladding Self-lubricant Coatings
Niu Wei, and Sun Ronglu
Ni+h-BN self-lubricating composite coatings are prepared on H13 steel substrate by CO2 laser cladding with powder mixtures of Ni60 and h-BN. The chemical compositions and microstructures of the coatings are analyzed by using optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDNi+h-BN self-lubricating composite coatings are prepared on H13 steel substrate by CO2 laser cladding with powder mixtures of Ni60 and h-BN. The chemical compositions and microstructures of the coatings are analyzed by using optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The microhardness profile of the coatings along the depth direction is measured on a microhardness tester. The friction properties are investigated by using on a pin-on-ring M200 wear tester. The results show that, the microstructure of Ni60+5%h-BN (mass fraction) coating are consisted of wattle-like phase Cr2N and a few irregular block-like phase CrB distributed in γ-Ni matrix, Ni60+10%h-BN coating is consisted of short-plate phase CrB and Ni60+15%h-BN coating is consisted of dendritic-plate phase CrB. With the content of h-BN increasing, the microhardness of the Ni60+h-BN coatings increases and the friction coefficient reduces. The maximal microhardness 1200 HV0.2 is 4 times more than that of the substrate. The friction coefficient and wear mass loss of the Ni+h-BN coatings are lower than those of the Ni60 coating, respectively. The minimum wear mass loss of the Ni+h-BN coating is 6% of that of the substrate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 803011 (2011)
Control of Process Parameters of Reducing Solid of Revolution with Coaxial Inside-Beam Powder Feeding Accumulation
Li Hongyuan, Shi Shihong, Fu Geyan, Wang Yongkang, Cai Qifei, Wang Chen, and Sun Houshun
Based on the patent technology of “hollow laser beam and internal powder feeding”, the accumulation experiments of the reducing solid of revolution are carried out on the substrate of 45# steel with a novel device of coaxial inside-beam powder feeding. In the experiment, we respectively control the axially symmetrical Based on the patent technology of “hollow laser beam and internal powder feeding”, the accumulation experiments of the reducing solid of revolution are carried out on the substrate of 45# steel with a novel device of coaxial inside-beam powder feeding. In the experiment, we respectively control the axially symmetrical rake, Z axis incremental and power, and analyze their respective influence. The conclusions are as follows: In the inclined wall depositing process, the skew angle is in direct ratio to offset and scanning rate and is inversely proportional to powder delivery rate and powder utilization ratio. The limit skew angle is in direct ratio to the offset and is inversely proportional to the height of the cladding layer. With the cladding layers increasing, the utilization rate of the powder is reduced and the defocus distance becomes bigger. In the process of high-rise cladding accumulation, molten pool changes from 3D cooling into 2D heat dissipation and formed pool temperature arises, and so the power rate should be reduced correspondingly. The quality of molding parts that this experiment gets finally is higher with smooth appearance and lower roughness. It can provide reference to the test of the variable cross-section 3D accumulation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 803012 (2011)
Laser Physics
Passively Mode-Locked and Q-Switched Yb-Doped Fiber Lasers with Graphene-Based Saturable Absorber
Liu Jiang, Wu Sida, Wang Ke, Cao Yi, Yang Quanhong, and Wang Pu
A graphene-based passively mode-locked and passively Q-switched Yb-doped fiber laser is reported. Stable mode-locked pulse train occurres at about 1.2 W incident pump power and the pulse repetition rate is 1.04 MHz in a ring cavity configuration; increasing the incident pump power to 2.3 W, the pulse width is measured A graphene-based passively mode-locked and passively Q-switched Yb-doped fiber laser is reported. Stable mode-locked pulse train occurres at about 1.2 W incident pump power and the pulse repetition rate is 1.04 MHz in a ring cavity configuration; increasing the incident pump power to 2.3 W, the pulse width is measured to be about 680 ps and the output power is 170 mW, which corresponds to single pulse energy of 163 nJ. Graphene-based passively Q-switched operation is also demonstrated with pulse width of 70 ns and maximum output power of 12 mW in a linear cavity configuration, which corresponds to single pulse energy of 46 nJ. The repetition rate is tunable from 140 to 257 kHz along with the increase of the pump power..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 802001 (2011)
Pure Single Mode Output of Six-Core Fiber Laser Based on Single-Mode Fiber Mode Selection
Zhang Xiaolei, Peng Gangding, Zhang Xingyu, Wang Qingpu, and Chang Jun
A multi-core fiber laser with single-mode output is reported, which is mode selected by the proposed mechanism based on single-mode fiber. Using single-mode fiber combined with a total reflection mirror as mode selection element, the in-phase supermode always has much higher coupling coefficient than that of the other A multi-core fiber laser with single-mode output is reported, which is mode selected by the proposed mechanism based on single-mode fiber. Using single-mode fiber combined with a total reflection mirror as mode selection element, the in-phase supermode always has much higher coupling coefficient than that of the other higher-order supermodes. As a result, high brightness single in-phase supermode output is obtained while higher-order supermodes are suppressed. The coupling coefficient can be optimized by choosing proper single-mode fiber core radius and adjusting the gap distance between multi-core fiber and single-mode fiber. The relationship between coupling coefficient and single-mode output power is investigated. The simulation results got from rate equation show that the output power increases with coupling coefficient, and the maximum optical-optical conversion efficiency is calculated to be 63.7%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 802002 (2011)
