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2016
Volume: 43 Issue 8
35 Article(s)
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Beam Transmission and Control
Reduced-Scale Experiment of Beam Propagation Under Multilayer Atmosphere Model Along Inhomogeneous Turbulent Path
Shao Wenyi, and Xian Hao
To set the reasonable position distribution and the number of phase screens are crucial in the research on beam propagation along inhomogeneous turbulent path. A multilayer atmospheric optimization model is constructed based on the multilayer phase-screen model. Combined with an example of light propagation in two-layeTo set the reasonable position distribution and the number of phase screens are crucial in the research on beam propagation along inhomogeneous turbulent path. A multilayer atmospheric optimization model is constructed based on the multilayer phase-screen model. Combined with an example of light propagation in two-layer phase-screen model, both the boundary of atmospheric layers and the optimal position of phase screen are calculated under the condition of Hufnagel-Valley 5/7 atmospheric turbulence profile model. And the maximization of Rytov criterion in the two-layer phase screen model is introduced as well. The specific experimental parameters of the above-mentioned model are calculated according to the principles of equal Fresnel number, equal turbulence effect and reduced-scale principle. The experimental and the theoretical data on the probability density distribution of intensity fluctuation and the phase structure function are compared and analyzed. The results show that the trend of intensity fluctuation under different zenith angles is consistent with the lognormal distribution, and the empirical cumulative distribution function of intensity fluctuation in the experiment agrees basically with theoretical results, which indicates that the curve of its probability density distribution has a good fit degree. Although some errors exist in the phase structure functions between test results and theoretical calculation results in the low frequency region, it can be seen that the structure function still approximates a 5/3 power law..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 805001 (2016)
Laser Devices and Laser Physics
Coupling Method for Making Space Light into Single-Mode Fiber Based on Laser Nutation
Gao Jianqiu, Sun Jianfeng, Li Jiawei, Zhu Ren, Hou Peipei, and Chen Weibiao
Based on the theory of mode-field matching, the relationship between coupling efficiency and jitter amplitude, radius ratio of Airy disk and single-mode fiber mode field is analyzed. In order to reduce the effect of random angle jitter on coupling efficiency, an automatic coupling scheme for making space light into sinBased on the theory of mode-field matching, the relationship between coupling efficiency and jitter amplitude, radius ratio of Airy disk and single-mode fiber mode field is analyzed. In order to reduce the effect of random angle jitter on coupling efficiency, an automatic coupling scheme for making space light into single-mode fiber based on laser nutation is designed. The miss distance is calculated by data acquisition card and the offset voltage is output. The influence factors of algrithm precision and the relationship between laser nutation signal frequency and jitter frequency are analyzed. The feasibility of the algorithm is verified by Matlab simulation and experiments. Accuracy of miss distance angle is about 3 μrad obtained by experiment. The system feasibility is verified by space laser communication system. The coupling efficiency of the system is 67% when there is no disturbance, and it is improved by 6.5% when the disturbance is introduced and the control system is used to compensate the disturbance. The system response speed reaches 40 Hz. The coupling system is simple in structure and accurate in control algorithm. The controller signal processing speed is fast, and it has a great significance on the coupling of space light to single mode optical fiber..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 801001 (2016)
Timing and Carrier Envelope Phase Synchronization from Two Independent Femtosecond Lasers
Tian Haochen, Song Youjian, Ma Chunyang, Hu Minglie, and Wang Qingyue
We studied the timing and carrier envelope phase synchronization from two independent Yb-doped femtosecond lasers. With the balanced optical correlation method used, timing delay of the pulses from two lasers is detected. Two pulse trains are synchronized through controlling the piezoelectric transducer in one of the lWe studied the timing and carrier envelope phase synchronization from two independent Yb-doped femtosecond lasers. With the balanced optical correlation method used, timing delay of the pulses from two lasers is detected. Two pulse trains are synchronized through controlling the piezoelectric transducer in one of the laser cavities and the residual timing jitter is 380 as. Different repetition rate locking bandwidths yield different carrier envelope phase signal characteristics. Compared with using the piezoelectric transducer (narrow locking bandwidth), using the electro-optic modulator (wide locking bandwidth) leads excess noise to the carrier envelope phase during the repetition rate locking. The output of the two lasers is coincident in space, enters the balanced detector, and the relative carrier envelope frequency signal is detected. The carrier envelope phase is tightly locked by using an external cavity acousto-optic modulator, and the residual phase noise is 495 mrad. The spectrum coherence of the two lasers is achieved, which is the basis of coherent pulse synthesis..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 801003 (2016)
Nanosecond-Pulsed Yb-Doped Fiber Laser at 978 nm Based on Diode Laser Modulation Technique
Zhou Guanrui, Shi Hongxing, Jin Dongchen, Tan Fangzhou, Liu Jiang, Wang Qian, and Wang Pu
