Journals >Chinese Journal of Lasers
Contents
2010
Volume: 37 Issue 10
48 Article(s)
Export citation format
Research Article
Study of Uniform Pumping and Uniform Cooling on Thin Disk Laser
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Uniform pumping and uniform cooling are key techniques to reduce thermo-optical distortion and to achieve high beam quality output for solid-state laser. Uniform pumping and uniform cooling technique researches about bonding thin disk are carried out. Pumping uniformity of 95% is achieved by using lens compress and wavUniform pumping and uniform cooling are key techniques to reduce thermo-optical distortion and to achieve high beam quality output for solid-state laser. Uniform pumping and uniform cooling technique researches about bonding thin disk are carried out. Pumping uniformity of 95% is achieved by using lens compress and waveguide uniform pumping coupling frame. The temperature distribution uniformity is better than 96% through optimizing cooling channels. The experimental results show that the wave-front distortion of thin disk has been controlled effectively. The mean square root (RMS) of reflect wave-front distortion is about 0.35 μm ignoring the defocusing effect when the pumping intensity is 230 W/cm2..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2437 (2010)
A Laser Diode-Pumped Nd∶YVO4 Crystal Micro-Chip Green Laser with High Polarization Ratio
Lin Haifeng, Chen Jianlin, and Xiong Feibing
A laser diode (LD)-pumped high polarization state intracavity frequency doubling all-solid green laser is reported. By using two optical axis orthogonal Nd∶YVO4 crystals to act as laser gain medium, eliminating the depolarization effect of single Nd∶YVO4 crystal, the high polarization green laser is obtained. And with A laser diode (LD)-pumped high polarization state intracavity frequency doubling all-solid green laser is reported. By using two optical axis orthogonal Nd∶YVO4 crystals to act as laser gain medium, eliminating the depolarization effect of single Nd∶YVO4 crystal, the high polarization green laser is obtained. And with optical contact between each crystal, the micro-chip green laser is realized. With the injection pump power of 1.8 W, 336 mW TEM00 green laser at 532 nm is achieved, the light-light conversion efficiency is up to 18.7%, and the polarization rate is 110∶1. This laser has the advantages of being simple and easily attainable at a low cost, and it is suitable for batch production..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2441 (2010)
Thermal Effects and Thermal Focal Length Measurement of Laser Diode End-Pumped Solid-State Lasers
Pan Sunqiang, Liu Chong, Zhao Zhigang, Dong Yantao, Xiang Fangli, Ge Jianhong, Xiang Zhen, and Chen Jun
Thermal effects of laser diode (LD) end-pumped solid-state laser are important factors, which affect the laser output characteristics and the system performance. The accurate thermal focal length measurement is an important prerequisite for resonator design. The temperature gradient distribution of LD end-pumped solid-Thermal effects of laser diode (LD) end-pumped solid-state laser are important factors, which affect the laser output characteristics and the system performance. The accurate thermal focal length measurement is an important prerequisite for resonator design. The temperature gradient distribution of LD end-pumped solid-state laser is calculated with the heat conduction equation. The phase difference and the Fraunhofer diffraction pattern of the probe laser are obtained. Based on the above theoretical model, a new method by means of Fraunhofer diffraction pattern of probe laser to determine the thermal focal length is presented, which enables real-time on-line measurement. The optical path difference is calculated from the Fraunhofer diffraction pattern of probe laser, and then the thermal focal length is calculated from the optical path difference. The thermal focal length of laser crystal is measured experimentally, and the feasibility of the method is proved by comparing with the experimental values measured by unstable cavity method..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2445 (2010)
Radially or Azimuthally Polarized Laser Based on Mode Selection of Thermally Induced Bifocus
Yu Yi, Pang Yu, Sun Yinhong, Wang Weimin, and Gao Qingsong
Side-pumped NdYAG rods have different radial and azimuthal thermal focal lengths. Radial and azimuthal thermal focal length are measured with rotary slit and polarized He-Ne laser. A laser oscillator is designed to produce low-loss stable oscillation in a single polarization. At the pumped power of 440 W, radially polaSide-pumped NdYAG rods have different radial and azimuthal thermal focal lengths. Radial and azimuthal thermal focal length are measured with rotary slit and polarized He-Ne laser. A laser oscillator is designed to produce low-loss stable oscillation in a single polarization. At the pumped power of 440 W, radially polarized beam at 31.7 W with M2=2.5 is achieved. And at the pumped power of 470 W, azimuthally polarized beam at 30.2 W with M2=2.8 is achieved. The results show that radially or azimuthally polarized beam with higher power can be achieved with mode selection of thermally induced bifocus, but the laser is sensitive to pumped power..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2451 (2010)
