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Contents
2015
Volume: 42 Issue 7
48 Article(s)
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Research Article
Measurement of Thickness Uniformity of Optic Multilayer Based on Surface Figure Measurement
In order to evaluate the multilayer thickness uniformity of the optics, the measurement method based on optic figure reproducibility metrology is studied. The process of uniformity measurement and the influence factors are analyzed, and the measurement errors due to the reproducibility metrology are evaluated. The finiIn order to evaluate the multilayer thickness uniformity of the optics, the measurement method based on optic figure reproducibility metrology is studied. The process of uniformity measurement and the influence factors are analyzed, and the measurement errors due to the reproducibility metrology are evaluated. The finite element analysis (FEA) model of the multilayer is built and the optic figure error due to the inner stress of the multilayer is calculated. The uniformity measurement is carried out on the high reproducibility metrology device, and the results indicate that the multilayer thickness uniformity of the optic in clear aperture is better than 0.1 nm (root mean square). When the results are transformed to thickness profile along the radial points on the optic and compared with the reflectometry test results it is shown that, the uniformity results based on reproducibility metrology are reliable. The experimental results verify the feasibility and the practicability of the measurement method of the multilayer thickness uniformity..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 708010 (2015)
Fidelity in a System of a Moving Two-Level Atom Interacting with Polya State Light for Multi-photon Transition
Wang Yanqing, Sachuerfu, and Wang Yanan
The fidelity in a system which is composed of a multi- photon transition moving two- level atom interacting with Polya state light is studied by means of the full quantum theory. The influences of the atomic initial state, field-mode structure parameter, the maximum photon number of the light, the optical field parametThe fidelity in a system which is composed of a multi- photon transition moving two- level atom interacting with Polya state light is studied by means of the full quantum theory. The influences of the atomic initial state, field-mode structure parameter, the maximum photon number of the light, the optical field parameters and the values of the transitional photon number on the fidelity of the system are also analyzed .The results show that the velocity of atom effects the oscillation period of fidelity. The fidelity presents different patterns when transitional photon numbers are at some fixed values..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 718001 (2015)
High Power Electric-Discharge Non-Chain Pulsed DF Laser
Pan Qikun, Xie Jijang, Shao Chunlei, Shao Mingzhen, Wang Chunrui, Zhang Laiming, and Guo jin
The studies of a repetitively pulsed deuterium fluoride (DF) laser based on electric-discharge and closed cycle are presented. Using double-pressure tank circuit and a rough cathode, the self-sustained volume discharge of 1.65 L is obtained in SF6-D2 mixtures. A centrifugal fan provides adequate gas flow to refresh mixThe studies of a repetitively pulsed deuterium fluoride (DF) laser based on electric-discharge and closed cycle are presented. Using double-pressure tank circuit and a rough cathode, the self-sustained volume discharge of 1.65 L is obtained in SF6-D2 mixtures. A centrifugal fan provides adequate gas flow to refresh mixture gas quickly. The gases pass through a scrubber cell in which ground state DF molecules are eliminated from the gas stream. The influences of gas parameters and charging voltages on the output characteristics of non-chain pulsed DF laser are investigated experimentally. At the charging voltage of 43 kV, under the optimum working condition (the working gas ratio is 8:1, the total pressure is 8.1 kPa), a maximum output energy of 3.46 J, an electro-optical conversion efficiency of 3.12% and a pulsed width of 135 ns are got. At an operating repetition rate of 50 Hz, a maximum average output power of 150 W is obtained, whose amplitude difference of laser pulses is less than 8% . The far-field divergence angles in horizontal and vertical directions are 7.92 mrad and 9.58 mrad, respectively. 22 P-branch transition lines are achieved using DF laser spectrum analyzer. The result show that the pulsed electric-discharge DF laser is an effective technology to obtain high power mid-infrared laser..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 702001 (2015)
Study on Periodic Ripples on Metallic Surfaces Induced by Polarized Lasers
Tang Yanfu, and Nie Zhenwei
There are many studies on phenomenon of periodic ripples induced by polarized lasers on the surface of metal, but studies on mechanism are few. Femtosecond laser is polarized through inserting a quarter waveplate into the beam path, and then vertically transmitted onto the surface of tungsten to produce ripples. And thThere are many studies on phenomenon of periodic ripples induced by polarized lasers on the surface of metal, but studies on mechanism are few. Femtosecond laser is polarized through inserting a quarter waveplate into the beam path, and then vertically transmitted onto the surface of tungsten to produce ripples. And then the mechanism of the inducing ripples and influence of polarization of laser on the inducing ripples is studied. It is found that periodic ripples have a good correspondence with polarization of femtosecond laser. When the quarter waveplate rotates periodically of single direction, the polarization of femtosecond laser andthe direction of periodic ripples change accordingly. The maximum inclining angle of ripples is about π/4 . An analysis of the mechanism of matter that direction of ripples changes along with rotating of quarter waveplate is given. Theoretical analyses indicate that the direction of periodic ripples induced by polarized laser is primary decided by electricity vector components grown at the moment of laser flies across birefringent crystals, for example a quarter waveplate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 702002 (2015)
Molecular Dynamics Simulation of Dislocation Development in Monocrystalline Copper induced by Warm Laser Peening
Meng Xiankai, Zhou Jianzhong, Huang Shu, Sheng Jie, Su Chun, and Yang Xiangwei
In order to study the microstructure of face center cubic metals induced by thermo-mechanical impact, molecular dynamics method was used to investigate the dislocation evolution of monocrystalline copper treated by warm laser peening (WLP). The effects of plastic strain on the dislocation development were researched thIn order to study the microstructure of face center cubic metals induced by thermo-mechanical impact, molecular dynamics method was used to investigate the dislocation evolution of monocrystalline copper treated by warm laser peening (WLP). The effects of plastic strain on the dislocation development were researched through centrosymmetry parameter. Moreover, the effects of temperature on the dislocation development induced by plastic strain during WLP were also investigated. Finally, the strengthening effects of WLP were analyzed by work hardening. It is shown that partial dislocation and stacking faults are induced by plastic strain in the way of“vacancy group-partial dislocation-stacking faults”. As the plastic strain increases, the amount of stacking faults and their stacking extent increases, which leads to a better effect of WLP in work hardening. A higher temperature can promote the nucleation and development of dislocations induced by WLP. The hardening effect of WLP increases with the temperature within 200 ℃, and the hardening effect reduces while it increases to 250 ℃ because of the dislocation annihilation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 702003 (2015)
Electric and Magnetic Spectral Stokes Singularities of Partially Coherent Gaussian Vortex Beams
Luo Yamei, Tang Bihua, Gao Zenghui, and Lü Baida
Taking the paraxial Gaussian vortex beam as an example, the variation of magnetic spectral Stokes singularities of partially coherent beams is studied at the source plane and compared with electric spectral Stokes singularities of partially coherent beams. It is shown that at the source plane there exists magnetic and Taking the paraxial Gaussian vortex beam as an example, the variation of magnetic spectral Stokes singularities of partially coherent beams is studied at the source plane and compared with electric spectral Stokes singularities of partially coherent beams. It is shown that at the source plane there exists magnetic and electric spectral Stokes singularities of partially coherent Gaussian vortex beams. By suitably varying the beam waist width and off-axis parameter, the motion, creation, and annihilation of magnetic and electric spectral Stokes singularities will take place. In comparison with the electric spectral Stokes singularities of partially coherent beams, they do not coincide and the topological charges are not the same. But there exists a certain symmetry, and in the process, they satisfy the topological relation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 702004 (2015)