Based on diode laser modulation technique, a 978 nm nanosecond-pulsed Yb-doped fiber laser is designed. The structure of the laser is master oscillator power amplifier. The laser system consists of the seed of modulated laser diode and one stage Yb-doped fiber amplifier with single-mode and single-cladding. The spectraBased on diode laser modulation technique, a 978 nm nanosecond-pulsed Yb-doped fiber laser is designed. The structure of the laser is master oscillator power amplifier. The laser system consists of the seed of modulated laser diode and one stage Yb-doped fiber amplifier with single-mode and single-cladding. The spectral central wavelength of laser diode seed is set as 978.3 nm by self-seeding. The laser pulse width after modulation is 4.5 ns and the repetition frequency is tunable at 10~50 MHz. The seed light is amplified to 115 mW by one stage Yb-doped fiber amplifier with single-cladding when the repetition frequency of laser diode seed modulation is 50 MHz. The corresponding central wavelength of the laser is 978.3 nm, 3 dB spectral bandwidth is 0.11 nm. The obvious amplified spontaneous emission does not appear in the spectrum after amplification..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 801005 (2016)
Analysis of Natural Longitudinal Mode Selection in Passively Q-Switched Lasers
Chen Suyuan, Yang Hailong, Wang Mingjian, Zhang Xin, Jiang Jing, Meng Junqing, and Chen Weibiao
An analytical expression is developed for the difference in buildup time between two adjacent longitudinal modes in a passively Q-switched laser resonator. The probability of single-frequency operation of both the small gain and the initial inversion population being several times greater than the threshold inversion cAn analytical expression is developed for the difference in buildup time between two adjacent longitudinal modes in a passively Q-switched laser resonator. The probability of single-frequency operation of both the small gain and the initial inversion population being several times greater than the threshold inversion can be predicted. A Cr4+YAG-passively Q-switched NdYAG laser set-up with 11 cm cavity length is used to carry out a series of experiments to verify the theoretical predictions. Experimental results support the probability of single mode operating based on adjacent longitudinal mode buildup-time difference, and the laser system can operate stably at single mode without any intra-cavity mode selecting elements in a long time in certain temperature range..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 801006 (2016)
Mode-Locked Regenerative Amplifier Based on Single Mode Fiber
[in Chinese], Logan Wright, [in Chinese], and Frank Wise
The dynamic evolution of the mode-locked regenerative amplifier based on single mode fiber, which is also called pulse-based start-up dissipative soliton mode-locked laser, is numerically simulated, and the evolutions of the pulse energy, pulse duration, and spectral bandwidth versus the cycling number of the incident The dynamic evolution of the mode-locked regenerative amplifier based on single mode fiber, which is also called pulse-based start-up dissipative soliton mode-locked laser, is numerically simulated, and the evolutions of the pulse energy, pulse duration, and spectral bandwidth versus the cycling number of the incident pulse in the cavity are analyzed. By using an electro-optic modulator in the cavity, the input pulses can be successfully injected into the cavity for circulation. With the demonstration of the timing sequence of the modulator, the laser runs steadily for 13 roundtrip. Meanwhile, when the circulation roundtrip is fixed at 2, the influence of the pump power on the output spectrum is investigated. The final output laser pulse has a spectral bandwidth of 60 nm and single-shot pulse energy of 20 nJ. Besides, the reason that the output pulse energy is limited in the mode-locked regenerative amplifier based on a single mode fiber is also analyzed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 801007 (2016)
Experimental Research of Direct Writting Short Cavity Lasers in Er/Yb Co-Doped Fibers
Song Zhiqiang, Wang Weitao, Qi Haifeng, Peng Gangding, and Wang Chang
The short cavity fiber lasers with distributed feedback and distributed Bragg reflection structures are fabricated by using direct ultraviolet exposure on the photosensitive Er/Yb co-doped single mode fibers respectively produced in Nufern and CorActive companies. The experimental results show that the quenching effectThe short cavity fiber lasers with distributed feedback and distributed Bragg reflection structures are fabricated by using direct ultraviolet exposure on the photosensitive Er/Yb co-doped single mode fibers respectively produced in Nufern and CorActive companies. The experimental results show that the quenching effect related to temperature exists in the Er/Yb co-doped fibers. In the process of laser slope efficiency test, the laser output power suddenly falls down when the pump power reaches certain value. But when an auxiliary heat dissipation is given to the laser resonant cavity, the laser conversion efficiency increases by certain value. The successive power measurement results of the same laser show that the laser efficiency measured later is always lower than that measured just after its fabrication. Moreover, the output power decline at high pump power and the temperature-sensitive situation always exist..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 801008 (2016)
Comparative Investigation of Electromagnetic Pulses Generated by Strong Laser Irradiating Planar and Hohlraum Targets
Yang Ming, Yi Tao, Yang Jinwen, Wang Chuanke, Li Tingshuai, Liu Shenye, Jiang Shao′en, and Ding Yongkun
By designing pulsed receiving antennas and optimizing test methods, the relationship between laser parameters, such as intensity distribution of electromagnetic pulses (EMPs) from SGIII prototype laser facility and target type is established, which can provide an experimental basis for further investigating EMP generatBy designing pulsed receiving antennas and optimizing test methods, the relationship between laser parameters, such as intensity distribution of electromagnetic pulses (EMPs) from SGIII prototype laser facility and target type is established, which can provide an experimental basis for further investigating EMP generation mechanism and laser-target interaction. Based on the consideration of the polarization direction uncertainty of electromagnetic fields, three mutual orthogonal magnetic loop antennas are selected to measure the EMP signal inside the target chamber of the laser facility. A comparative analysis on the frequency features of the EMP signals from two kinds of targets is conducted, and the influence of antenna position on the signal strength is discussed. At the same time, the distribution of EMPs inside the spherical chamber is analyzed by multi-physics simulation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 801009 (2016)