Passively Mode-Locked Yb-Doped Fiber Laser with Graphene Epitaxially Grown on 6H-SiC Substrates
Liu Jiang, Wei Rusheng, Xu Jia, Xu Xiangang, and Wang Pu
We report all-normal-dispersion passively mode-locked Yb-doped fiber laser by graphene epitaxially grown on 6H-SiC substrates in a ring cavity configuration. Stable mode-locked pulses of the fiber laser are obtained at about 250 mW incident pump power and the pulse repetition rate is 1.05 MHz; Increasing the incident pWe report all-normal-dispersion passively mode-locked Yb-doped fiber laser by graphene epitaxially grown on 6H-SiC substrates in a ring cavity configuration. Stable mode-locked pulses of the fiber laser are obtained at about 250 mW incident pump power and the pulse repetition rate is 1.05 MHz; Increasing the incident pump power to 480 mW, the average output power is 20 mW, which corresponds to single pulse energy of up to 19 nJ with pulse width of about 520 ps..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 802003 (2011)
Polarization Properties of Partially Coherent Electromagnetic Beams in Three Points′ Interference Pattern
Chen Kai, Cao Jianqiu, and Lu Qisheng
The cross-spectral density matrix in three points′ interference pattern is derived, and the variation of polarization properties of partially coherent beams under this condition is given. A comparation between the cases of unrelated and related field components of x-direction and y-direction is studied, and compared wiThe cross-spectral density matrix in three points′ interference pattern is derived, and the variation of polarization properties of partially coherent beams under this condition is given. A comparation between the cases of unrelated and related field components of x-direction and y-direction is studied, and compared with two points′ interference pattern in the same conditions. It is shown that the degree of polarization is oscillating in the observation plane. The farther away from the center, the more intense the oscillation is. The degree of polarization at different positions tends to the stable value after a long-propagation distance, which is related to the parameters of Bxy and δxy. The farther away from the center, the longer-propagation distance that the degree of polarization tends to be stable. The degree of polarization on the axes is closely related to the initial degree of coherence of three points. In particular, when field components of x-direction and y-direction are related, the degree of polarization at the corresponding point is much larger than the case of unrelated field components..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 802004 (2011)
Study of High-Power Broad Area Distributed-Feedback Laser
Zhao Yihao, Wang Jun, Wang Cuiluan, Liu Suping, and Ma Xiaoyu
High-power semiconductor laser is commonly used for pump source, but the absorption spectra width of the ion which is pumped by the laser is often small. In order to improve the pumping efficiency of high-power semiconductor laser to solid or fiber laser, the current and thermal drift coefficient of wavelength should bHigh-power semiconductor laser is commonly used for pump source, but the absorption spectra width of the ion which is pumped by the laser is often small. In order to improve the pumping efficiency of high-power semiconductor laser to solid or fiber laser, the current and thermal drift coefficient of wavelength should be decreased. The influence of grating depth and grating duty cycle with the laser wavelength stabilized effect are analyzed theoretically. The appropriate grating parameter is obtained by experimental verification. And the appropriate laser cavity length is obtained according to the optimized condition. The first broad area distributed-feedback (DFB) laser whose wavelength is well-locked is fabricated interiorly. The broad area DFB laser single emitter with 2.4 mm cavity length, 100 μm stripe width produce coutinuous-wave output power of 400 mW at 15 ℃ heatsink temperature and its wavelength is 954 nm. The current drift of wavelength on this DFB laser is 0.67 nm/A and the thermal drift coefficient of wavelength on this DFB laser is 0.046 nm/K..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 802005 (2011)
Application of Hartmann-Shack Wave Front Detector in Testing Distorted Wave Front of Conduction Cooled End-Pumped Slab
Xu Liujing, Yang Ping, Liang Xingbo, Wang Chao, Tang Xiaojun, Liu Yang, Liu Lei, and Zhao Hong
High power and good beam quality of solid laser has potential applications in modern industrial processing and scientific research, while the parameters of laser are affected by the dynamic thermal distortion caused by the thermal effect in solid state laser. Taking wave front distortion of the laser and advantage of tHigh power and good beam quality of solid laser has potential applications in modern industrial processing and scientific research, while the parameters of laser are affected by the dynamic thermal distortion caused by the thermal effect in solid state laser. Taking wave front distortion of the laser and advantage of the conduction cooled end-pumped slab (CCEPS) as a starting point, the wave front distortion caused by thermal effect in the CCEPS is measured by use of Hartmann-Shack wave front detector. By the analysis of results in the measurements of the aberration in the CCEPS, when the output power is different, the dynamic thermal distortion is obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 802006 (2011)