High-Efficiency Beam Combination of Continuous-Wave Quantum Cascade Lasers
Wu Hao, Shu Shili, Liu Fengqi, Ning Yongqiang, Wang Lijun, and Tong Cunzhu
In order to acquire high optical power for practical applications, technologies of beam combination which have been applied to semiconductors in near-infrared band successfully can also be employed to quantum cascade lasers (QCLs). The coplanar arrangement of QCLs is discussed which is helpful to maintain stable and reIn order to acquire high optical power for practical applications, technologies of beam combination which have been applied to semiconductors in near-infrared band successfully can also be employed to quantum cascade lasers (QCLs). The coplanar arrangement of QCLs is discussed which is helpful to maintain stable and reliable continuous-wave room-temperature operation of QCLs. In the experiment of collimation for a single QCL, collimated beams with beam quality factor M2 less than 2.3 are achieved. In the experiment of high-efficiency beam combination, the efficiency of 85% is achieved..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 702005 (2015)
Generation of Few-Cycle Femtosecond Pulses via Coherent Synthesis Based on Self-Frequency-Shifted Solitons in All-Solid-State Photonic Bandgap Fiber
Peng Tianduo, Liu Bowen, Zhang Juhui, Hu Minglie, Chai Lu, and Wang Qingyue
The synthesis of a nearly four-optical-cycle (14 fs) laser pulse from the coherent combination of dual femtosecond laser pulses with a femtosecond amplifier system is reported. The simulation confirms that the scheme is a viable method to produce few-cycle optical pulses. A Yb3+-doped femtosecond laser fiber amplifier The synthesis of a nearly four-optical-cycle (14 fs) laser pulse from the coherent combination of dual femtosecond laser pulses with a femtosecond amplifier system is reported. The simulation confirms that the scheme is a viable method to produce few-cycle optical pulses. A Yb3+-doped femtosecond laser fiber amplifier generates 62 fs transform-limited pulses with 1040 nm central wavelength. These pulses are split in two. One is employed as fundamental soliton pulses, the other is coupled into all-solid-state photonic bandgap fiber. The parameters are optimized such as the input power to obtain the 55 fs near transform- limited self- frequency- shifted solitons centered at 1150 nm wavelength. A nearly four-optical-cycle (14 fs) laser pulse is combined via coherent synthesis of the fundamental soliton and the self-frequency-shifted soliton..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 702006 (2015)
Multi-Photon Time-of-Arrival Resolution Enhancement by Deconvolution in Laser Ranging
Xue Li, Li Ming, Li Xiyu, and Wang Liangliang
Avalanche photo diodes (APDs) are parallel connected in multi pixel photon counter (MPPC). The output pulse is distorted when photon arrival time gets closer, and discrete photon arrival time is unable to resolve. With photon distribution and output pulse considered, analytical form of discrete photon arrival time deteAvalanche photo diodes (APDs) are parallel connected in multi pixel photon counter (MPPC). The output pulse is distorted when photon arrival time gets closer, and discrete photon arrival time is unable to resolve. With photon distribution and output pulse considered, analytical form of discrete photon arrival time detected in laser ranging is derived with deconvolution from the output pulse. Also, ranging data size is increased, helpful for the recognition of efficient photons from noise. In the algorithm, single pulse response is approximated to Gaussian form, and effects of time jitter on photon discrimination are studied. Consumed the time jitter of pulse response is 50~250 ps, both statistical distribution histogram and the relation of peak-valley contrast, time interval and time jitter are obtained with three photons. Data sizes before and after deconvolution are compared in kHz laser ranging system during 1 s observation time. Results show discrete time is able to be resolved when peak-valley contrast is above 10 in histogram, and the discrimination time resolution is 0.2~0.7 ns..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 702007 (2015)
Frequency Drift Measurement on Single-Frequency Laser by Short Fiber Delayed Self-Heterodyne
Duan Hongcheng, Wu Jin, Zhao Zhilong, and Wu Shudong
Based on delayed self-heterodyne and phase unwrapping techniques, a new approach to measure the frequency drift of a single-frequency laser by adopting relatively shorter fiber delay lines is proposed. The working principle and factors affecting the measurement accuracy of this method are given in theory. A laser that Based on delayed self-heterodyne and phase unwrapping techniques, a new approach to measure the frequency drift of a single-frequency laser by adopting relatively shorter fiber delay lines is proposed. The working principle and factors affecting the measurement accuracy of this method are given in theory. A laser that we can get the function of the frequency fluctuation easily is used to test the presented method. The experimental result demonstrates that the actual curve between laser frequency and time can be acquired accurately by this method. Then the frequency drift characteristic of a 1550 nm wavelength laser is measured by this method with a 6 m fiber delay line in 3 h continuously, resulting in the long-term frequency drift of 75 MHz/h, which is consistent basically with the nominal frequency stability 50 MHz/h..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 702008 (2015)
Investigation of Mode Competition in Dual-Frequency Nd∶YVO4 Microchip Laser
Hu Miao, Sun Xiao, Li Qiliang, Zhou Xuefang, Ying Na, Wei Yizhen, Lu Yang, Yang Guowei, Zheng Yaoyuan, and Wei Mian
The mode competition coupling effect between two laser modes in double-longitudinal-mode dualfrequency microchip lasers is investigated, and the self-saturation coefficient and cross saturation coefficient of the two laser mode in dual-frequency laser intra-cavity with different refletivities of output mirror are ascerThe mode competition coupling effect between two laser modes in double-longitudinal-mode dualfrequency microchip lasers is investigated, and the self-saturation coefficient and cross saturation coefficient of the two laser mode in dual-frequency laser intra-cavity with different refletivities of output mirror are ascertained by experiments. The dual-frequency microchip laser rate equation is established in the research, as the two variables of self-saturation coefficient β and cross saturation coefficient θ are undetermined. Thus the comparison of dualfrequency output power which is obtained by simulation is well illustrated by changing the parameters of microchip laser cavity. By comparing the power envelop profile with dual-frequency laser power spectrum, the two undetermined coefficients are confirmed. The experimental results show that with the refletivities of output mirror at 86%, 81% and 61% respectively, the corresponding self-saturation coefficients are 0.68, 0.66 and 0.52, which means the smaller the reflectivity of output mirror is, the stronger the two mode competition is. A high reflectivity of output mirror indicates the mode competition between the two modes is week, and a large frequency offset of dualfrequency laser can be obtained in such a case..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 702009 (2015)
3.2 ns High Peak Power Radially Polarized Pulsed Output from Passively Q-Switched Microchip Laser with Composite Structure of YAG/Nd∶YAG/Cr4+∶YAG Crystal
Han Xiahui, Xia Kegui, Li Guiyun, and Li Jianlang
High peak power radially polarized laser pulse is obtained from a passively Q-switched microchip laser with composite structure of YAG/Nd∶YAG/Cr4 +∶YAG crystal and photonic crystal grating mirror as the polarization-selective output coupler. The average output power is 435 mW and a slope efficiency is 15.7%. The laser High peak power radially polarized laser pulse is obtained from a passively Q-switched microchip laser with composite structure of YAG/Nd∶YAG/Cr4 +∶YAG crystal and photonic crystal grating mirror as the polarization-selective output coupler. The average output power is 435 mW and a slope efficiency is 15.7%. The laser pulse output has a maximum peak power of 15.7 kW, a minimum pulse duration of 3.2 ns, and repetition rate of 8.1 kHz at absorbed pump power of 6.5 W. The polarization degree of the radially polarized pulse is measured to be as high as 95.8% . All of the crystals in the experiment are <111> cut which is more beneficial for this laser to improve the uniformity of output radially polarized beam..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 702010 (2015)