Design and Implementation of Miniaturized Frequency-Stabilized Laser System with Low Power Consumption
Yu Qi, Xiong Wei, Zhang Yin, Chen Xuzong, and Duan Xiaohui
We designed and realized a compact laser system of which the frequency can be automatically stabilized. The laser system can operate with low power consumption and long-term stability. The power consumption and the volume of the system are reduced through our designed voltage source with high efficiency and low ripple.We designed and realized a compact laser system of which the frequency can be automatically stabilized. The laser system can operate with low power consumption and long-term stability. The power consumption and the volume of the system are reduced through our designed voltage source with high efficiency and low ripple. With the high-performance temperature controller, current controller and automatic frequency stabilization modules, a laser with narrow linewidth and high frequency stability is realized. The linewidth is about 1 MHz, and the frequency stabilities at 1, 10, 100, 1000 s are 1.43×10-10, 3.90×10-11, 1.28×10-11, 2.25×10-11, respectively. Compared with the commercial external-cavity diode lasers, the designed system has better long-term frequency stability. The volume of the power supply for the system is reduced by 85%, and the power consumption is reduced by 90%. The system is a new scheme for realizing low power consumption and miniaturization of the frequency-stabilized semiconductor laser system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 801010 (2016)
A Stress Fiber Sensor Based on Laser Beat Frequency
Wang Xu, Zhang Haojie, Wen Quan, Chen Longfei, Wang Fang, and Liu Yufang
Combining the characteristics of linear chirped fiber Bragg grating (CFBG), a stress fiber sensor based on laser beat frequency is designed. Using the method of CFBG converting the wavelength change into the length change of resonant cavity, the wavelength demodulation is achieved. The proposed method is different fromCombining the characteristics of linear chirped fiber Bragg grating (CFBG), a stress fiber sensor based on laser beat frequency is designed. Using the method of CFBG converting the wavelength change into the length change of resonant cavity, the wavelength demodulation is achieved. The proposed method is different from previous methods changing the cavity length. The group delay of linear CFBG is measured and the system structure and principle are described in detail. Besides, the measuremental results and precision are analyzed and calculated. The length change of cavity can reach 6.2 cm, which accounts for 2.55% of total cavity length. The results show that the strain measurement precision can be up to 10-7 N..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 801011 (2016)
Laser Manufacturing
Superhydrophobic Titanium Surface Micro/Nanostructures Induced by Femtosecond Laser
Pan Huaihai, Wang Zhuo, Fan Wenzhong, Wang Chengwei, Li Hongjin, Bai Feng, Qian Jing, and Zhao Quanzhong
A method to fabricate superhydrophobic titanium (Ti) surface using linearly polarized femtosecond pulsed laser is proposed in this paper. A femtosecond pulsed laser is used to irradiate Ti surfaces to scan and induce the surface micro/nanostructures, so as to improve the surface roughness. The superhydrophobicity of thA method to fabricate superhydrophobic titanium (Ti) surface using linearly polarized femtosecond pulsed laser is proposed in this paper. A femtosecond pulsed laser is used to irradiate Ti surfaces to scan and induce the surface micro/nanostructures, so as to improve the surface roughness. The superhydrophobicity of the Ti surfaces is realized by combing ultrasonic treatment of low surface energy material. The roughnesses of Ti surfaces are changed by tuning the energy flux density of femtosecond pulsed laser irradiation, and different wettabilities of Ti surfaces are realized. The fabricated Ti surfaces with hydrophobicity and superhydrophobicity are placed in atmosphere for three months, and the wettabilities of the surfaces are measured. The results show that the wettabilities of the surfaces are nearly the same after three months, namely the fabricated Ti surfaces still exhibit stable hydrophobicity and superhydrophobicity..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 802002 (2016)
Parameter Identification of Constitutive Model at High Strain Rate for TC17 Titanium Alloy Under Shock Wave Induced by Nanosecond Pulsed Lasers
You Xi, Nie Xiangfan, He Weifeng, and Li Donglin
On the basis of the Johnson-Cook (J-C) constitutive model, one parameter identification method based on the finite element model and the modified Levenberg-Marquard (L-M) algorithm is proposed. When TC17 materials are under laser shocking with different parameters and processes, the residual stress field distribution aOn the basis of the Johnson-Cook (J-C) constitutive model, one parameter identification method based on the finite element model and the modified Levenberg-Marquard (L-M) algorithm is proposed. When TC17 materials are under laser shocking with different parameters and processes, the residual stress field distribution at high strain rate is obtained and the dynamic response curve at intermediate strain rate is obtained by the Hopkinson pressure bar. The above two test results are taken as the targets of identification. The response curve at low strain rate is introduced as a constraint condition and the J-C constitutive model parameters at high strain rate are identified. The comparison between the experimental and calculated results indicates that the parameters obtained by identification can be used to accurately describe the dynamic response law of TC17 titanium alloys at high strain rate and to predict the residual stress field distribution of materials under laser shocking..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 802003 (2016)
Calculation of Argon-Aluminum Interatomic Potential and Its Application in Molecular Dynamics Simulation of Femtosecond Laser Ablation
[in Chinese], [in Chinese], [in Chinese], and Shih Cheng-Yu