Measurement of Phase-Matching Angle of KTP Crystal Applied for Third Harmonic Generation of 1319 nm Laser at Room Temperature
Wen Wuqi, Kang Jianyi, Zhai Ning, Ding Xin, Lu Ying, Zhou Rui, Sheng Quan, and Yao Jianquan
For the aim of third harmonic generation (THG) experiment of NdYAG 1319 nm laser to produce 440 nm blue laser using KTP crystal at room temperature, theoretical calculation and experimental study have been carried out for the THG phase-matching angle of KTP crystal. Using several sellmeier equations, phase-matching angFor the aim of third harmonic generation (THG) experiment of NdYAG 1319 nm laser to produce 440 nm blue laser using KTP crystal at room temperature, theoretical calculation and experimental study have been carried out for the THG phase-matching angle of KTP crystal. Using several sellmeier equations, phase-matching angles are derived, and corresponding effective nonlinear coefficients are calculated. One result (θ=84.6°, φ=0°) of the angles is chosen to cut KTP crystal, and then by using a laser of 1319 nm, crystals are carried into the cavity, methods of rotating the crystal and adjusting the temperature to find out optimum phase matching angle of the KTP crystal for THG (θ=85.04°, φ=0°) are applied. After re-cutting KTP crystal, the beam intensity of outputting 440 nm blue laser has a significant improvement and the optimum operating temperature is 18 ℃..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 802007 (2011)
397 nm Semiconductor Laser Stabilized with Scanning Transfer Cavity
Qu Wancheng, Huang Yao, Guan Hua, Huang Xueren, and Gao Kelin
Because of the large long-term drift, the commercial semiconductor laser cannot meet the requirement of the experiments of laser cooling and probing of single ions trapped in ion traps of optical frequency standards for a long time. So, the transfer cavity is used to reduce the long-term drift of a commercial 397 nm laBecause of the large long-term drift, the commercial semiconductor laser cannot meet the requirement of the experiments of laser cooling and probing of single ions trapped in ion traps of optical frequency standards for a long time. So, the transfer cavity is used to reduce the long-term drift of a commercial 397 nm laser. An ultra-narrow 729 nm laser stabilized to a super cavity by Pound-Drever-Hall (PDH) scheme is used as reference, and a scanning Fabry-Perot (F-P) cavity is used as transfer medium. The 397 nm laser′s long-term drift is reduced to less than 1 MHz within 1 h, and the square root of the Allan variance is 1×10-10 at an averaging time of 102 s. These parameters are the base for stabilizing an 866 nm laser and optimizing the laser cooling and long-term measurement of single 40Ca+ ion..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 802008 (2011)
Tip-Tilt Correction and Coherent Combination of Seven-Channel Laser Array Based on Active Segmented Mirrors
Zheng Yi, Wang Xiaohua, Shen Feng, and Li Xinyang
A novel method for laser array phasing is proposed. The active segmented mirror (ASM) is adopted to solve two key problems in the coherent beam combination of master oscillator power amplifiers (MOPA-CBC). The two key problems are the alignment of spatial beamlets and the phase modulation on system′s output end. The moA novel method for laser array phasing is proposed. The active segmented mirror (ASM) is adopted to solve two key problems in the coherent beam combination of master oscillator power amplifiers (MOPA-CBC). The two key problems are the alignment of spatial beamlets and the phase modulation on system′s output end. The modulation principle of a seven-element ASM is introduced. Based on this device, the experimental verification of a seven-channel laser array is successfully accomplished. The spatial beamlets combination is implemented by a hexagonal pyramid. Two individual control loops are adopted to implement the piston and tip-tilt corrections. The precisions achieve lower than 25 μrad and λ/10. In close loop, the combined output laser with high quality has been obtained. The power fraction in main lobe achieves is 31.73%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 802009 (2011)
1030 nm High Repetition Rate Nanosecond Pulse All Fiber Amplifier
Zhou Cuiyun, Liu Yuan, Du Songtao, Yang Yan, Wu Yaofang, Hou Xia, and Chen Weibiao
An all fiber pulse master oscillator power amplifier (MOPA) system with Yb3+-doped fiber is reported. The seeder is a single longitudinal mode directly modulated laser diode which operates in wavelength of 1030 nm and tunable repetition rate ranging from 50 kHz to 100 kHz. This all-fiber amplifier could generate up to An all fiber pulse master oscillator power amplifier (MOPA) system with Yb3+-doped fiber is reported. The seeder is a single longitudinal mode directly modulated laser diode which operates in wavelength of 1030 nm and tunable repetition rate ranging from 50 kHz to 100 kHz. This all-fiber amplifier could generate up to 16.08 kW peak power at the center wavelength of 1029.49 nm, with a pulse duration of 6.53 ns and a slope efficiency of 69% (at 50 kHz repetition rate). The output average power and pulse temporal characteristics with variation of repetition rate are also studied. The output laser wavelength is in the spectral responsivity range of lidar detectors and could be used as laser source for lidar..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 802010 (2011)
High Power and High Reliability Vertical-Cavity Surface-Emitting Laser Array