Study of Electro-Optic Q-Switched Nd∶YVO4 Laser with a Wedge Angle
Zhang Yunshen, Chen Meng, Pang Qingsheng, Chang Liang, and Li Gang
A design to realize electro-optic Q-switch in Nd∶YVO4 laser without polarizer is presented, in which a Nd∶YVO4 crystal with a wedge angle is used by analyzing the polarization of natural birefringent crystal. This design has the advantages of simplifying cavity components, shortening cavity length, and reducing cavity A design to realize electro-optic Q-switch in Nd∶YVO4 laser without polarizer is presented, in which a Nd∶YVO4 crystal with a wedge angle is used by analyzing the polarization of natural birefringent crystal. This design has the advantages of simplifying cavity components, shortening cavity length, and reducing cavity loss, and can obtain higher power and narrower pulse width. Voltage-decreased Q-switching is realized by using a La3Ga5SiO14 crystal and a Nd∶YVO4 crystal with the size of 3 mm×3 mm×5 mm, 10° wedge angle. 2.2 W average power, 6.3 ns pulse width, optical-to-optical efficiency of 39.2%, and more than 300 kW peak power are obtained when the repetition rate is 1 kHz..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2456 (2010)
Analysis of Nonlinear Dynamic Behaviors for the Twin-Stripe Laser
Zhang Yali, Zhang Xuliang, and Zhu Weijie
The twin-stripe laser is an important type of monolithic lasers. Based on the rate equations, the nonlinear dynamic behaviors for the twin-stripe laser are analyzed by the numerical method. The transient responses are elaborately discussed for the twin-stripe laser with two kinds of different guidance mechanisms, and iThe twin-stripe laser is an important type of monolithic lasers. Based on the rate equations, the nonlinear dynamic behaviors for the twin-stripe laser are analyzed by the numerical method. The transient responses are elaborately discussed for the twin-stripe laser with two kinds of different guidance mechanisms, and initial phase difference under different bias configurations. It is concluded that the instability/chaos is the intrinsic operation of the twin-stripe laser. Either phase-locked operation without detuning or stable output with two-wavelength only can be obtained under certain running conditions besides the special structure design..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2460 (2010)
Investigation of the TEM00-Mode Output Character from LD Side-Pumped Two Nd:YAG Rods in Laser Resonator
Dong Yantao, Zhao Zhigang, Pan Sunqiang, Liu Chong, Mao Qianmin, Xiang Zhen, and Chen Jun
In high power polarized TEM00-mode laser diode(LD) side-pumped NdYAG laser resonator, thermal birefringence is the main factor influencing the output power of the polarized TEM00-mode. By using the construction of two NdYAG rods in laser resonator, depolarization effects caused by thermal birefringence have been compenIn high power polarized TEM00-mode laser diode(LD) side-pumped NdYAG laser resonator, thermal birefringence is the main factor influencing the output power of the polarized TEM00-mode. By using the construction of two NdYAG rods in laser resonator, depolarization effects caused by thermal birefringence have been compensated effectively. After analyzing the influences of the resonator parameters on the laser output performance and optimizing the laser resonator, 35 W polarized TEM00-mode output power is obtained..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2467 (2010)
Design and Numerical Simulation for Unstable Ring Resonator with 90°Beam Rotation Employed in Ceramic YAG Disk Laser
Yang Meixia, Zhong Ming, Xia Huijun, and Liu Wenbing
A design of unstable ring resonator with 90°(UR90) beam rotation employed in ceramic YAG disk laser is presented .The system of beam rotation is built up by a prism and two thin ceramic YAG disks which are placed vertically. Fast Fourier transform method(FFT) is used to simulate the mode of UR90 beam rotation. TheA design of unstable ring resonator with 90°(UR90) beam rotation employed in ceramic YAG disk laser is presented .The system of beam rotation is built up by a prism and two thin ceramic YAG disks which are placed vertically. Fast Fourier transform method(FFT) is used to simulate the mode of UR90 beam rotation. The effect of inhomogeneous gain on laser mode of an UR90 beam rotation is also analyzed. For two laser-diode side-pumped disk laser, the difference between the mode of UR90 and normal unstable resonator is compared. It provides evidences that UR90 beam rotation adopted by solid-state laser is feasible..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2472 (2010)