When molecular dynamics method is used to simulate femtosecond laser ablation of aluminum (Al) in argon (Ar) environment, the interaction of Ar and Al atoms needs to be considered. The potential function of Ar-Al interaction is obtained by combining two types of potential functions, including short range and long rangeWhen molecular dynamics method is used to simulate femtosecond laser ablation of aluminum (Al) in argon (Ar) environment, the interaction of Ar and Al atoms needs to be considered. The potential function of Ar-Al interaction is obtained by combining two types of potential functions, including short range and long range. The molecular dynamics simulation results of femtosecond laser ablation at corresponding small system and scale are given by using the interaction potential. Ziegler-Biersack-Littmark (ZBL) potential function is used in shorter range of Ar-Al interatomic potential. Lennard-Jones (LJ) potential function is used in longer range. Second-order polynomial is used at the intermediate distance. The parameters of LJ potential function are obtained by fitting the Ar-Al binding energy. The Ar-Al interatomic potential function is used in molecular dynamics simulation of femtosecond laser ablation of aluminum in argon environment. The ablation dynamic images under picosecond time delay and the evolution laws of temperature and density of Ar in the process are obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 802004 (2016)
Effect of UPPLW on Grain Size of Laser Welding Joints of TC4 Titanium Alloy
Liu Haodong, Hu Fangyou, Cui Aiyong, Dai Jingtao, Huang Fei, and Li Hongbo
In order to improve the laser welding quality of TC4 titanium alloy, a technology named ultrasonic processing across different phases based on laser welding (UPPLW) is introduced. With the three-circle-cutoff-point method, the effect of ultrasonic vibration field power on the microstructures of laser welding joints is In order to improve the laser welding quality of TC4 titanium alloy, a technology named ultrasonic processing across different phases based on laser welding (UPPLW) is introduced. With the three-circle-cutoff-point method, the effect of ultrasonic vibration field power on the microstructures of laser welding joints is studied by changing the intensity of ultrasonic vibration field, and the measured data are analyzed based on the reliability theory. The results show that, under the influence of the ultrasonic vibration field, with the increase of ultrasonic vibration power, the microstructure grain of the welding joints has a tendency to be progressively refined. When the power is 1600 W, the grain is refined by about 15.8% compared with that obtained with conventional methods. The mechanism for UPPLW to refine grain is finally analyzed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 802005 (2016)
Temperature and Thermal Stress Analysis of Aluminium Alloy Plate Irradiated by Long Pulsed Laser
Wang Yibin, Jin Guangyong, and Zhang Wei
Based on the von Mises yield criterion and the elastoplastic constitutive relation, a spatial axisymmetric finite element model is established for long pulsed laser irradiating 7A04 aluminium alloys, and the temperature field and the thermal stress field are calculated by the finite-element/finite-difference hybrid algBased on the von Mises yield criterion and the elastoplastic constitutive relation, a spatial axisymmetric finite element model is established for long pulsed laser irradiating 7A04 aluminium alloys, and the temperature field and the thermal stress field are calculated by the finite-element/finite-difference hybrid algorithm when the laser beam with a Gaussian intensity profile heating the aluminium alloy plate. It is found that the Mises stress on the target surface distributes mainly within a certain scope around the center. At a position far from the center, the Mises stress is very small which barely affects the target and the Mises equivalent stress is far less than the yield strength of the aluminum alloy target. The consistency between the simulation and experimental results confirms the validity of the model..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 802006 (2016)
Numerical Simulation of Residual Stress Field Induced in Round Rod Part Affected by Laser Parameters
Wang Jingxue, Zhang Yan, Zhang Xingquan, Qi Xiaoli, Pei Shanbao, and Chen Bin
A three dimensional finite element model is established to estimate the residual stress field induced by single laser shock processing (LSP) in aluminum alloy round rod part. The simulation results are consistent with the experimental results. The effect of laser parameters including laser power density, shock angle anA three dimensional finite element model is established to estimate the residual stress field induced by single laser shock processing (LSP) in aluminum alloy round rod part. The simulation results are consistent with the experimental results. The effect of laser parameters including laser power density, shock angle and shock times on residual stress field is systematically investigated with the aid of the established model. The results show that during the laser shocking of round rod, larger laser power density causes smaller compressive residual stress in the central spot area. The compressive residual stress in the center area turns into tensile residual stress with the increase of laser power density, and increases with the increasing shock angle. Moreover, the compressive residual stress at the spot center increases significantly under certain impact times and gradually reaches saturation. The plastically affected depth increases with the increase of laser power density and shock times, and is almost not affected by the shock angle..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 802007 (2016)
Spectral Analysis of Laser Induced Plasma Electrical Signals from NdYAG Laser Welding of A304 Stainless Steels
Yang Ruixia, Yang Lijun, Liu Tong, and Zhao Shengbin
The electrical signals of laser induced plasma from NdYAG laser welding of A304 stainless steels are detected by a passive electrical probe. The relationship between different laser welding modes and the spectral analysis results of plasma electrical signals are investigated. The waveforms and spectra of plasma electriThe electrical signals of laser induced plasma from NdYAG laser welding of A304 stainless steels are detected by a passive electrical probe. The relationship between different laser welding modes and the spectral analysis results of plasma electrical signals are investigated. The waveforms and spectra of plasma electrical signals are analyzed. The relationship between the formation characteristic of laser welds under different laser welding modes and the waveforms and spectra of the plasma electrical signals is illustrated. The results indicate that, under the specified conditions in the experiments, different laser welding modes correspond to different spectral characteristics of plasma electrical signals. Moreover, whether the welding mode is a deep penetration one or not can be identified by the spectral intensity E of plasma electrical signals within the scope of 500～1000 Hz. When E is large enough or exceeds a certain value, the laser welding mode is a deep penetration welding..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 802008 (2016)