Cui Jinjiang, Ning Yongqiang, Jiang Chenyu, Wang Fan, Shi Yanbo, Dong Ningning, Tian Yubing, Tan Huiming, and Wu Xiaodong
We design InGaAs/GaAsP periodic gain structure quantum wells for 980 nm laser wavelength. The GaAsP material with a wider band gap is used as the barrier layer instead of conventional material GaAs. It will solve the problem that the efficiency is decreased with increasing temperature, and will meet the requirement of We design InGaAs/GaAsP periodic gain structure quantum wells for 980 nm laser wavelength. The GaAsP material with a wider band gap is used as the barrier layer instead of conventional material GaAs. It will solve the problem that the efficiency is decreased with increasing temperature, and will meet the requirement of long-life laser working. The periodic gain structure quantum wells will increase the gain, decrease the threshold current and improve the output power. The new structured 4×4 array with an element aperture of 30 μm has a 2 W continuous output power at 5.88 A current. The narrow pulse output power can reach to 30 W at the pulse width of 1 μs, repetition rate of 100 Hz, and work current of 60 A. The results all above have not reached saturation. The far-field angles at the current of 1～4 A are all below 16°. We test the reliability of the array. The life at 30 ℃ is as high as 5280 h or above. The main factors affecting the reliability of high power vertical-cavity surface-emitting laser (VCSEL) are studied..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 802011 (2011)
Materials and Thin Films
Mathematical Model of Aging and the Life Test Method for GaN LED
Yu Fei, and Jin Lei
GaN LED has got an extensive application for its life, efficiency, environmental protection and other advantages. The life question has been the core question, which limits the application of the GaN LED. In order to research the GaN LED aging process, calculate GaN LED physical parameters, such as life time and so on,GaN LED has got an extensive application for its life, efficiency, environmental protection and other advantages. The life question has been the core question, which limits the application of the GaN LED. In order to research the GaN LED aging process, calculate GaN LED physical parameters, such as life time and so on, the aging principle of deep level GaN LED defects and the non-radiation recombination centers increasing are analyzed. And according to the principle, we analyze the physical theory of GaN LED aging process, and finally establish an aging mathematical model for a GaN LED. Meanwhile, through a calculation of a set of practical GaN LED big stress aging experiment data with the aging mathematical model, a test method and mathematics calculation method of the life time are established, and finally we calculate the experimental GaN LED life value. Compared with the traditional Allen News model, the GaN LED aging mathematical model has many advantages such as strong pertinence, obvious physical meaning and more accurate life prediction, and has a very good application value..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 806001 (2011)
Measurement and Metrology
Research on Techniques of Fabrication and Measurement about Fizeau Infrared Interferometer
Yuan Qun, Gao Zhishan, Li Jianxin, Zhou Yuxuan, Chu Guang, and Shi Yang
A Fizeau infrared (IR) interferometer which can test the quality of aspheric surfaces and wavefront aberration of IR aspheric lens is designed and fabricated. The interferometer with aperture of 120 mm comprises F/1 and F/4 standard germanium lens. Two IR detectors are mounted on imaging paths for alignment and measurA Fizeau infrared (IR) interferometer which can test the quality of aspheric surfaces and wavefront aberration of IR aspheric lens is designed and fabricated. The interferometer with aperture of 120 mm comprises F/1 and F/4 standard germanium lens. Two IR detectors are mounted on imaging paths for alignment and measurement, which can be used to monitor orientations of standard lens and elements under test, coupled with raster ruler. The configuration solves the problems of adjustment brought by invisible characteristic of IR light. Phase shifter with great elongation is calibrated by technique of on-line calibration. The quality of IR aspheric lens is measured with the interferometer, and system errors of the interferometer are also tested. Results indicate that the accuracy and repeatability of the interferometer are better than 0.01λ (RMS) and 0.002λ (RMS), respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 808001 (2011)
Effect of Temperature Change on the Surface Accuracy of Bonded Lens
Wang Rudong, Tian Wei, Wang Ping, Wang Lipeng, Sui Yongxin, and Yang Huaijiang
In order to reduce the lens surface deformation when the temperature changes, the bonded lens can achieve better effect than the lens which is mounted by spacer and retainer. The radial stress of the bonded lens and surface deformation at 16 ℃, 20 ℃ and 26 ℃ are compared by theoretical calculation and simulation. ExperIn order to reduce the lens surface deformation when the temperature changes, the bonded lens can achieve better effect than the lens which is mounted by spacer and retainer. The radial stress of the bonded lens and surface deformation at 16 ℃, 20 ℃ and 26 ℃ are compared by theoretical calculation and simulation. Experiment is then made to prove that the surface deformation (PV value) of the bonded lens (0.073λ, 0.064λ, 0.085λ) is better than the mounted lens (0.204λ, 0.108λ, 0.105λ) at different temperatures. Finally, the error sources of the surface deformation about theoretical calculation, simulation and experiment at different temperatures are analyzed. Experimental results indicate that the surface accuracy of bonded lens is better than that of the mounted lens, and the bonded lens has less surface deformation when the temperature changes..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 808002 (2011)