Investigation on Spectral Purity of Injection Seeding Single Frequency Pulsed Optical Parametric Oscillator
Jiang Jiaxin, Li Shiguang, Ma Xiuhua, Liu Jiqiao, Zhu Xiaolei, and Chen Weibiao
Injection seeding single frequency pulsed optical parametric oscillator (OPO) is an important technique to realize differential absorption lidar, whose spectral purity effects the energy absorption of laser pulses travelling via atmosphere directly and influences the accuracy of lidar system. Spectral purity demonstratInjection seeding single frequency pulsed optical parametric oscillator (OPO) is an important technique to realize differential absorption lidar, whose spectral purity effects the energy absorption of laser pulses travelling via atmosphere directly and influences the accuracy of lidar system. Spectral purity demonstrates the ratio of seed mode energy to the whole pulse energy, which presents a comprehensive projection of spectral performances such as linewidth and frequency stability. In connection with 1.57 μm injection seeding OPO, factors influencing spectral purity are analyzed theoretically. A measuring system based on long path absorption cell is designed and built up. Experimental results show that spectral purity of injection seeding OPO can achieve 99.9% when seed injection power is 26 mW and OPO output energy is around 1.1 mJ..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 702011 (2015)
Application of an Er:Doped Fiber Comb for Sr Lattice Clock
Meng Fei, Cao Shiying, Zhao Guangzhen, Zhao Yang, and Fang Zhanjun
For measurement of the 87Sr lattice clock probe laser frequency and controlling the red cooling laser and lattice magic wavelength etc, a frequency comb based on a mode-locked erbium fiber laser is built and locked to H-maser. The measurement realizes strong output at desired wavelengths, including 689, 698 and 813 nm For measurement of the 87Sr lattice clock probe laser frequency and controlling the red cooling laser and lattice magic wavelength etc, a frequency comb based on a mode-locked erbium fiber laser is built and locked to H-maser. The measurement realizes strong output at desired wavelengths, including 689, 698 and 813 nm (acquire at different time in one branch). The total visible spectrum power is about 120 mW and the power in the single frequency is more than 200 μW within 2 nm (full width half maximum). The beat signal between the comb tooth and the external laser with a signal-to-noise ratio is up to 30 dB (300 kHz resolution bandwidth). The tracking stability is better than 60 mHz at 1 s..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 702012 (2015)
Effect of Different Process Temperatures on Residual Stress and Nano-Hardness of Warm Laser Peened INl718 Superalloy
Zhou Jianzhong, Han Yuhang, Huang Shu, Sheng Jie, Meng Xiankai, Zhang Haifeng, and Xu Suqiang
Warm laser peening process (WLP) is an innovative processing technique, which combines the advantages of laser peening (LP) and dynamic strain aging (DSA). In order to study the effect of different process temperatures on the thermal surface stability of WLP IN718, the LP(25 ℃) IN718 and WLP(230 ℃, 260 ℃, 290 ℃, 320 ℃ Warm laser peening process (WLP) is an innovative processing technique, which combines the advantages of laser peening (LP) and dynamic strain aging (DSA). In order to study the effect of different process temperatures on the thermal surface stability of WLP IN718, the LP(25 ℃) IN718 and WLP(230 ℃, 260 ℃, 290 ℃, 320 ℃ ) IN718 are served as the research objects. From the view points of compressive residual stress, nanohardness and elasticity modulus, the effects of different process temperatures on the thermal surface stability of WLP IN718 are explored by thermal insulation test and nano-indentation test. The results show that the compressive residual stress presents an decreasing trend with increasing the WLP temperature. LP and WLP samples thermal relaxation amplitude increase significantly with increasing the applied temperature, and the WLP samples have a better performance. WLP (260 ℃) IN718 has a best performance on thermal stability and nano-hardness, and the load-displacement curve further evidences the effect of temperature on thermal relaxation of WLP IN718 superalloy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 703001 (2015)
Patterning of Graphene by Femtosecond Laser Cutting
Lin Zhe, Ye Xiaohui, Han Jinpeng, Fan Peixun, and Zhong Minlin
With the continuous study of graphene, patterned graphene becomes the important requirement of graphene device application. The graphene patterned by femtosecond laser cutting is researched. The laser energy density and scanning speed influence the quality of graphene pattern, which is characterized by optical microscoWith the continuous study of graphene, patterned graphene becomes the important requirement of graphene device application. The graphene patterned by femtosecond laser cutting is researched. The laser energy density and scanning speed influence the quality of graphene pattern, which is characterized by optical microscope and Raman spectrometer. The threshold of laser energy density for monolayer graphene and multilayer graphene are determined to be 1.0 J/cm2 and 0.8 J/cm2, respectively, while the optimal scanning speed is 100 mm/s. By analyzing the Raman spertra of residual graphene in the laser scanning area, the mechanism of laser cutting is considered to be oxidized ablation. Basing on the optimal laser parameters, the complex patterning of graphene is achieved by controlling the laser beam movement. The method mentioned in this study provides a powerful support for graphene devices..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 703002 (2015)
Contrasting Study on Quality of SUS301L-HT Jointsin Fiber Laser Welding and MIG Welding
Tang Duo, Wang Chunming, Tian Man, Wang Jun, and Hu Xiyuan
Fiber laser welding and metal-inert gas (MIG) welding of SUS301L-HT sheets with 2 mm thickness are carried out, and differences in welding formation, microstructure and mechanical properties between two types of joints are researched and compared. Welding formation of two types joints is different from each other, and Fiber laser welding and metal-inert gas (MIG) welding of SUS301L-HT sheets with 2 mm thickness are carried out, and differences in welding formation, microstructure and mechanical properties between two types of joints are researched and compared. Welding formation of two types joints is different from each other, and formation of laser welding joint is better than that of MIG welding joint. Stable and uniform welding formation is acquired in fiber laser welding process and almost no angular distortion is found in laser welding joint and width of beads and heat affected zone (HAZ) is narrow. Microstructure of laser welding joints is quite different from that of MIG welding joint. Microstructure of laser welding bead consists of fine columnar austenitic dendritic crystals and interdendritic δ ferrite, and size of grain grows a little in HAZ; phase composition of MIG welding bead contains massive austenitic and a little δ ferrite, and microstructure in HAZ gets different obviously as distance from fusion line changes. Mechanical properties of two types joints are different. Tensile property of laser welding joint is much better than that of MIG welding joint. Tensile sample of laser welding joint breaks at bead, in tensile experiment, in a classical ductile way, ductility of the joint is up to 48.2%, and tensile strength is up to 979.1 MPa..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 703003 (2015)
Effect of Heat Input on Weld Joints Microstructure and Nano Mechanical Properties of Nano Precipitation Hardening Steel
Wang Haisheng, Wang Wei, Wang Xiaonan, Zhu Guangjiang, Chen Changjun, Zhang Min, and Zhu Guohui
Influence of heat input on the penetration, microstructure and nano mechanical properties of laser welding joint is studied. The penetration and microstructure of joints are tested by stereo microscope and scanning electron microscope. The nanohardness and elastic modulus of joints are tested by nanoindentation. The reInfluence of heat input on the penetration, microstructure and nano mechanical properties of laser welding joint is studied. The penetration and microstructure of joints are tested by stereo microscope and scanning electron microscope. The nanohardness and elastic modulus of joints are tested by nanoindentation. The result shows that the penetration increases with the increase of heat input, there is a linear relationship between penetration and heat input. Microstructure of weld seam is consist of full martensite when the heat input is below 94 J/mm2. Bainite and ferrite appear in the weld seam when the heat input is over 125 J/mm2, the volume of bainite and ferrite increases with the increase of heat input. With the increase of the welding heat input the nanohardness decreases gradually, the reason for the decrease is the formation of bainite and ferrite. The influence of welding heat input on the elastic modulus is not obvious, the modulus of elasticity is around 200 GPa..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 703004 (2015)