Microstructure Evolution of Heat-Affected Zones of 28CrMoNiV Steel Repaired by Lasers
Li Yundong, Dong Gang, and Yao Jianhua
A laser cladding test on a 28CrMoNiV substrate by a 3 kW broadband semiconductor laser is conducted, and the refabrication process is optimized with the aid of simulation of the temperature fields in the areas of heat-affected zones (HAZ). By means of optical microscope, scanning electron microscope, and X-ray diffractA laser cladding test on a 28CrMoNiV substrate by a 3 kW broadband semiconductor laser is conducted, and the refabrication process is optimized with the aid of simulation of the temperature fields in the areas of heat-affected zones (HAZ). By means of optical microscope, scanning electron microscope, and X-ray diffraction, the microstructures in the HAZ and substrate zone are studied. The tensile test is conducted to investigate the tensile performance of the repaired laser cladding HAZ. The results show that, in the HAZ of the single-layer cladding sample, there exists a martensite phase transformation and an undesirable microstructure composed of martensite and δ-ferrite distributes at the top of the HAZ. The simulation results indicate that this undesirable microstructure can be eliminated if the over-three-layer cladding is adopted. The tensile testing results show that the HAZ with three-layer cladding has the average tensile strength up to 927.35 MPa, which is higher than those of the substrate or the HAZ with single-layer cladding. The average fractural elongation of the HAZ with three-layer cladding is 10.23%, which is a little higher than that of the single-cladding and much closer to that of the substrate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 802009 (2016)
Microscopic Structure and Tensile Property of Laser Melting Deposited TA15/Ti2AlNb Dual Alloy
Chen Yiqiang, Liu Yantao, Tang Yangjie, and Zhang Yongzhong
Thin wall TA15/Ti2AlNb dual alloy samples are prepared on the TA15 alloy substrate by using laser melting deposition technology. The microscopic structure and phase composition of as-deposited and heat treated TA15/Ti2AlNb dual alloy are analyzed, respectively, and the mechanical property of dual alloy at room temperatThin wall TA15/Ti2AlNb dual alloy samples are prepared on the TA15 alloy substrate by using laser melting deposition technology. The microscopic structure and phase composition of as-deposited and heat treated TA15/Ti2AlNb dual alloy are analyzed, respectively, and the mechanical property of dual alloy at room temperature is tested. The results show that the as-deposited TA15/Ti2AlNb dual alloy possesses a good mechanical performance with a tensile strength of 1096 MPa, an elongation of 5.2%, and the fracture position is located in the transition zone. In contrast, as for the heat treated dual alloy, the tensile strength is 1053 MPa, the elongation is 3.2%, and the fracture position is located in the TA15 alloy side. As for the as-deposited TA15/Ti2AlNb dual alloys, the variation of the phase from the TA15 side to the Ti2AlNb side is in the order of α and β two-phase, α, α2 and β/B2 three-phase, α2, β/B2 and O three-phase, α2, B2 and O three-phase..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 802010 (2016)
High-Temperature Tensile Property of GH4169 Nickel-Based Superalloys by Laser Repair
Zhao Jianfeng, Cheng Cheng, Xie Deqiao, and Xiao Meng
Laser repair of GH4169 alloy which is commonly used in aero engines by usage of the nickel-based superalloy FGH95 powder is tested. The high-temperature tensile properties of the repaired sample with different process parameters are investigated and the fracture mechanism is also analyzed. The results show that, with aLaser repair of GH4169 alloy which is commonly used in aero engines by usage of the nickel-based superalloy FGH95 powder is tested. The high-temperature tensile properties of the repaired sample with different process parameters are investigated and the fracture mechanism is also analyzed. The results show that, with appropriate process parameters, the high-temperature tensile strength of the repaired samples can be recovered up to more than 85% of that of the intact samples. When the laser linear energy density is 100 J/mm2, the maximum high-temperature tensile strength is 708 MPa, which is 90.4% of that of the intact sample and the maximum yield strength is 538 MPa, which exceeds 4.3% of that of the intact sample. The fractions of the repaired samples occur at the substrate heat-affected zone, where the segregation of elements is induced by the alternating heat action of laser scanning. This segregation is the main reason for the degradation of the high-temperature tensile property of the repaired samples..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 802012 (2016)
Study on Tribology Performance of CoCrMo Alloy Parts Manufactured by Selective Laser Melting
Zhang Guoqing, Yang Yongqiang, Lin Hui, Song Changhui, Zhang Zimian, and Yu Jiakuo
The friction wear testing machine is applied in the friction and wear experiments and the weight of the parts before and after experiments are compared in order to investigate the variance of friction coefficients and wear rates under different conditions. In order to study the wear mechanism, the surface structure andThe friction wear testing machine is applied in the friction and wear experiments and the weight of the parts before and after experiments are compared in order to investigate the variance of friction coefficients and wear rates under different conditions. In order to study the wear mechanism, the surface structure and morphology of CoCrMo parts before and after experiments are observed by the metalloscope and the scanning electron microscope, respectively. The results show that, under the respective lubrication condition of dry friction, sodium chloride (NaCl) or artificial saliva, the wear rate of the front face of the SLM manufactured parts is 27.92%, 21.15% or 19.03% lower than that of the casting parts, and 26.97%, 10.88% or 14.97% lower than that of the lateral face. Compared with casting parts, the SLM manufactured parts have a uniform surface structure on which there nearly no holes. Under the condition of dry friction, abrasive wear dominates. In contrast, under the lubrication conditions of NaCl and artificial saliva, abrasive wear and fatigue wear dominate. These findings provide the basis for the application of the SLM manufactured CoCrMo alloy in medical implants..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 802013 (2016)