Fringe Inverse Videogrammetry Based on Global Pose Estimation
Xiao Yongliang, Su Xianyu, and Chen Wenjing
Fringe inverse videogrammetry based on global pose estimation is presented. The camera pose is estimated with planar characteristic points extracted from fringes by Fourier analysis. The fringes are captured using camera with probe, and the coordinates of probe can be measured with the help of the camera pose. The cameFringe inverse videogrammetry based on global pose estimation is presented. The camera pose is estimated with planar characteristic points extracted from fringes by Fourier analysis. The fringes are captured using camera with probe, and the coordinates of probe can be measured with the help of the camera pose. The camera pose estimation is the key step in fringe inverse videogrammetry. The cost function for iterative pose estimation involves image-space error and object-space error, both having two local minima. The danger that the cost function converges to a local minimum can be avoided by use of global pose estimation. High-precision pose of camera can be obtained to accomplish the probe calibration and coordinate measurement. The experiments demonstrate that the method can measure the three-dimensional coordinates precisely..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 808003 (2011)
Precise Measurement of Dither Offset in Mechanical Dithered Ring Laser Gyro
Fan Zhenfang, Luo Hui, Lu Guangfeng, and Hu Shaomin
Using digital processing technique, a novel dither offset evaluation apparatus is designed for mechanical dithered ring laser gyro (MDRLG). Theoretical analysis shows that the dither offset can be obtained both from the absolute value and valid value of angle rate. The digital realizations of both the two apparatus areUsing digital processing technique, a novel dither offset evaluation apparatus is designed for mechanical dithered ring laser gyro (MDRLG). Theoretical analysis shows that the dither offset can be obtained both from the absolute value and valid value of angle rate. The digital realizations of both the two apparatus are introduced in detail. Simulations of them show that both the two apparatus can evaluate the dither offset even when the dither amplitude and dither frequency changes. Using the real time dither offset as the dither amplitude reference can achieve a better dither driving stability than using the feedback of piezoelectric transducer..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 808004 (2011)
Study of Cloud Droplet Probe and Its Calibration
Bu Lingbing, Wang Min, Huang Xingyou, Zhu Yazong, and Li Huilong
Probe of cloud droplet (CDP) based on forward scattering is one of the most important instruments for small cloud particles, smaller than 50 μm in diameter, measurement because of its high efficiency and simple structure. A CDP based on forward scattering is constructed. To measure the depth of field, a pinhole adheredProbe of cloud droplet (CDP) based on forward scattering is one of the most important instruments for small cloud particles, smaller than 50 μm in diameter, measurement because of its high efficiency and simple structure. A CDP based on forward scattering is constructed. To measure the depth of field, a pinhole adhered to a rotating disk which is fixed to multi-dimensional optical table is used to simulated as a particle appeared in the detection area periodically, as it moved along the laser beam, the depth of the field can be measured. Standard particles with size of 5, 10 and 30 μm are used to calibrate the system and the response curve to standard particles is obtained. Mie theory is used to study the corresponding relation between the system′s responses to standard particles and cloud droplet. The response curve to cloud droplets is obtained to measure the sizes of cloud droplets..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 808005 (2011)
Optical Communication
Research on Fabrication and Characteristic of Twin-Core Erbium-Doped Fiber
Liu Lisong, Ren Wenhua, Chen Weiguo, Peng Jian, and Jian Shuisheng
The fabrication of a twin-core erbium-doped fiber (TC-EDF) is reported. The twin-core erbium-doped fiber with single core doped is fabricated by modified chemical vapor deposition (MCVD) and photonic crystal technology. The characteristics of the twin-core erbium-doped fiber are numerically simulated by using coupled mThe fabrication of a twin-core erbium-doped fiber (TC-EDF) is reported. The twin-core erbium-doped fiber with single core doped is fabricated by modified chemical vapor deposition (MCVD) and photonic crystal technology. The characteristics of the twin-core erbium-doped fiber are numerically simulated by using coupled mode theory and rate equations. Meanwhile, a twin-core erbium-doped amplifier is established and measured experimentally. It is presented that this type of twin-core erbium-doped fiber is well fit for gain equalization..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 805001 (2011)
A New Phase Generated Carrier Demodulation Method Based on Fixed Phase Delay
Shi Qingping, Zhang Huayong, Wang Liwei, Tian Changdong, Zhang Min, Tian Qian, and Liao Yanbiao