Molecular Dynamics Simulation of Plastic Deformation of Polycrystalline Cu under Mechanical Effect with Ultrahigh Strain Rate
Wang Zhilong, Luo Kaiyu, Liu Yue, and Lu Jinzhong
Laser shock processing utilizes mechanical effect with ultrahigh strain rate to generate deeper residual compressive stress and grain refinement layer, which improves mechanical properties, such as fatigue resistance, wear resistance and corrosion resistance. To date, it is very difficult to present dynamic microstructLaser shock processing utilizes mechanical effect with ultrahigh strain rate to generate deeper residual compressive stress and grain refinement layer, which improves mechanical properties, such as fatigue resistance, wear resistance and corrosion resistance. To date, it is very difficult to present dynamic microstructure evolution at ultra- short time (several ten nanoseconds) during the plastic deformation at ultrahigh strain rate using experimental method. At temperature of 300 K, a molecular dynamics of polycrystalline Cu with a loading duration of 15 ns at a strain rate of 2×107 s-1 is conducted to describe the microstructure evolution process with the LAMMPS soft. Under the mechanical effect of laser shock wave with a ultra-high strain rate, deformation twinning is the important microstructure of grain refinement of the alloys with medium stacking fault energy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 703005 (2015)
Simulation of Temperature Field for Laser Etching of Aluminum Thin Films on Polyimide Substrate
Liu Xiaoli, Xiong Yuqing, Yang Jianping, Wang Rui, Wu Gan, and Ren Ni
In order to study 1064 nm laser etching mechanism for aluminum thin films on polyimide substrate, the etching process of aluminum thin films is simulated by finite element analysis software ANSYS. By analyzing the laser energy absorbing and transforming process within aluminum thin films, temperature field distributionIn order to study 1064 nm laser etching mechanism for aluminum thin films on polyimide substrate, the etching process of aluminum thin films is simulated by finite element analysis software ANSYS. By analyzing the laser energy absorbing and transforming process within aluminum thin films, temperature field distribution of thin films induced by laser ablation is obtained, and the separation mechanism of aluminum thin films from polyimide substrate resulted by the decomposability of polyimide is verified..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 703006 (2015)
Optimal Design of Multidimensional Optical System for WBC Five Classification
Wan Lixia, Long Wei, Zhao Xiongfeng, Li Fugui, and Luo Liang
Traditional five classification hematology analyzers usually improve white blood cell (WBC) classification accuracy by combining chemical methods, which will increase the complexity of instrument structure and the cost of use and repair. An optical system with a special structure is designed, which introduces the detecTraditional five classification hematology analyzers usually improve white blood cell (WBC) classification accuracy by combining chemical methods, which will increase the complexity of instrument structure and the cost of use and repair. An optical system with a special structure is designed, which introduces the detection of back scattered light by the means of combining direct current (DC) signal, laser forward scattering signal and back scattering signal to achieve the WBC five classification. The experiment results show that the relative deviation of the prototype with the sensing system for LYM, MON, NEU, EOS and BAS is less than 5%, and its performance is close to the hematology analyzer Mythic 22. The optical system after optimization can complete in situ detection and classification of WBC and has the characteristics of simple structure and stable performance..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 704001 (2015)
Experimental Study of Tunable Pulse Duration Ho∶YAG Laser-Induced Liquid Jet
Lü Tao, Zhang Wei, and Chen Fang
High speed liquid jet from the nozzle of one closed vessel can be formed, which is urged by vaporization effect induced by fiber-transmitting infrared pulse lasers. The signals of water-jet pressure and shock wave pressure under various laser parameters and stand-off distances (d: distance between the end of optical fiHigh speed liquid jet from the nozzle of one closed vessel can be formed, which is urged by vaporization effect induced by fiber-transmitting infrared pulse lasers. The signals of water-jet pressure and shock wave pressure under various laser parameters and stand-off distances (d: distance between the end of optical fiber and the nozzle exit) are detected by two polyvinylidene fluoride (PVDF) needle hydrophones and are recorded by one oscilloscope. The relationship between water-jet pressure, shock wave pressure and pulse duration, laser energy is analyzed. The experimental result indicates that there is a positive correlation between water-jet pressure and pulse duration (494~967 μs) when the laser energy is 426.3 mJ. Contrarily, the relationship between shock wave pressure and pulse duration is negative when d is 2 cm or 4 cm. However, for d=6 cm the shock wave pressure increases firstly and decreases afterwards, and reaches a maximum value of 1.32 MPa when the pulse duration is 736 μs. Both water jet pressure and shock wave pressure increase in proportion to pulse energy (266.3~420.8 mJ) when the pulse duration is 480 μs. When the laser parameters are invariable, jet pressure and shock wave pressure all increase with increase of d..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 704002 (2015)
All-Optical Thresholder Based on Nonlinear Optical Loop Mirror
Li Qiang, Wang Zhi, Wu Chongqing, Wang Fu, Sun Zhenchao, Le Yansi, and Liu Lanlan
An all-optical thresholder based on the nonlinear optical loop mirror (NOLM) and the self-phase modulation (SPM) of photonic crystal fibers (PCF) which can be used in photonic neuron is achieved. The nonlinear coefficient of PCF is 16.98 (W·km)-1, while a tunable isolator into the NOLM is also introduced. Due to tAn all-optical thresholder based on the nonlinear optical loop mirror (NOLM) and the self-phase modulation (SPM) of photonic crystal fibers (PCF) which can be used in photonic neuron is achieved. The nonlinear coefficient of PCF is 16.98 (W·km)-1, while a tunable isolator into the NOLM is also introduced. Due to the use of highly nonlinear PCF and tunable isolator, it requires shorter cavity length and lower input power. By using the alloptical thresholder, optical signal extinction ratio can improve more than 6 dB. All devices in the all-optical threshoder are passive, therefore it is good for high speed optical signals. The all-optical thresholder also has broad application for other optical communication systems..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 705001 (2015)
Time Synchronization Technique for Joint Time and Frequency Transfer via Optical Fiber
Cheng Nan, Chen Wei, Liu Qin, Xu Dan, Yang Fei, Gui Youzhen, and Cai Haiwen
A time calibration and synchronization technique for joint time and frequency transfer via optical fiber is described. The time synchronization scheme for joint time and frequency transfer based on optical compensation technique and dense wavelength division multiplexer (DWDM) is theoretically analyzed. The verificatioA time calibration and synchronization technique for joint time and frequency transfer via optical fiber is described. The time synchronization scheme for joint time and frequency transfer based on optical compensation technique and dense wavelength division multiplexer (DWDM) is theoretically analyzed. The verification experiment is achieved via 50 km optical fiber spool in the laboratory, the accuracy of time synchronization is 1.6 ps. The time synchronization via 110 km urban fiber link is described, whose accuracy is 30.0 ps. The source of the error of the synchronization is analyzed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 705002 (2015)
Research on the Objective Function of Spatial Light Modulator-Based Output Spot Focusing for Multimode Fiber
Yin Zhe, Liu Guodong, Liu Bingguo, Zhuang Zhitao, Gan Yu, and Chen Fengdong
The ratio between the intensity of focused spot and the total intensity of the fiber output, which is spot focusing efficiency, affects the sampling signal to noise ratio of single-fiber digital scanning based on liquid crystal spatial light modulator (SLM). Using sequence coordinate ascend algorithm to control the inpThe ratio between the intensity of focused spot and the total intensity of the fiber output, which is spot focusing efficiency, affects the sampling signal to noise ratio of single-fiber digital scanning based on liquid crystal spatial light modulator (SLM). Using sequence coordinate ascend algorithm to control the input field, the light emitted from the multimode fiber can be focused. The theoretical and experimental results show that the sum of normalized objective function and spot focusing efficiency is approximately constant. In order to improve spot focusing efficiency, the normalized objective function value must be minimized. The affect of the multimode fiber output light intensity on the convergence of the normalized objective function is analyzed. The numerical simulations and experiments show that the normalized objective function convergence rate changes slowly and spot focusing efficiency deteriorates with the output light intensity increasing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 705003 (2015)