4.5 W All-Fiber Narrow-Linewidth Two-Tone Fiber Laser Based on Stimulated Brillouin Scattering
Chen Hongwei, Wang Xiaolin, Yang Chunbo, Zhou Pu, Leng Jinyong, Chen Shengping, and Hou Jing
A 4.5 W all-fiber narrow-linewidth two-tone laser based on stimulated Brillouin scattering is established. The wavelength separation of two-tone laser is 0.06 nm. The output power is 4.5 W and the optical conversion efficiency is 50%. Spectral properties, output power properties and coherence of the laser are compared A 4.5 W all-fiber narrow-linewidth two-tone laser based on stimulated Brillouin scattering is established. The wavelength separation of two-tone laser is 0.06 nm. The output power is 4.5 W and the optical conversion efficiency is 50%. Spectral properties, output power properties and coherence of the laser are compared with single-tone fiber laser experimently. Experiment results indicate that the narrow-linewidth two-tone fiber laser has the similar output power properties with the single-tone fiber laser. The visibility of the far-field interference pattern reaches 80%, when the two-tone fiber laser is at the max output power. The narrow-linewidth two-tone fiber laser can be used for coherent beam combination..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2477 (2010)
Multiwavelength Brillouin/Erbium Fiber Source with 40 nm Tuning Range
Zhao Junfa, Yang Xiufeng, Liu Zhuolin, Tong Zhengrong, Liu Yange, and Zhao Qida
A widely tunable multiwavelength Brillouin/erbium fiber source is experimentally demonstrated. The Brillouin Stokes signals return back to the linear cavity owing to the effect of stimulated Brillouin scattering. The influence of the self-lasing modes is effectively eliminated because of the weak reflectivity. The tuniA widely tunable multiwavelength Brillouin/erbium fiber source is experimentally demonstrated. The Brillouin Stokes signals return back to the linear cavity owing to the effect of stimulated Brillouin scattering. The influence of the self-lasing modes is effectively eliminated because of the weak reflectivity. The tuning range of the fiber source is only limited by the bandwidth of erbium-doped fiber amplifier and the tuning range of Brillouin pump signal. The pump threshold of Brillouin gain is effectively reduced by the double-pass Brillouin pump signal amplification. The fiber source provides a tuning range of 40 nm (1530～1570 nm). At the Brillouin pump power of 2 mW and the 1480 nm pump power of 110 mW, 5 output channels with 0.084 nm channel spacing from 1540 to 1566 nm are achieved..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2482 (2010)
Lock-in Effect in Fiber Ring Laser Gyros
Su Jue, and Qian Jingren
Taking account of the backscattering in a ring cavity, resonance behavior of two counter-propagating lasing beams is analyzed and the dynamic lasing frequencies as a function of rotation rates are obtained in a close form. The condition for occurring lock-in effect in the gyro is also obtained easily from the vector diTaking account of the backscattering in a ring cavity, resonance behavior of two counter-propagating lasing beams is analyzed and the dynamic lasing frequencies as a function of rotation rates are obtained in a close form. The condition for occurring lock-in effect in the gyro is also obtained easily from the vector diagrams. It is noted that the Rayleigh backscattering is the main source to form the lock-in effect, although the scattering is weak in a fiber at infrared wavelength, which can be considerably enhanced in an active resonator. The above mentioned analytic close form of dynamic frequencies is confirmed by a fiber ring laser gyro experiment, and the gyro is locked-in when its rotation rate is less than 10° /s..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2487 (2010)
Influence of Temperature Distribution on Stimulated Brillouin Scattering in High Power Single-Frequency Fiber Amplifiers
Leng Jinyong, Liu Chi, Guo Shaofeng, Qi Yunfeng, Xu Xiaojun, and Zhao Yijun
The influences of temperature distribution on stimulated Brillouin scattering (SBS) in high power single-frequency fiber amplifier are studied, based on the rate equations combining with SBS. The results indicate that temperature gradients along a fiber can broaden the SBS gain profile and thereby suppress SBS. The thrThe influences of temperature distribution on stimulated Brillouin scattering (SBS) in high power single-frequency fiber amplifier are studied, based on the rate equations combining with SBS. The results indicate that temperature gradients along a fiber can broaden the SBS gain profile and thereby suppress SBS. The threshold of pump power and the output power of amplifier can be increased significantly by cooling fibers around the output port of amplifier actively. The length and location of fibers cooled to suppress SBS have the optima, which are influenced by pump power, temperature distribution and length of total fiber in amplifier. The threshold of pump power and output power of amplifier can be increased more than 2 times under the optimum condition..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2491 (2010)