In order to eliminate the effects of frequency modulation depth, signal phase delay and intensity accompanying modulation on phase generated carrier demodulation approach using orthogonal terms (OT-PGC), a new PGC method is proposed based on fixed phase delay (FPD-PGC) introduced by 3×2 directional coupler. The seIn order to eliminate the effects of frequency modulation depth, signal phase delay and intensity accompanying modulation on phase generated carrier demodulation approach using orthogonal terms (OT-PGC), a new PGC method is proposed based on fixed phase delay (FPD-PGC) introduced by 3×2 directional coupler. The second harmonics of two interferometric signals are used for demodulation. The demodulation principle of the new method is described in detail and its performances are studied. The harmonic suppression ratio (HSR) of the new method is increased by more than 30 dB compared with OT-PGC method under the condition of intensity accompanying modulation coefficient of 0.4 according to simulation. The signal-to-noise ratio (SNR) is also improved significantly. Experimental test shows the same result. Theoretical analysis and experimental results show that the new method eliminates the effect of signal phase delay and suppresses the impacts of frequency modulation depth and intensity accompanying modulation to a great extent..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 805002 (2011)
Jitter Performance of Clock Signal Extracted by Fiber Optical Parametric Oscillator with Low Power Pump
Luo Te, Wu Baojian, and Wen Feng
An optical return-to-zero (RZ) signal is generated from non-return-to-zero (NRZ) signal by means of two-stage optical modulation technique, and then is launched into the fiber parametric oscillator under low power pump for parametric wavelength conversion and clock extraction. Experiments show that, for 10 Gbit/s clockAn optical return-to-zero (RZ) signal is generated from non-return-to-zero (NRZ) signal by means of two-stage optical modulation technique, and then is launched into the fiber parametric oscillator under low power pump for parametric wavelength conversion and clock extraction. Experiments show that, for 10 Gbit/s clock extraction with 1.6 nm-interval wavelength conversion, the optimized input pump power is in the range of 8~14 dBm, the jitter suppression function can be implemented for the input signal with the amplitude and phase jitters of less than 2.28 mV and 3.5 ps, and the slopes of the corresponding input/output transfer curves are about 0.29 and 0.16, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 805003 (2011)
Influence of Time-Varying Atmospheric Turbulence to Facular Orientation Deviation in Dynamic Process
Shen Baoliang, Sun Jianfeng, Zhou Yu, Pu Lili, Li Bing, and Liu Liren
In order to study the influence of time-varying turbulence to facular orientation precision when the facula is moving during pointing and tracking process, a random phase screen is generated by using modified inverse Fourier transform to simulate the atmospheric turbulence. And then the orientation deviation of the facIn order to study the influence of time-varying turbulence to facular orientation precision when the facula is moving during pointing and tracking process, a random phase screen is generated by using modified inverse Fourier transform to simulate the atmospheric turbulence. And then the orientation deviation of the facular barycenter, the relation between the deviation and the facular position in the detector and the orientation precision of the facula are analyzed under different atmospheric turbulence intensities. The results indicate that there is a deviation between actual translational amount of the facular barycenter and that of the barycenter detected by the charge-coupled device in the presence of time-varying atmospheric turbulence, and it relates with the atmospheric turbulence intensity. And the orientation precision relates with both the atmospheric turbulence intensity and the facular position in the detector..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 805004 (2011)
Dynamic Demodulation of Fiber Bragg Grating Vibration Sensor Based on Cascaded Long-Period Fiber Grating
Zou Hongbo, Liang Dakai, Zeng Jie, Mu Hao, and Zhou Li
A dynamic demodulation method of fiber Bragg grating (FBG) vibration sensor based on cascaded long-period fiber grating (CLPG) is proposed. The light of broad optical source is reflected by FBG, then the reflected light entrances the CLPG. The intensity of reflected light of FBG changes after being modulated by CLPG. MA dynamic demodulation method of fiber Bragg grating (FBG) vibration sensor based on cascaded long-period fiber grating (CLPG) is proposed. The light of broad optical source is reflected by FBG, then the reflected light entrances the CLPG. The intensity of reflected light of FBG changes after being modulated by CLPG. Monitoring system is calibrated by temperature-measuring experiment firstly. Then FBG is stuck on the surface of aluminum specimen, and wavelength change of FBG caused by vibration of the aluminum specimen in low and high frequence is monitored by the system. The acquired vibration signal and fast Fourier transform (FFT) of the experiment data agree with the signal of eddy current displacement meter. It is shown that the FBG dynamic demodulation based on CLPG can be used to monitor no more than 2 kHz dynamic signal..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 805005 (2011)
Study on Parabolic Self-Similar Pulse Generation in a Nonlinearity Increasing Fiber
Li Liping, and Zhang Ailing