Comparison of Impacts of Control Errors and Measurement Errors of Working Parameters on Accuracies of Point Cloud Products from Airborne LiDAR
Wang Jianjun, Li Xiaolu, Xu Tongle, Li Dongxing, and Huo Wenxiao
In airborne LiDAR, some working parameters have both control errors and measurement errors, such as attitude angles, flight trajectories, and scan angle of laser scanner. Both kinds of errors can deteriorate qualities of point cloud products. In order to find out compensation measures to improve accuracies of point cloIn airborne LiDAR, some working parameters have both control errors and measurement errors, such as attitude angles, flight trajectories, and scan angle of laser scanner. Both kinds of errors can deteriorate qualities of point cloud products. In order to find out compensation measures to improve accuracies of point cloud and the reconstructed digital surface model (DSM), impacts of the two kinds of errors are analyzed theoretically. Then, through numerical simulation, the working process of airborne LiDAR is simulated. The two kinds of errors of attitude angle parameters are taken as an example, and effects of attitude control errors and measurement errors on accuracies of point cloud products are quantitatively evaluated and compared. Simulation results show that, the qualities of point cloud products from airborne LiDAR depend on common impacts of the control errors and measurement errors. The control errors mainly cause varying of point density and distribution area of point cloud, resulting in decreasing of spatial sampling resolution of point cloud, the measurement errors mainly cause decreasing of positioning accuracy of point cloud. Both errors can add distortion to the reconstructed DSM. Therefore, it is necessary to take appropriate measures to compensate the impacts of the two kinds of errors, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 708003 (2015)
Numerical Simulation Research on Scattering Light Imaging of Surface Defects of Optical Components
Wang Shitong, Yang Yongying, Zhao Limin, Chai Huiting, Liu Dong, Bai Jian, and Shen Yibing
Strong diffraction and scattering effects can be caused by micro or sub-micro scaled surface defects of optical components. The distribution of scattering light on the image plane can not be explained simply by geometrical optical theories. The electromagnetic model of triangle-shaped and rectangular surface defects isStrong diffraction and scattering effects can be caused by micro or sub-micro scaled surface defects of optical components. The distribution of scattering light on the image plane can not be explained simply by geometrical optical theories. The electromagnetic model of triangle-shaped and rectangular surface defects is built by using finite difference time domain (FDTD) method. The distributions of scattering light in the near-field region and on the image plane are simulated. The scattering imaging experiment of sample defects is also performed. The sample defects are rectangular and fabricated by electron beam exposure and ion beam etching. The gray distributions in dark-field images are compared with intensity distribution of scattering light on the image plane and show a good consistency. The results provide significant theoretical references for defect calibration in optical manufacturing and testing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 708005 (2015)
A Method for Reducing the Error Accumulation in Sub-Aperture Stitching Interferometer for Flat Optics
Li Yong, Tang Feng, Lu Yunjun, Wang Xiangzhao, Guo Fudong, Li Jie, and Wu Feibin
The power of reference flat (RF) in interferometer is difficult to be calibrated accurately. It leads to stitching error accumulation effect in sub-aperture stitching interferometer for flat optics, and becomes the major restriction factor for improving stitching accuracy. A quantitative equation is deduced for calculaThe power of reference flat (RF) in interferometer is difficult to be calibrated accurately. It leads to stitching error accumulation effect in sub-aperture stitching interferometer for flat optics, and becomes the major restriction factor for improving stitching accuracy. A quantitative equation is deduced for calculating the power of RF from stitching accumulation error and stitching numbers. Then the power of RF is calibrated and removed in the process of stitching. The error Accumulation is reduced. A flat mirror with aperture of 450 mm×60 mm is tested by 8 sub- apertures. Compared with the test result of a large aperture interferometer, the stitching measurement error is reduced from λ/10 peak-valley value to λ/30 PV with power compensation. The stitching test accuracy is improved effectively. Using absolute flatness test, the high order surface figure of the RF is also calibrated. It is verified that the power is the main source of the error accumulation in stitching. Removing the high order surface figure of the RF cannot improve the stitching accuracy significantly..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 708006 (2015)
Calibration and Error Compensation of an Imaging Stokes Polarimeter Based on Rotating Quarter-Wave Plate Method
Zhang Xuebing, Li Yanqiu, Zheng Meng, and Li Jianhui
An imaging Stokes polarimeter based on rotating quarter-wave plate method is comprised of a rotating quarter-wave plate, a fixed polarizer, imaging optics and a photodetector. The fast-axis angle error and the retardation error of the quarter-wave plate are the main error sources of the imaging Stokes polarimeter basedAn imaging Stokes polarimeter based on rotating quarter-wave plate method is comprised of a rotating quarter-wave plate, a fixed polarizer, imaging optics and a photodetector. The fast-axis angle error and the retardation error of the quarter-wave plate are the main error sources of the imaging Stokes polarimeter based on rotating quarter-wave plate method. The measurement accuracy can be efficiently improved with the calibration and error compensation. For this purpose, the relations between the Stokes parameters of the incident polarized light and the two parameter errors of the quarter-wave plate are derived by investigating the rotating quarter-wave plate method and Fourier analysis method and therefore, a new calibration method is proposed. Horizontally polarized light is used as a standard reference light and measured to calculate the two parameter errors of the quarter-wave plate and then complete the error compensation by substituting them into the corresponding formula. The experimental results show that the average measurement accuracy is improved from 5.12% to 1.78%, which indicates that the proposed calibration and error compensation method is valid and effective..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 708007 (2015)
Measurement of Ultrashort Pulse Laser with Scanning Third Order Correlation Technique
Bao Wenxia, Zhang Nan, Kong Mengqing, and Zhu Xiaonong
Measurement results of femtosecond laser pulses with the home-made collinear and non-collinear, large dynamic range, scanning third-order correlation technique are analyzed theoretically and experimentally. It is found that the dynamic range is low for the collinear scanning third-order correlation method because of thMeasurement results of femtosecond laser pulses with the home-made collinear and non-collinear, large dynamic range, scanning third-order correlation technique are analyzed theoretically and experimentally. It is found that the dynamic range is low for the collinear scanning third-order correlation method because of the direct third harmonic generation of the fundamental light in air. While the non-collinear measurement does not have this problem and thus has a higher dynamic range, the non-collinear angle and spot size have a significant influence on the measured pulse duration. In particular, both theoretical simulation and experimental results show that the measured pulse duration increases with the beam angle and spot size in this latter case. Although both noncollinearand collinear approaches can help locate the weak satellite pulses, due to the artificial pulse broadening introduced in the non-collinear scheme, it will be difficult for using this method to resolve or distinguish the detailed structures around the main pulse or any closely located neighboring pulses..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 708009 (2015)
Lossless Binary Image Reconstruction in Diffractive Encryption System with Redundant Data