Molecular Dynamics Simulation of Plastic Deformation of Pure Titanium Under Shock Loading
Chen Yazhou, Zhou Liucheng, He Weifeng, Luo Sihai, Jiao Yang, Pang Chengqing, and Liu Peng
Laser shock peening utilizes the mechanical effect of shockwave to improve the mechanical properties of metal materials, however, it is very difficult to measure the dynamic physical parameters after shockwave, the local dynamic mechanical parameters, and the development of microstructure with current means of experimeLaser shock peening utilizes the mechanical effect of shockwave to improve the mechanical properties of metal materials, however, it is very difficult to measure the dynamic physical parameters after shockwave, the local dynamic mechanical parameters, and the development of microstructure with current means of experiment. The molecular dynamics method is employed to conduct the shock simulation in pure titanium at a starting temperature of 300 K , the dynamic dual-wave structure feature of the shockwave in pure titanium under the shock loading is observed, and the change of the mechanical parameters as well as the dynamic growing process of twin phase under shock loading are obtained. During the plastic deformation, the stoppage and release of dislocation make the normal stress rise while the shear stress and von Mises stress continue to drop, and the parallel twin gratings are formed. A layer of amorphous structure is observed on the surface subject to shock loading, and its formation is related to ultrahigh strain rate plastic deformation and dynamic recrystallization behavior. Both the twin structure and the amorphous structure coincide with the results obtained by transmission electron microscopy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 802014 (2016)
Microstructure and Property of Nb-Al-Ti High Temperature Alloy Coatings by Laser Cladding on Ti Alloy Surfaces
Shan Xiaohao, Wang Cunshan, and Yu Qun
By the laser cladding technique, the Nb-Al-Ti high temperature alloy coatings with different Ti contents are prepared on the TC4 alloy surfaces, and the influence of Ti contents on the microstructure, hardness and high temperature oxidation resistance property of alloy coatings is investigated. The results show that, wBy the laser cladding technique, the Nb-Al-Ti high temperature alloy coatings with different Ti contents are prepared on the TC4 alloy surfaces, and the influence of Ti contents on the microstructure, hardness and high temperature oxidation resistance property of alloy coatings is investigated. The results show that, with the increment of Ti addition, the microstructure develops from β-(Nb,Ti) dentrite+interdendritic Nb3Al to β-(Nb,Ti) dentrite+interdendritic Nb3Al+Nb2Al, which results in an increase in microhardness. Under the influences of the intermetallic compounds quantity and microsegregation, the high temperature oxidation resistance of alloy coatings is optimal with a Ti addition of 15.18%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 802015 (2016)
Materials and Thin Films
CO2 Laser Power Delivery Characteristics of Ge-Sb-Se Glass Fibers
Yan Chunyang, Wu Lihua, Dai Shixun, Zhang Peiqing, Liu Zijun, and Wang Xunsi
Ge20Sb15Se65 chalcogenide glasses with low impurity absorption are prepared and fibers with different diameters are drawn. The power delivery characteristics of CO2 laser (10.6 μm) through these fibers are experimentally investigated. The experiment results show that the glass prepared has good anti-crystallization proGe20Sb15Se65 chalcogenide glasses with low impurity absorption are prepared and fibers with different diameters are drawn. The power delivery characteristics of CO2 laser (10.6 μm) through these fibers are experimentally investigated. The experiment results show that the glass prepared has good anti-crystallization property, and the infrared transmission in the 5-11 μm band is about 64%. Under high power CO2, heat accumulation caused by the light absorption makes the temperature on the fiber end surface rise rapidly, and the melting damage is observed on the end surface of the Ge20Sb15Se65 glass fiber. The maximum output power of 809 mW with the input power of 5267 mW is obtained by using the fiber with a diameter of 800 μm. The output power density is 161 W/cm2 and the delivery efficiency is 16%. The experimental results are basically consistent with the theoretical calculation results..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 803001 (2016)
Measurement and Metrology
Impact Localization by Using Fiber Bragg Grating Sensors Based on Correlation Dimension
Xiong Zhili, Liang Dakai, Li Tongwei, Shi Lu, and Jia Hongyu
Aiming at the requirement of low speed impact localization, a fiber Bragg grating (FBG) sensor network is constructed. Distribution of the correlation dimension as well as the distance between the impact point and the sensor are studied, taken the correlation dimension with the impact response signal time series as an Aiming at the requirement of low speed impact localization, a fiber Bragg grating (FBG) sensor network is constructed. Distribution of the correlation dimension as well as the distance between the impact point and the sensor are studied, taken the correlation dimension with the impact response signal time series as an impact characteristic. Based on this distribution, the impact load position is regionally identified; the coordinated localization conducted by tri-circle model is achieved. The wing box structure is divided into several areas, where the configuration of FBG sensors is optimized according to the algorithm characteristics. As a result, the impact monitoring system is built and the low speed impact test is carried on. The result shows that the ten testing random impact points on the 30 cm×30 cm wing box plate structure are all identified correctly with an average error of 3.5 cm. The impact load position identification using six FBG sensors is effectively realized in this method, providing a reference for combination of fractal theory with impact monitoring technology..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 804001 (2016)