The self-similar evolution of an initial Gaussian pulse propagating in a nonlinearity increasing fiber (NIF) with an exponential nonlinearity profile is studied theoretically and numerically. As well as the dispersion decreasing fiber with normal group velocity dispersion (ND-DDF with a hyperbolic dispersion profile), The self-similar evolution of an initial Gaussian pulse propagating in a nonlinearity increasing fiber (NIF) with an exponential nonlinearity profile is studied theoretically and numerically. As well as the dispersion decreasing fiber with normal group velocity dispersion (ND-DDF with a hyperbolic dispersion profile), the NIF is also equivalent to a fiber amplifier, which can generate a parabolic self-similar pulse with strictly linear chirp. Furthermore, the impacts of two equivalent ways of ND-DDF and NIF on characteristics of the self-similar evolution are studied. The theoretical and simulation results show that: 1) the equivalent gain determines the results of self-similar evolution while the equivalent method determines the process speed; 2) with the same equivalent gain, the initial pulses in ND-DDF and NIF both evolve into the same parabolic self-similar pulse, but the process of NIF is more efficient, needing a shorter fiber length; 3) the relationship of fiber lengths of NIF and ND-DDF is to make the two fibers have the same “effective amplification”..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 805006 (2011)
Study of the Impact of LED Nonlinearity on Orthogonal Frequency Division Multiplex Based Visible Light Communication Systems
Yang Yu, Zhang Jiankun, Liu Bo, and Chen Hongda
From the light-emitting diode (LED) Shockley equation, a LED′s bidirectionally saturated nonlinearity model in visible light communication (VLC) system is established in conjunction with high power amplifier model which shows saturated behavior at very large input voltage. Monte Carlo simulations are conducted to an orFrom the light-emitting diode (LED) Shockley equation, a LED′s bidirectionally saturated nonlinearity model in visible light communication (VLC) system is established in conjunction with high power amplifier model which shows saturated behavior at very large input voltage. Monte Carlo simulations are conducted to an orthogonal frequency division multiplex (OFDM) based VLC system using the LED model. Manifold analyses suggest that the system performance deeply depends on some key parameters in respect of LED nonlinearity, direct current (DC) bias voltage, baseband modulation scheme, signal clipping ratio, and the manner in which the signal is clipped..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 805007 (2011)
Improvement of the Beam Quality Factor by Using Tapered Micro/Nano Fiber
He Hualong, Feng Guoying, Deng Guoliang, and Zhou Hao
The finite difference time domain method (FDTD) was used to research the influence of the micro/nano fiber on the beam quality. The micro/nano fibers were made by using fused-tapered technique. And using CCD, we have measured the beam propagation factors M2 of beams passing through the tapered micro/nano fiber and the The finite difference time domain method (FDTD) was used to research the influence of the micro/nano fiber on the beam quality. The micro/nano fibers were made by using fused-tapered technique. And using CCD, we have measured the beam propagation factors M2 of beams passing through the tapered micro/nano fiber and the single mode fiber, respectively. The experimental results indicated that, compared to the beam propagation factor M2 of beam propagating along the single mode fiber, M2 of beam propagating along the tapered micro/nano fiber is better. The experimental results are consistent with the FDTD calculation results..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 805008 (2011)
Measurement of Polarization Coupling and Analysis of Vibration Disturbance Signal
Guo Zhenwu, Zhang Hongxia, Jia Dagong, Chen Xinwei, and Liu Tiegen
The principle of the mode coupling in polarization maintaining fiber (PMF) is analyzed. The measurement method of polarization coupling based on white-light interferometry with Michelson-interferometer is presented. The optical path difference (OPD) between the two arms of Michelson interferometer, changed by the movemThe principle of the mode coupling in polarization maintaining fiber (PMF) is analyzed. The measurement method of polarization coupling based on white-light interferometry with Michelson-interferometer is presented. The optical path difference (OPD) between the two arms of Michelson interferometer, changed by the movement of the scanning arm reflector driven by a step motor, compensates the OPD of the two orthogonal beams resulting from polarization coupling to realize the measurement of polarization coupling intensity and the spatial distribution along the PMF. Analysis and emulation are carried out for the disturbance signal of the mechanical scanning vibration and the influence of the vibration imposed on the output signal. The coupling intensity is calculated from the envelope of the output signal which is extracted by Hilbert transform and least squares Gaussian fitting under different scanning speeds. It′s indicated that the vibration amplitude and frequency which affect the detection accuracy are related to the scanning speed. And the detection error reaches the minimum when the scanning speed of the system is from 0.7 to 0.9 mm/s..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 805009 (2011)
Optical Design and Fabrication
Optical System Design of a Two-Linear Array Stereoscopic Mapping CCD Camera
Chang Lingying, Zhao Baochang, Yang Jianfeng, and Wen Desheng