Wang Hongjuan, Wang Zhipeng, Hai Tao, Liu Xuyan, and Qin Yi
A method for image encryption by employing the diffraction imaging technique is proposed. Only a single diffraction intensity image is recorded without using interference equipment that makes the method much more efficient, and the transmision of the single ciphertext more convenient. Before encrypting, the redundant dA method for image encryption by employing the diffraction imaging technique is proposed. Only a single diffraction intensity image is recorded without using interference equipment that makes the method much more efficient, and the transmision of the single ciphertext more convenient. Before encrypting, the redundant data of the original binary image are extracted as the secret key, then the original binary image is encrypted by using optical diffraction image encryption method and the diffraction intensity image is the ciphertext. During image decryption, the redundant datas serve as partial input plane support constraint in phase retrieval algorithm iterative operation, which is employed for making algorithm convergences fastly. Computer simulation results verify the validity of the proposed approach. Its robustness against occlusion and noise attacks are also analyzed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 709002 (2015)
Generation and Propagation of Besinc-Correlated Partially Coherent Vortex Beams
Fang Guijuan, Lin Huichuan, and Pu Jixiong
The generation and propagation of a Besinc-correlated partially coherent vortex beam (BS-PCV beam) have been investigated. Based on the van Cittert–Zernike Principle, the spatial coherence distribution of the light beams, which radiated from the controllable annular extended incoherent light source is studied theoreticThe generation and propagation of a Besinc-correlated partially coherent vortex beam (BS-PCV beam) have been investigated. Based on the van Cittert–Zernike Principle, the spatial coherence distribution of the light beams, which radiated from the controllable annular extended incoherent light source is studied theoretically. The theoretical calculations show that, the spatial coherence of the light beams which radiate from controllable annular extended incoherent light source changes into partial coherence after propagation. Moreover, the spatial coherence of the light beams is Besinc-correlation. Experimentally, A BS-PCV beam with controllable spatial coherence is generated by using an annular extended incoherent light source and a spiral phase plate. Furthermore, by use of the double-slit interference the topology charge number is measured. Additionally, the propagation of BS-PCV beams in a free space is investigated based on extended Huygens-Fresnel Principle. The influence of the controllable spatial coherence on the propagation is investigated..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 713001 (2015)
Case Study of the Relationship between Aerosol Angstrom Exponent and Relative Humidity
Bo Guangyu, Xie Chenbo, Wang Bangxin, Wu Decheng, and Zhong Zhiqing
In order to determine the relative humidity (RH) impact on the aerosol Angstrom exponent (AE), a twowavelength lidar is employed to observe the aerosol AE, two typical case studies have been given at Hefei area based on the wind direction, one represents pollution aerosol case, and the other represents rural aerosol caIn order to determine the relative humidity (RH) impact on the aerosol Angstrom exponent (AE), a twowavelength lidar is employed to observe the aerosol AE, two typical case studies have been given at Hefei area based on the wind direction, one represents pollution aerosol case, and the other represents rural aerosol case. The result indicates that during the two cases the RH has a strong effect on the variety of the AE, but totally different correlation between the two parameters can be found. During the rural case, the RH is between 49.2%~91.9%, the AE is between 0.75~1.98, and the AE of the pollution case is between 0.2~1.56 when the RH changed between 58.7%~96.0% . The pollution case presents a negative correlation between the RH and the AE, due to the aerosol hydrophilic growth with a Junge distribution. It is noteworthy that the rural case presents a positive correlation between the RH and the AE, the cause of this phenomenon is probably that particle size distribution is multimodal distribution composed of fine particles and coarse particles of dust pollution..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 713002 (2015)
Optical System Design of Star Camera with High Precision Better than Second Level
Wu Yanxiong, Wu Hongbo, Zhang Jizhen, Wang Lingjie, Zhu Yang, and Zhang Xin
In order to achieve accurate positioning measurement, high precision star camera is the key equipment of the space mapping or reconnaissance camera. The difficulties of optical system design about star camera with long focal length are analysized. The new structure type of dual Gauss transited to telephoto is adopted, In order to achieve accurate positioning measurement, high precision star camera is the key equipment of the space mapping or reconnaissance camera. The difficulties of optical system design about star camera with long focal length are analysized. The new structure type of dual Gauss transited to telephoto is adopted, a subsecond star camera optical system is designed with focal length of 200 mm, relative aperture of F/2, angel of 7.5°×7.5°, spectrum range of 500~800 nm. Due to the characteristics of stellar temperature in large range, the color correction of optical system is realized without the use of special dispersion glass, the consistency of centroid position is achieved under different color temperatures of stellar. In order to compensate thermal drifting, negative temperature coefficient of refract index of the crown glass is adopted, by which sub- second precision of athermalization is come true. It is shown that, the distortion of the optical system is better than 0.003%, the lateral color aberration is less than 1.5 μm, the accuracy of centroid position is better than 0.2″ in the range of 2600 K~9800 K . Between 0 ℃ and 30 ℃, the change of focal length is less than 5.1 μm, the accuracy of centroid position is better than 0.4″, except the 1 field..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 716001 (2015)
Holography and Information Processing
A Method of Chromatic Aberration Compensation in Computer-Generated Holography Based on Digital Lens Area Sampling
Wang Dehong, Wang Cui, Li Fangzhuan, Wang Di, and Wang Qionghua
For the chromatic aberration problem caused by the uncoincidence of reconstructed image′s center in the procession of color optoelectronic reconstruction of computer-generated holography, a compensation method based on digital lens area sampling is proposed. By changing the sampling area of digital lens, the reconstrucFor the chromatic aberration problem caused by the uncoincidence of reconstructed image′s center in the procession of color optoelectronic reconstruction of computer-generated holography, a compensation method based on digital lens area sampling is proposed. By changing the sampling area of digital lens, the reconstructed image′s position can be changed. The offset distance of reconstructed image is reversely equal to the offset distance of the sampling area in horizontal and vertical directions. In the experiment, a single spatial light modulator within spatial- multiplexing method is used by setting the blue reconstructed image as standard and readjusting the positions of red and green reconstructed images, the chromatic aberration compensation can be achieved. The experiment verifies the feasibility of the proposed method..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 709001 (2015)
Nonlinear Image Encryption System Based on JTC and Its Removing Noise and Resisting Attack Properties Research
Shen Xueju, Liu Xumin, Cai Ning, Cai Jianjun, and Lu Jun
By analyzing the reason of big noise and low quality of decryption image in the joint transform correlation (JTC) encryption system, a kind of nonlinear JTC image encryption system is proposed. A new encryption image is obtained when JTC encryption image is divided by key power spectrum. On the one hand, new encryptionBy analyzing the reason of big noise and low quality of decryption image in the joint transform correlation (JTC) encryption system, a kind of nonlinear JTC image encryption system is proposed. A new encryption image is obtained when JTC encryption image is divided by key power spectrum. On the one hand, new encryption image can remove noise caused by amplitude non- uniformity of key Fourier spectrum and improve the quality of decryption image. Simulation results show that the correlation coefficient between new Lena decryption image and original image increases from 0.4104 to 0.7190 and root mean square (RMS) value decreases from 0.8154 to 0.7089, and that the correlation coefficient between new binary text decryption image and original image increases from 0.8458 to 0.9785 and RMS value decreases from 0.6887 to 0.4583. On the other hand, new encryption image can resist chiphertext only attack (COA) arithmetic attack. Simulation results show that using the COA arithmetic, high quality original image can be restored from JTC encryption image, but information of original image can not be obtained from new encryption image. This system improve the security of JTC encryption system effectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 709003 (2015)