Thermal Characteristic of High Beam Quality Laser Diode Array
Wang Zhiqun, Yao Shun, Cui Bifeng, Wang Zhiyong, and Shen Guangdi
Aiming at the development trend of high-power semiconductor devices and multiple short laser diode array components integrated structure applied to a single all-fiber structure optical fiber lasers and lack of related heat control theory, the finite element software ANSYS is used to simulate the thermal properties of aAiming at the development trend of high-power semiconductor devices and multiple short laser diode array components integrated structure applied to a single all-fiber structure optical fiber lasers and lack of related heat control theory, the finite element software ANSYS is used to simulate the thermal properties of a high beam quality laser diode arrays based on the standard heat conduction heat sink structure. By changing the spacing and the number of light-emitting unit of the light-emitting elements in the array, the traditional structure of high fill factor cm-bar array is transitioned to short- or multi-unit integrated device thermal model. A theoretical basis is provided for the design and high-performance, long life heat of this new high beam quality device by its hot characteristics..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2497 (2010)
Influence of Fine Structure Mixing Rate on Laser Diode Pumped Alkali Laser
Yang Zining, Wang Hongyan, Lu Qisheng, Li Yuandong, and Xu Xiaojun
Influence of the fine structure mixing rate on the CW end laser diode pumped alkali laser (DPAL) is studied based on the rate equation theory, result shows that the relaxation of the P1/2 and P3/2 energy levels should be described by the upward and downward fine structure mixing rates rather than the thermal equilibriuInfluence of the fine structure mixing rate on the CW end laser diode pumped alkali laser (DPAL) is studied based on the rate equation theory, result shows that the relaxation of the P1/2 and P3/2 energy levels should be described by the upward and downward fine structure mixing rates rather than the thermal equilibrium hypothesis. The influence of fine structure mixing rate on laser threshold can be neglected when it is very large comparing to the spontaneous emission and electronic quenching rates. Not only the match of the pump and atomic absorption width but also sufficient fine structure mixing rate to avoid the absorption saturation is needed for the effective absorption of the pump power. The laser medium length and the temperature can be optimized to achieve high optical-optical efficiency even at low fine structure mixing rate..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2502 (2010)
Effect of Cylinder Disturbed Flow on Heat Transfer Performance of Mini-Channel Radiators
Liu Dong, Liu Minghou, and Wang Yaqing
With water as working fluid, the heat transfer performance of different height/width ratio mini-channel radiators with circular cylinder disturbed flow in front of the mini-channels was experimentally studied. It is found that the 4 mm in height mini-channel radiators with circular cylinder disturbed flow can achieve hWith water as working fluid, the heat transfer performance of different height/width ratio mini-channel radiators with circular cylinder disturbed flow in front of the mini-channels was experimentally studied. It is found that the 4 mm in height mini-channel radiators with circular cylinder disturbed flow can achieve heat dissipation of 3.2×106 W/m2 when surface temperature is 81.7 ℃ and flow rate is 58.2 L/h. The influence of circular cylinder disturbed flow on heat dispersion is unnoticeable when the flow rate is low. However, as the flow rate increasing, it is becoming distinct. The channel with circular cylinder disturbed flow has the best height when the flow rate is fixed, and the effect of circular cylinder disturbed flow is related to flow rate for the same channels. A general empirical formula is proposed to evaluate cooling performance of the radiators with consideration of Nusselt number as a faction of thermal entrance region length, disturbed flow diameter/ length ratio and height/width ratio. This empirical formula can express the heat transfer of similar radiators well..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2508 (2010)
Study on Characteristics of Vertical-Cavity Surface-Emitting Laser by Laser Spectrometry
Chen Jiehua, Du Runchang, Zhao Jicheng, Ma Hong, and Gu Sihong