Optical Communication
Mode Demultiplexing Based on Cascaded Independent Component Analysis for Mode Division Multiplexing System with High Mode Group Delay
Fang Yan, Hu Guijun, Gong Caili, and Li Li
Aiming at the mode division multiplexing system with high-mode group delay (H-MGD) using few-mode fiber, a cascaded independent component analysis (C-ICA) algorithm is proposed. The core idea of the algorithm is that two complex ICA algorithms are combined with a delay compensation module to eliminate the modal crosstaAiming at the mode division multiplexing system with high-mode group delay (H-MGD) using few-mode fiber, a cascaded independent component analysis (C-ICA) algorithm is proposed. The core idea of the algorithm is that two complex ICA algorithms are combined with a delay compensation module to eliminate the modal crosstalk induced by the mode multiplexer and the demultiplexer respectively. Then the proposed C-ICA algorithm is utilized to demultiplex the received signals from a 2×2 mode division multiplexing system, and the demultiplexing performance of C-ICA is compared with that of the common ICA in which the complex ICA algorithm is used only once. The simulation results indicate that the proposed C-ICA algorithm can implement mode demultiplexing of the mode division multiplexing system with H-MGD few-mode fiber validly. Moreover, C-ICA has better mode demultiplexing performance than the common ICA under the same conditions..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 806001 (2016)
Research on Channel Characteristics of High-Precision Frequency Remote Transmission via Optical Fiber
Li Dongjin, Mei Jinjie, Hu Dengpeng, and Ren Tianpeng
The loss of stability of frequency remote transmission problems caused by fiber channel characteristics is studied. The unstability is introduced by integrated fiber thermal expansion, refractive instability distribution and dispersion effects characteristic changing with temperature. A link delay model is established.The loss of stability of frequency remote transmission problems caused by fiber channel characteristics is studied. The unstability is introduced by integrated fiber thermal expansion, refractive instability distribution and dispersion effects characteristic changing with temperature. A link delay model is established. 1550 nm signal transmission experiment through the 25 km single mode fiber model is validated. Experimental results show that the theoretical calculated delay variation and experimental results of the model stay consistent, when the optical fiber temperature and environmental temperature change synchronized and other environmental factors have little effect on the stability of the transmission. The model is discussed and the changes of model parameters caused by temperature and wave length are determined, and the order of magnitudes of various features introduced to delay is obtained. When the relative delay caused by changes of refractive index change turns to 10.22 ns, the fiber thermal expansion and dispersion effects caused delays are 0.7741 ns and -0.5983 ps respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 806002 (2016)
Bandwidth of Adaptive Optics System in Satellite-Ground Coherent Laser Communication
Li Jiawei, and Chen Weibiao
The influence of system bandwidth of adaptive optics system to communication performance is investigated for satellite-ground coherent opticscommunication. For a certain modes corrected by adaptive optics, the required servo bandwidth is obtained and the low earth orbit (LEO) satellite-ground laser links are compared wThe influence of system bandwidth of adaptive optics system to communication performance is investigated for satellite-ground coherent opticscommunication. For a certain modes corrected by adaptive optics, the required servo bandwidth is obtained and the low earth orbit (LEO) satellite-ground laser links are compared with the geosynchronous (GEO) satellite-ground laser links. The results show that the LEO links require larger servo bandwidth than the GEO links. This is due to the high speed relative movement between the LEO and the ground station can generate vertical wind speed link. And the bandwidth requirement of adaptive optics system for LEO-ground link and zenith angle are inversely related. The relationship between the mixing efficiency LEO-ground coherent laser communication link, the adaptive optics system servo bandwidth and corrected modes is also studied. The results show that 200 Hz of close-loop bandwidth can meet the requirement, and increasing the number of actuators on deformable mirror is a more effective way to improve the mixing efficiency when the bandwidth reaches 100 Hz..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 806003 (2016)
Rapid Communications
[in Chinese]
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Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 815001 (2016)
[in Chinese]
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 815002 (2016)
Reviews
Ultrafast Laser Fabricated Bio-Inspired Surfaces with Special Wettability
Long Jiangyou, Fan Peixun, Gong Dingwei, Zhang Hongjun, and Zhong Minlin
Bio-inspired surfaces with special wettability include superhydrophilic surfaces and various kinds of superhydrophobic surfaces. Since these surfaces possess the properties as self-cleaning, anti-icing, anti-drag, and so on, they have attracted tremendous attentions of international academia in recent years. With the rBio-inspired surfaces with special wettability include superhydrophilic surfaces and various kinds of superhydrophobic surfaces. Since these surfaces possess the properties as self-cleaning, anti-icing, anti-drag, and so on, they have attracted tremendous attentions of international academia in recent years. With the rapid development of ultrafast lasers, various surfaces with special wettability can be fabricated by means of the ultrafast laser. Compared to other methods, the ultrafast laser surface treatment technology is simple, flexible and controllable. The research progress in combination with the research achievements in our group in this field is reviewed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 800001 (2016)
Remote Sensing and Sensors