Materials
Polymeric MZI Thermo-Optic Switch with Low Power Consumption
Sun Jingwen, Sun Jian, Wang Yanshuang, Qu Lucheng, Wang Xibin, Wang Fei, and Zhang Daming
A polymeric Mach- Zehnder interferometer (MZI) thermo- optic (TO) switch with low power consumption is designed and fabricated. The polymer materials have the advantages of low thermal conductivity and high thermo-optic coefficient. Therefore it can reduce the power consumption of the thermooptic device effectively. ThA polymeric Mach- Zehnder interferometer (MZI) thermo- optic (TO) switch with low power consumption is designed and fabricated. The polymer materials have the advantages of low thermal conductivity and high thermo-optic coefficient. Therefore it can reduce the power consumption of the thermooptic device effectively. The TO switch is designed on the SiO2 substrate with selecting the Norland optical adhesive (NOA73) as the core layer and using Poly (methyl methacrylate- glycidyl methacrylate) [P(MMAGMA)] as the upper cladding. The light field and thermal field distribution of the TO switch are both simulated. The TO switch is fabricated by using the traditional semiconductor technology. At 1550 nm wavelength, the extinction ratio of the device is 20.2 dB and the power consumption is only about 9.14 mW. The rise time and the fall time of the switch are 174 ms and 292 ms, respectively..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 706001 (2015)
Femtosecond Laser Fabricated Superhydrophobic Copper Surfaces and Their Anti-Icing Properties
Long Jiangyou, Wu Yingchao, Gong Dingwei, Fan Peixun, Jiang Dafa, Zhang Hongjun, and Zhong Minlin
In recent years, the anti-icing properties of superhydrophobic surfaces attract tremendous attention of researchers. However, the effect of surface microstructures and wettabilities on their anti-icing properties is still controversial. Different microstructures on copper surface are fabricated by a femtosecond laser. In recent years, the anti-icing properties of superhydrophobic surfaces attract tremendous attention of researchers. However, the effect of surface microstructures and wettabilities on their anti-icing properties is still controversial. Different microstructures on copper surface are fabricated by a femtosecond laser. After surface chemical modification, these surfaces show superhydrophobicity combined with different adhesion to water. Their anti-icing properties are studied. The result shows that all these superhydrophobic surfaces delay the ice formation in low temperatures (-5 ℃，-10 ℃). In addition, the superhydrophobic surface adhesion to water affects the antiicing property. Low superhydrophobic surface adhesion to water benefits their anti-icing property..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 706002 (2015)
Study on Ultrafast Laser Fabrication of UV-FIR Ultra-broad-band Antireflection Surface Micro-Nano Structures and Their Properties
Fan Peixun, Long Jiangyou, Jiang Dafa, Zhang Hongjun, and Zhong Minlin
Antireflection properties on material surfaces are of great value in many fields including solar utilization, sensing, stealth, aerospace technology, military, etc. Through the interaction of picosecond laser with metallic materials, unique micro/nano hierarchical structures are produced on Cu, Al, Ti, and H13 steel suAntireflection properties on material surfaces are of great value in many fields including solar utilization, sensing, stealth, aerospace technology, military, etc. Through the interaction of picosecond laser with metallic materials, unique micro/nano hierarchical structures are produced on Cu, Al, Ti, and H13 steel surfaces, realizing significant antireflection properties through the ultra-broad spectrum band from ultraviolet (UV) to infrared (FIR) region. Wherein the total reflectance of the micro/nano structured Al, Ti, and H13 steel surfaces in the UV-VIS-NIR region are reduced down to around 10%, 5%, and 5%, respectively. The average reflectance of the disordered porous structures covered by abundant nanoparticles on Cu surface in the UV-VIS, UV-NIR, UV-MIR, and UV-FIR regions are reduced down to around 3% , 6% , 9% , and 10% , respectively, exhibiting extraordinary ultra- broad- band antireflection property. The formation mechanisms of the ultra-broad-band antireflection property as well as its relationship with surface micro/nano structures are discussed..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 706003 (2015)
Efficient emission of 2.7 μm from Diode-pumped Er3+/Nd3+ Co-doped Bismuth Germanate Glass
Zhao Guoying, Fang Yongzheng, Zhang Na, Liu Yufeng, and Hu Lili
Mid-infrared emission spectroscopic property of Er3+/Nd3+ co-doped bismuth germanate glasses pumped by 808 nm excitation is discussed. The absorption transition parameters of Er3+ are estimated by Judd-Ofelt theory. For the luminescence of 2.7 mm, the as-made glasses is qualified with higher spontaneous transition probMid-infrared emission spectroscopic property of Er3+/Nd3+ co-doped bismuth germanate glasses pumped by 808 nm excitation is discussed. The absorption transition parameters of Er3+ are estimated by Judd-Ofelt theory. For the luminescence of 2.7 mm, the as-made glasses is qualified with higher spontaneous transition probability (58.46 s-1) and larger calculated emission cross section (8.34×10-21 cm2). The large energy transfer probability rate between Er3+ and Nd3+ indicate that the co-doping Nd3+ greatly enhances the 2.7 μm emission of Er3+, and this might indicate that this glass is potentially applicable materials for mid-infrared laser devices..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 706004 (2015)
Study on Damaging Characteristic of 10.6 μm CW Laser to Ge-Sb-Se Chalcogenide Glass
Wu Lihua, Dai Shixun, Zhang Peiqing, Liu Zijun, Wang Xunsi, Shen Xiang, Xu Tiefeng, and Nie Qiuhua
Damaging characteristic of continuous wave (CW) CO2 laser to Ge-Sb-Se chalcogenide glass is studied based on the thermal conduction and experimental study. Studies show that the laser induced damage is mostly damage when heat accumulation causing temperature rising exceeds decomposition temperature of glass. Damage chaDamaging characteristic of continuous wave (CW) CO2 laser to Ge-Sb-Se chalcogenide glass is studied based on the thermal conduction and experimental study. Studies show that the laser induced damage is mostly damage when heat accumulation causing temperature rising exceeds decomposition temperature of glass. Damage characteristics include meteorite pits, micro-cracks and holes. Se substance is vaporized because of its low melting points, accordingly glass is decomposed in irradiation area. For a Ge-Sb-Se glass of 3 mm thickness, its absorption coefficient is 0.013 cm-1, the sample may be induced damage by a laser irradiation of 74.3 kW/cm2, which is basically consistent with numerical analysis results..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 706005 (2015)
Influence of Porosity on Photothermal Radiometry of Carbon Fiber Reinforced polymers
Wu Enqi, Xu Zihong, Guo xinxin, and Andreas Mandelis
To study the influence of porosity on photothermal radiometry (PTR) signals of carbon fiber reinforced polymers (CFRPs), a four- layered PTR model is developed and PTR measurements are performed. Three laser beams with different diameters are used to measure 9 CFRP samples with varied porosity levels. The measured amplTo study the influence of porosity on photothermal radiometry (PTR) signals of carbon fiber reinforced polymers (CFRPs), a four- layered PTR model is developed and PTR measurements are performed. Three laser beams with different diameters are used to measure 9 CFRP samples with varied porosity levels. The measured amplitudes and phases of the PTR signals are normalized. The result shows that the phase of PTR signal increases with decreased beam size if the laser power are kept constant. For a beam size of 0.2 mm, the PTR phase increases when the CFRP sample porosity decreases..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 706006 (2015)
Measurement and Metrology
Enhanced Roll-Angle Measurement Interferomerter
Ju Aisong, Hou Wenmei, Yang Wei, Luo Jialin, and Ke Youlong