An experimental scheme is proposed and realized, with which the characteristic of a vertical-cavity surface-emitting laser(VCSEL), a key component of a passive coherent population trapping(CPT) atomic clock, is studied through atomic absorption spectra toward laser. By switching on and off the input microwave for modulAn experimental scheme is proposed and realized, with which the characteristic of a vertical-cavity surface-emitting laser(VCSEL), a key component of a passive coherent population trapping(CPT) atomic clock, is studied through atomic absorption spectra toward laser. By switching on and off the input microwave for modulating VCSEL, atomic absorption spectra toward monochromatic and multi-chromatic laser are alternatively recorded. The characteristics of VCSEL, including temperature response rate, temperature change along microwave power, wavelength response to its temperature, and the CPT state preparing efficiency are studied with the spectra measurement. This scheme provides a convenient experimental method to measure and study VCSEL, and a useful tool for developing CPT atomic clocks..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2515 (2010)
Effects of Imaging System Noise on the Correction Capability of Adaptive Optics without a Wavefront Sensor
Yang Huizhen, and Li Xinyang
The atmosphere turbulence and imaging system noise can degrade and distort the imaging of the extended object. Adaptive optics technology is usually used to mitigate the wave-front aberrations caused by the atmosphere turbulence. An adaptive optics (AO) system with stochastic parallel gradient descent (SPGD) algorithm The atmosphere turbulence and imaging system noise can degrade and distort the imaging of the extended object. Adaptive optics technology is usually used to mitigate the wave-front aberrations caused by the atmosphere turbulence. An adaptive optics (AO) system with stochastic parallel gradient descent (SPGD) algorithm and a 61-element deformable mirror is simulated to restore the image of a turbulence-degraded extended object and the gray level variance function is used as the optimized object by controlling algorithm. Based on the above simulation mode, effects of imaging system noise on the correction capability of adaptive optics are discussed. The results show that the correct capability is not affected when the signal noise ratio (SNR) is bigger than 20 dB for relative small turbulence, while the correction capability becomes worse obviously as the SNR decreases. Under the same SNR, the stronger the turbulence, the bigger the effect on the correction capability..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2520 (2010)
Optical Properties of Aerosol in Planetary Boundary Layer Measured by Raman Lidar at Hefei in Summer and Autumn
Bo Guangyu, Xie Chenbo, Liu Dong, Chen Tao, Wang Bangxin, Wang Zhenzhu, Zhong Zhiqing, and Zhou Jun
A Raman-Mie lidar (RML) has been developed for measuring the extinction coefficient, backscattering coefficient and lidar ratio of atmospheric aerosols. Planetary boundary layer (PBL) aerosols were investigated with the lidar system during summer and autumn, 2009 at Hefei area. Result shows that during the experiment, A Raman-Mie lidar (RML) has been developed for measuring the extinction coefficient, backscattering coefficient and lidar ratio of atmospheric aerosols. Planetary boundary layer (PBL) aerosols were investigated with the lidar system during summer and autumn, 2009 at Hefei area. Result shows that during the experiment, remarkable variety dose no exist in the vertical profiles of lidar ratio, which means vertical distribution of aerosols in the PBL has a uniform mixture state and the same microphysical properties. Average value of lidar ratio is 64.4±6.1 sr in summer, which is a little higher than that in autumn with a value of 51.5±5.1 sr, this difference may caused by the change of particle component in the PBL,or the meteorologic factor. Lidar ratio does not change too much in the same season, especially in autumn. During the experiment, lidar ratio accumulated from 43 to 72 sr, with a mean value of 57.9 sr, which means particles in the PBL at Hefei area could be polluted continental aerosols..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2526 (2010)
Synchronization of Chaotic Lasers in Unidirectional Chain-Connection Network
Lü Ling, Li Gang, Meng Le, Yang Ming, Guo Li, Zou Jiarui, Li Chunqing, and Chai Yuan
A method of realizing synchronization of chaotic lasers in unidirectional chain-connection network is proposed. The single-mode laser Lorenz-Haken system with chaotic characteristics is taken as node to construct the complex network in unidirectional chain-connection. The appropriate Lyapunov function is constructed, aA method of realizing synchronization of chaotic lasers in unidirectional chain-connection network is proposed. The single-mode laser Lorenz-Haken system with chaotic characteristics is taken as node to construct the complex network in unidirectional chain-connection. The appropriate Lyapunov function is constructed, and the structure of control input and the conditions of realizing global synchronization of the network are discussed and confirmed based on Lyapunov stability theory. It is found that the entire network is steady when the control signal is input only one node of the network. Then the correctness of theoretical analysis is verified by the artificial simulation..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2533 (2010)