In order to obtain the image of 7 m resolution with the Chang′E-2 CCD stereoscopic camera on the 100-km-altitude circular orbit, a two-linear array CCD camera stereoscopic mapping optical system is designed. The principle of two-linear array stereo mapping camera is described. According to the satellite requirements, tIn order to obtain the image of 7 m resolution with the Chang′E-2 CCD stereoscopic camera on the 100-km-altitude circular orbit, a two-linear array CCD camera stereoscopic mapping optical system is designed. The principle of two-linear array stereo mapping camera is described. According to the satellite requirements, the main parameters of the optical system are calculated detailedly. The focal length of the system is 144.4 mm, the view angle is 42\O, the relative aperture is F/9, and the spectral range is 450~520 nm. The optical system adopts six groups of seven pieces type complicated double Gaussian structure with distortion elimination, for which the average modulation transfer function is 0.67 at 50 lp/mm Nyquist spatial frequency. The 100 km first rail images and polar region image of Chang′E-2 satellite CCD stereoscopic camera are obtained. The images are clear and rich of detail information, demonstrating the effectiveness of the optical system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 816001 (2011)
Spectroscopy
Study of X-Ray Backlight Imaging Based on Spherically Bent Quartz Crystal
Liu Lifeng, Xiao Shali, Wu Yufen, Qian Jiayu, Shi Jun, Liu Shenye, Wei Minxi, and Chen Bolun
In order to diagnose the distribution, stability, dimensions and plasma uniformity of pellet implosion in the inertial confinement fusion (ICF), an X-ray backlight imaging system based on spherically bent crystal has been set up using the X-ray Bragg diffraction theory. The primary component of the imaging system is thIn order to diagnose the distribution, stability, dimensions and plasma uniformity of pellet implosion in the inertial confinement fusion (ICF), an X-ray backlight imaging system based on spherically bent crystal has been set up using the X-ray Bragg diffraction theory. The primary component of the imaging system is the spherically bent α-quartz crystal which has characteristics of stability, complete structure, high reflectivity and resolution. The crystal dimension is 65 mm×20 mm and the curvature radius is 143.3 mm. Monochromatic X-ray backlight imaging experiment using the imaging system has been carried out. In the experiment, the object is a 3×3 array square stainless steel grid. It obtains two-dimensional monochromatic X-ray backlight image of chrome in imaging plane. The X-ray backlight imaging system based on spherically bent crystal provides an approximate 83.3 μm spatial resolution and a 9.6 mm×28.7 mm field of views. It is demonstrated that this backlight imaging system could be used for monochromatic X-ray backlighting imaging diagnosis..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 815001 (2011)
Laser-Induced Plasma Spectra of Heating Surface Materials with Different Hardnesses
Li Junyan, Lu Jidong, Li Jun, Yao Shunchun, and Dong Meirong
Laser-induced breakdown spectroscopy (LIBS) is used to analyze the properties of boiler heating surface materials. Ovenproof steel 12Cr1MoV is made to a series of samples with different hardnesses by heat treatment process. The appropriate spectral lines of the characteristic elements are selected and the impact of difLaser-induced breakdown spectroscopy (LIBS) is used to analyze the properties of boiler heating surface materials. Ovenproof steel 12Cr1MoV is made to a series of samples with different hardnesses by heat treatment process. The appropriate spectral lines of the characteristic elements are selected and the impact of different hardnesses on laser induced plasma properties of alloy steel is analyzed. Not only the relation between the hardness and the ionic to atomic spectral lines intensity ratio of a matrix element and three alloy steel elements, but also the relation between the hardness and the plasma temperature is analyzed. Experimental results show that the ionic to atomic spectral lines intensity ratio and plasma temperature increased with the increasing hardness, because the plasma shockwave characteristic and the ablation quality are different..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 815002 (2011)
Quantitative Determination of Heavy Metal Element Pb in Aqueous Solutions by Laser-Induced Breakdown Spectroscopy Using Paper Slice Substrates
Xiu Junshan, Hou Huaming, Zhong Shilei, Wang Zhennan, Lu Yuan, and Zheng Rong′er
In order to improve detection sensitivity and reproducibility of metal element analysis in aqueous solutions using laser induced breakdown spectroscopy (LIBS), a paper slice has been used as a liquid absorber to transform liquid sample analysis to solid sample analysis. Calibration curves for metal element Pb under difIn order to improve detection sensitivity and reproducibility of metal element analysis in aqueous solutions using laser induced breakdown spectroscopy (LIBS), a paper slice has been used as a liquid absorber to transform liquid sample analysis to solid sample analysis. Calibration curves for metal element Pb under different concentrations have been obtained. The results demonstrate that the analysis accuracy and error of detection limit produced by the internal standard method are more precise than those in absence of internal standard. Mn is chosen as the reference element. With optimized experimental parameters, such as the delay time for LIBS signal detection, gate width and pulse energy, the detection limit of Pb is determined to be 3.87 mg/L, which is lower than those obtained by similar detected methods. The detection sensitivity is about ten times higher than that in our previous experiments, in which the laser pulse is focused on the surface of the liquid jet. The paper sample is very easy to handle so that the detected time can be greatly shortened. As the lower pulse energy is needed, this approach provides a more practical approach for metal element analysis in aqueous solutions by using LIBS..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 38, Issue 8, 815003 (2011)
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