All guide kinematic pair of machine tools have three rotating degrees of freedom which include pitching angle, yaw angle and roll angle, in which the roll angle is mostly difficulty to measure for the producing reasons. The existing roll angle measurement interferometer is comprised of two symmetrical wedge prisms and All guide kinematic pair of machine tools have three rotating degrees of freedom which include pitching angle, yaw angle and roll angle, in which the roll angle is mostly difficulty to measure for the producing reasons. The existing roll angle measurement interferometer is comprised of two symmetrical wedge prisms and two symmetrical wedge mirrors. A enhanced roll angle measurement interferometer which only uses one wedge prism and one wedge mirror is proposed. The proposed system uses less optical component and has implemented the same measurement resolution, which is more stability. The two beams with different frequencies are paralleled which is efficient for reducing the dead path errors and eliminating the cross talk of other freedom errors. By using the phase meter of which the resolution is 2π/512, the roll angle resolution of this system is 2 μrad..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 708001 (2015)
Thermal Effect Analysis of 1560 nm Laser Frequency Doubling in a PPLN Crystal
Zhang Yuantao, Qu Qiuzhi, Qian Jun, Ren Wei, Xiang Jingfeng, Lü Desheng, and Liu Liang
Based on the frequency doubling mechanism of a continuous wave 1560 nm laser single-passing a PPLN crystal, the dependence of nonlinear conversion efficiency on temperature is investigated. The effects of thermal expansion of the crystal′s polarization period on the nonlinear conversion efficiency and matching temperatBased on the frequency doubling mechanism of a continuous wave 1560 nm laser single-passing a PPLN crystal, the dependence of nonlinear conversion efficiency on temperature is investigated. The effects of thermal expansion of the crystal′s polarization period on the nonlinear conversion efficiency and matching temperature have been studied in detail. By using finite element method, the temperature fields in the whole crystal and on the output facet are numerically calculated, and the nonlinear conversion efficiency is extracted when the laser passes through the crystal. The dependences of the crystal size, input laser power, and the strategy of heat dissipation on the temperature field are also presented, respectively. It is demonstrated that the performance of the PPLN crystal on frequency doubling can be improved by a wider crystal and the materials with good heat conductivity surrounding the crystal..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 708002 (2015)
Study and Application on Transparent Plate Thickness Measurement Based on Laser Triangulation with Light Compensation
Yang Guishuan, Chen Tao, and Zhang Zhifeng
A novel transparent plate thickness measurement method based on laser triangulation with the light compensation is put forward, and a design of transparent plate thickness measuring device is based on single laser displacement sensor, which is applied to correct the focal plane in excimer laser micromachining of transpA novel transparent plate thickness measurement method based on laser triangulation with the light compensation is put forward, and a design of transparent plate thickness measuring device is based on single laser displacement sensor, which is applied to correct the focal plane in excimer laser micromachining of transparent material based on projection lithography. Firstly, the relationship between bending light and transparent plate location based on laser triangulation method is built, and the relationship between displacement of scattering light spot and plate thickness is analyzed. The changing rules of measuring results caused by the distance between transparent plate and scattering base plate and the position change of scattering base plate are also analyzed. Then transparent plate thickness measuring device based on single laser displacement sensor is designed. The relationship between spot migration and transparent plate thickness is tested, and compensation coefficient of polymethyl methacrylate (PMMA) thickness measured by experiments is 0.441. Based on the theoretical analysis and experimental verification, the results show that laser displacement sensor readings are linear relation with the thickness of transparent plate, and the distance between transparent plate and scattering surface has no effect on it. The average absolute error of PMMA plate thickness measurement is less than 0.01mm, and the average relative error is 0.6%, which can meet the precision requirements for processing biochip of PMMA base by the excimer laser (KrF, 248 nm) micromachining system..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 708004 (2015)
Measure the Complex Amplitude of Laser Mode by Mach-Zehnder Point Diffraction Interferometer
Dong Zheliang, Feng Guoying, Hu Lili, and Zhang Shulin
Mach-Zehnder point diffraction interferometer is used to reconstruct the complex amplitude by obtaining the information of phase and intensity of laser mode from a interferogram. A method to reconstruct the complex amplitude by using point-diffraction interferometry based on fast Fourier transform is analyzed theoreticMach-Zehnder point diffraction interferometer is used to reconstruct the complex amplitude by obtaining the information of phase and intensity of laser mode from a interferogram. A method to reconstruct the complex amplitude by using point-diffraction interferometry based on fast Fourier transform is analyzed theoretically. The phase and intensity distributions are deduced when laser mode propagates in the free space. The simulation of phase and intensity distributions with the experimental results are compared. The results show that complex amplitude can be restored by point-diffraction interferometry..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 708008 (2015)
Spectroscopy
Study on Oxygen Velocity Measurement in Wind Tunnel by Wavelength Modulation - TDLAS Technology
Jia Liangquan, Liu Wenqing, Kan Ruifeng, Liu Jianguo, Yao Lu, Xu Zhenyu, Dai Yunhai, and Wei Min
In order to effectively measure gas flow rate in wind tunnel, based on the principle of laser Doppler frequency shift, combined with wavelength modulation tunable diode laser absorption spectroscopy (TDLAS) technology, using HITRAN database, oxygen (O2) molecular absorption spectral line near 13144.5 cm-1 is selected aIn order to effectively measure gas flow rate in wind tunnel, based on the principle of laser Doppler frequency shift, combined with wavelength modulation tunable diode laser absorption spectroscopy (TDLAS) technology, using HITRAN database, oxygen (O2) molecular absorption spectral line near 13144.5 cm-1 is selected as the research object. A gas flow measurement model is built in the software, the flow velocity measurement results are simulated and analyzed. Supersonic wind tunnel devices are used in the laboratory to set up a set of wavelength modulation flow measurement system based on TDLAS technology. Through the experiment, second harmonic signal of O2 is extracted. According to the second harmonic of O2 molecular absorption spectral line frequency shift, the flow velocity in the wind tunnel is reversed. The experimental results show that, in the laboratory environment, velocity measured by the system reaches 707.6 m/s. The experimental results are consistent with the supersonic wind tunnel design, and the measurement error is 5.47% . The results prepare for the research of system miniaturization, which measures flow rate based on wavelength modulation - TDLAS, and flight experiments..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 715001 (2015)
Thin Films
Size Effects of Photoelectric Signal Receiver on Weak Absorption Measurement for Optical Coatings
Fu Yanyan, Li Dawei, Liu Xiaofeng, Zhao Yuanan, Guo Meng, and Zhang Lei
Based on the weak absorption measurement system with surface thermal lens (STL) technique, different power pump laser is used to irradiate the sample and record the intensity distribution of probe beam with beam quality analyzer. Making the pixel coordinates of the strongest intensity point of the probe beam as the cenBased on the weak absorption measurement system with surface thermal lens (STL) technique, different power pump laser is used to irradiate the sample and record the intensity distribution of probe beam with beam quality analyzer. Making the pixel coordinates of the strongest intensity point of the probe beam as the center, by taking multiple pixel from both sides of the center, different sizes of photoelectric signal receiver can be represented and photo- thermal signal intensity which obtained by different sizes of photoelectric signal receiver can be analyzed. The photo-thermal signal as a function of size of photoelectric signal receiver is experimental measured. The experimental results show that with the size of photoelectric signal receiver increasing, the coverage area of detection exceeds the probe beam peak area，and then the photo-thermal signal deviates from linearity gradually, which enlarges the measurement error. Therefore, to improve the accuracy of measurements，the actual size of photoelectric signal receiver should be minimized on the premise of guaranteeing measurement limit..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 42, Issue 7, 707001 (2015)
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