Study of Fabrication and Application of Hollow-Core Photonic Crystal Fiber Based In-Line Fiber-Optic Etalon
Duan Dewen, Rao Yunjiang, Zhu Tao, and Fan Yan′en
Hollow-core photonic crystal fiber (HCPCF) based in-line fiber-optic etalon (ILFE), due to its high sensitivity to strain and low thermal coefficient, can be made with longer cavity length compared with traditional ILFE, making it suitable in quasi-distributed multipoint stain detection systems. The ways of enhancing tHollow-core photonic crystal fiber (HCPCF) based in-line fiber-optic etalon (ILFE), due to its high sensitivity to strain and low thermal coefficient, can be made with longer cavity length compared with traditional ILFE, making it suitable in quasi-distributed multipoint stain detection systems. The ways of enhancing the output signal of HCPCF based multiplexing strain detecting systems are analyzed. The effect of temporal coherence length of light source is analyzed through examples. A spatial-frequency division multiplexing (SFDM)/coarse-wavelength division multiplexing (CWDM) of ILFE strain sensors with four HCPCF-based ILFE strain sensors is demonstrated. The experimental results show that a strain accuracy of ±5 με can be achieved. Such an HCPCF-based ILFE strain sensor multiplexing system could be used for large engineering structure health monitoring..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2554 (2010)
Mode Transmission Characteristics in Hollow-Core Bragg Fibers with Slowly Variation in Outer Diameter
Shi Lichao, Zhang Wei, Xing Wenxin, Li Zhiguang, Wang Wentao, Huang Yidong, and Peng Jiangde
During the fabrication process of hollow-core Bragg fibers, outer diameter variations would be induced unavoidably, which lead to band gap shifts of the one dimensional photonic crystal structures in the fiber claddings, impacting their transmission characteristics severely. The mode transmission characteristics of holDuring the fabrication process of hollow-core Bragg fibers, outer diameter variations would be induced unavoidably, which lead to band gap shifts of the one dimensional photonic crystal structures in the fiber claddings, impacting their transmission characteristics severely. The mode transmission characteristics of hollow-core Bragg fibers with slowly sine variation in outer diameter have been investigated. The simulation results show that, despite the transmission characteristics are different between different mode classes and the mode losses are different between modes in the same mode class with different orders, the diameter variation tolerances are almost the same. In the case calculated, the diameter variation tolerances of the TE0n mode are about 9%, and 6%～7% for the TM0n, HE and EH modes. The method deployed can be used for any diameter variations and structure parameters..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2559 (2010)
Spectral Characteristics of Bragg Fiber Grating Based on Fused Taper Fiber
Jiang Weiwei, Zhao Ruifeng, Wei Yan, and Jian Shuisheng
Taper fiber is a kind of fiber with variational diameter along the longitudinal direction.The couple mode equations of fiber Bragg grating (FBG) based on fused taper fiber are solved by numerical method of broyden and shooting,and the effect of taper along the longitudinal direction on spectrum of FBG is analysed.The rTaper fiber is a kind of fiber with variational diameter along the longitudinal direction.The couple mode equations of fiber Bragg grating (FBG) based on fused taper fiber are solved by numerical method of broyden and shooting,and the effect of taper along the longitudinal direction on spectrum of FBG is analysed.The results show that the spectrum of FBG shifts to short wavelength and the bandwidth broadens because of the effect of taper compared with the condition of uniform FBG. The peak reflectivity and the transmission reduce because the ability of restricting optical power of the fiber core becomes weak.The phenomena become more obvious as the taper becomes bigger.Taper fibers are fabricated by fused taper method,and different taper fibers are obtained through changing the motor velocity on the basis of the same fused taper length. The relation between motor velocity and the loss of the taper fiber is analysed. A Bragg grating is written in taper fiber with 248 nm ultraviolet laser and uniform phase mask of 537 nm,then the effect of different tapers on the spectrum is analysed. The experimental results are consistent with the theoretical results..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2565 (2010)
Spectral Tunability of Magneto-Optic Fiber Grating-Based Fabry-Perot Structures
Lu Xin, and Wu Baojian