Analysis of Effect of Ambient Temperature Variation on Measurement Accuracy of Shack-Hartmann Wavefront Sensor
Meng Qingbin, Qi Yuejing, Lu Zengxiong, Su Jiani, and Gao Fei
Ambient temperature variation is one of the key factors that affect the measurement accuracy of Shack-Hartmann wavefront sensor (SHWS). The influence of the distortion of micro-lens array (MLA) and the refractive index variation, the distance changes between MLA and charge coupled device(CCD), and the distance change bAmbient temperature variation is one of the key factors that affect the measurement accuracy of Shack-Hartmann wavefront sensor (SHWS). The influence of the distortion of micro-lens array (MLA) and the refractive index variation, the distance changes between MLA and charge coupled device(CCD), and the distance change between spherical point source and SHWS on measurement accuracy of SHWS are analyzed by using the thermal analysis function of Zemax software, which is caused by ambient temperature variation. The analysis and calculation show that the main factor affecting the measurement accuracy of SHWS is the distance change between MLA and CCD caused by ambient temperature variation. The measurement error is 0.52 nm root mean square(RMS) when the ambient temperature rises every 1 ℃ from 21 ℃ to 24 ℃. The experiments of testing the measurement accuracy of SHWS are carried out by using a nearly perfect spherical wave generated by single mode optical fiber diffraction. The results obtained from simulation and experiment are basically identical..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 810001 (2016)
Distributed Feedback Fiber Laser Hydrophone Used in Flank Array
Tang Bo, Huang Junbin, Gu Hongcan, and Mao Xin
To reduce the fluctuation of a distributed feedback (DFB) fiber laser used in underwater sound detection, a fiber laser hydrophone of encapsulated structure with two diaphragms is designed. This structure increases the activated area of the acoustic pressure through the diaphragms, which is transformed to the axial strTo reduce the fluctuation of a distributed feedback (DFB) fiber laser used in underwater sound detection, a fiber laser hydrophone of encapsulated structure with two diaphragms is designed. This structure increases the activated area of the acoustic pressure through the diaphragms, which is transformed to the axial strain in the fiber laser to realize the enhancement of the pressure sensitivity. After the structure is analyzed by ANSYS, the prototypes of the new kind of hydrophone based on the structure are fabricated and tested. Experimental results show that acoustic pressure sensitivity of the DFB fiber laser hydrophone reaches to -136.9 dB with the fluctuation less than ±0.5 dB in the frequency range of 2.5~10 kHz, which shows that the working frequency of the hydrophone is expanded to high frequency and it can well meet the requirements for the engineering application of flank array..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 810002 (2016)
Effective Lidar Ratio of Cirrus Cloud Measured by Three-Wavelength Lidar
Ji Chengli, Tao Zongming, Hu Shunxing, Zhang Xuehai, Liu Dong, Wang Zhenzhu, Zhong Zhiqing, Xie Chenbo, Yuan Ke′e, Cao Kaifa, Huang Jian, and Wang Yingjian
The simulation study is conducted based on Mie scattering theory as well as the relationship between the cirrus extinction characteristics, the effective lidar ratio and wavelengths. Data of observation is measured to calculate the effective lidar ratios of different wavelengths by three-wavelength lidar system in the The simulation study is conducted based on Mie scattering theory as well as the relationship between the cirrus extinction characteristics, the effective lidar ratio and wavelengths. Data of observation is measured to calculate the effective lidar ratios of different wavelengths by three-wavelength lidar system in the western suburbs of Hefei from January 2011 to October 2012. Both the theoretical and experimental results show that in regard to the three wavelengths 355,532,1064 nm, the extinction coefficient of cirrus cloud is independent of the wavelengths, and the effective lidar ratio increases as the wavelength increases. The effective lidar ratio of cirrus cloud in Hefei ranges from 10~70 sr, and the mean value of three-wavelength is (21.0±9.3) sr, (29.4±11.7) sr and (38.1±11.4) sr. The effective lidar ratio of cirrus cloud measured by 355 nm wavelength is the lowest in autumn, while that measured by 532 nm and 1064 nm are the highest in autumn..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 810003 (2016)
Spectroscopy
Highly Efficient Measurement Technology Based on Hyper-Spectropolarimetric Imaging
Xue Peng, Wang Zhibin, Zhang Rui, Wang Yaoli, and Liu Shun
In order to acquire the full Stokes parameters in the new hyper-spectropolarimetric imaging system quickly and accurately, which is filtered by the acousto-optic tunable filter (AOTF) and modulated by the liquid crystal variable retarder (LCVR), we propose a new measurement method that two LCVRs are controlled by one dIn order to acquire the full Stokes parameters in the new hyper-spectropolarimetric imaging system quickly and accurately, which is filtered by the acousto-optic tunable filter (AOTF) and modulated by the liquid crystal variable retarder (LCVR), we propose a new measurement method that two LCVRs are controlled by one driving signal source, and we take four fixed driving voltages in turn when the LCVR phase modulation is carried out under different wavelengths. The full Stokes parameters about incident light via the corresponding mathematical calculation are obtained. In order to verify the accuracy of this method, we take three polaroids with the polarization directions of 0°, 90°, and 45° respectively and a quarter-wave plate as the target, with a sheet of frosted glass as the background. Images of all the Stokes parameters are obtained by the imaging system. The results show that the proposed method can obtain all Stokes parameters with high imaging quality. In addition, we further verify the feasibility of the system and the accuracy of the method with the aid of hyper-spectropolarimetric imaging of true leaves and false leaves with different colors. The factors that influence the measurement accuracy of Stokes parameters are analyzed theoretically, providing a theoretical basis for further improving measurement accuracy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 43, Issue 8, 811001 (2016)
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