The transmission characteristics of magneto-optic fiber Bragg grating(MFBG)-based Fabry-Perot(FP) structures dependent on the magneto-optical effect and the initial phase of effective refractive index distribution of gratings are analyzed by the transfer matrix method. By adjusting the applied magnetic field, the functThe transmission characteristics of magneto-optic fiber Bragg grating(MFBG)-based Fabry-Perot(FP) structures dependent on the magneto-optical effect and the initial phase of effective refractive index distribution of gratings are analyzed by the transfer matrix method. By adjusting the applied magnetic field, the function of tunable filtering for MFBG-FP structures is implemented and the magnetic control of transmission peaks is also useful for eliminating the influence of the initial index phase difference. For the case of high reflectivity of gratings, the position and wavelength spacing of transmission peaks can be analytically expressed by the effective cavity length and the effective magneto-optic coupling coefficient. The magnetic tunability of MFBG-FP is enhanced with the increase of the ratio of FP cavity to MFBG magneto-optic coupling coefficients. When the ratio is more than 1, the MFBG-FP has an advantage over the corresponding MFBG in magnetic tuning..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2570 (2010)
Beam Transmission
Studies on Interference Characteristics of Cat-Eye Effect Reflected Light of Defocused Optical Lens
Zhao Yanzhong, Sun Huayan, Zhao Linfeng, and Huang Chenggong
Based on the idea that the cat-eye effect reflected light of defocused optical lens can be regarded as a spherical wave, and by using Collins formula and the method of expanding the aperture function into a finite sum of complex Gaussian functions, the distribution formula of the cat-eye effect reflected light interferBased on the idea that the cat-eye effect reflected light of defocused optical lens can be regarded as a spherical wave, and by using Collins formula and the method of expanding the aperture function into a finite sum of complex Gaussian functions, the distribution formula of the cat-eye effect reflected light interfered with the reference incident light is deduced. Through numerical computation, laws governing the variation of the distribution and stripe series of the interference field with the focal shift are obtained. Then an experiment is done to validate the laws. The results show that off-focus of the optical lens is a necessary condition for the cat-eye effect reflected light to be interfered with the incident light and stripes are brought, the interference cirque gradually moves inside and the stripe number becomes larger with the increasing of the focal shift, and the relation between the interference stripe number and the focal shift can be correctly described by the geometric optical path function on nearby condition..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2537 (2010)
Refractive Optical Reshaper that Converts a Laser Gaussian Beam to a Flat-Top Beam
Shang Jianli, Zhu Xiao, Chen Peng, Zhu Guangzhi, Wang Wei, Ren Songqing, and Yan Qiong
In order to convert a laser Gaussian beam to a collimated flat-top beam, a new reshaper with only one aspheric lens is designed based on double aspheric lenses reshaper. In the theoretical model, a more accurate calculation method of curves function of aspheric lens is given. The reshaping effection, brought by the chaIn order to convert a laser Gaussian beam to a collimated flat-top beam, a new reshaper with only one aspheric lens is designed based on double aspheric lenses reshaper. In the theoretical model, a more accurate calculation method of curves function of aspheric lens is given. The reshaping effection, brought by the change from the parameter of system and laser beam, is given through numerical analysis and optical design software simulation. It is illustrated that the flatten degree of the laser beam can be improved apparently using this new kind of reshaper. The novel method avoids some shortcomings of traditional refractive optical reshaper such as large volume, complexity of regulating, etc, and enhances the reliability and practicability of device..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2543 (2010)
Self-Focusing Effect of Ultra-Short Laser Pulse Propagation During Quasi-Phase Matched Crystal
Zhang Shuanggen, Huang Zhangchao, Xue Yuming, Lü Fuyun, and Yao Jianghong
The physical model of ultra-short laser pulse propagation during quasi-phase matched crystal is built and modified nonlinear Schrdinger equation is solved with step Fourier method. The temporal and spatial characteristics of femto-second laser pulse propagation in periodically poled lithium niobate (PPLN) crystal are The physical model of ultra-short laser pulse propagation during quasi-phase matched crystal is built and modified nonlinear Schrdinger equation is solved with step Fourier method. The temporal and spatial characteristics of femto-second laser pulse propagation in periodically poled lithium niobate (PPLN) crystal are achieved numerically. It is found that when the fundamental power is beyond the critical power, temporal splitting and spatial focusing of pulse are induced by self-focusing effect. Temporal splitting results in pulse width decrease with the increment of propagation distance, and minimal width is obtained at the focal point. On the other hand, spatial focusing brings decrement of focused diameter with the increment of propagation distance, and minimal diameter is obtained at the focal point and then diffused outward. Finally, the peak intensity of the pulse reaches maximal value at the focal point, and then reduces gradually. The length of quasi-phase matched crystal is restricted by self-focusing effect during ultra-short laser frequency doubling process..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2550 (2010)
Laser Manufacturing
Effect of Standoff Distance on Flow Field of Assist Gas in Cutting Slot in Laser Cutting
Dang Dongxian, Sheng Xiaojun, Hu Jun, and Luo Jingwen
Adopting two typical assemble nozzles which called taper nozzles and convergence nozzles as targets, the three-dimensional and plane symmetrical impinging jet model of laser cutting comprised workpieces is established and the flow field of assist gas is computed by adopting the integral form of N-S equation and RNG k-εAdopting two typical assemble nozzles which called taper nozzles and convergence nozzles as targets, the three-dimensional and plane symmetrical impinging jet model of laser cutting comprised workpieces is established and the flow field of assist gas is computed by adopting the integral form of N-S equation and RNG k-ε onflow model. The flow structure of assist gas and study the influence of standoff distance on flow field in cutting slot are calculated. The investigation reveals that the dynamics in cutting slot of convergence nozzle is more predominant than that in taper nozzle and at least two reasonable cutting scopes exist to make the assisting gas in cutting slot have predominant dynamic characteristic. In the end, laser cutting experiment and analysis are shown..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2625 (2010)
Parameters Analysis of Residual Stress Induced by Laser Shock Processing
Wu Xianqian, Huang Chenguang, and Song Hongwei
The paper focuses on the influencing parameters to the plastically affected depth and maximum residual stress in the metallic target after laser shock processing. Firstly, the dimensional analysis method is employed to find the controlling parameters, and the relationships of plastically affected depth, maximum residuaThe paper focuses on the influencing parameters to the plastically affected depth and maximum residual stress in the metallic target after laser shock processing. Firstly, the dimensional analysis method is employed to find the controlling parameters, and the relationships of plastically affected depth, maximum residual stress versus peak pressure, pressure duration and laser spot size are given. Secondly, a two-dimensional axisymmetric finite element model based on LS-DYNA package is built, and the dynamic responses of metallic target subject to laser shock processing are computed with different input parameters. The result shows that the plastically affected depth is proportional to pressure duration, and the maximum residual stress is independent with it, but both of them are not affected by laser spot size within a certain range,while they have approximate linear relationship with peak pressure after reaching to a certain level..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2632 (2010)
Influence of Micro-Fluctuation of Laser Power to Processing Quality
Zhong Rutao, Qin Yingxiong, and Tang Xiahui
Utilizing transverse flow CO2 laser, the influence of micro-fluctuation of laser power to processing quality is studied under high speed laser processing. The relationship between processing quality and processing velocity is analyzed, and evaluation of laser beam quality is discussed. The result indicates that the fluUtilizing transverse flow CO2 laser, the influence of micro-fluctuation of laser power to processing quality is studied under high speed laser processing. The relationship between processing quality and processing velocity is analyzed, and evaluation of laser beam quality is discussed. The result indicates that the fluctuation frequency of voltage/current of high power transverse-flow CO2 laser is 300 Hz when stimulated by direct current power supply, which resulted in laser power fluctuation of 300 Hz. The influence of the fluctuation to processing quality can be ignored under lower speed processing, but the fluctuation will affect processing quality under high speed processing. Aiming at the processing of high quality and high speed, the evaluation standard of time-beam-quality should be brought up..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2638 (2010)
Influence of Immersion Medium Surroundings on Laser Heat Processing on Substrate Surface
Yi Peng, Liu Yancong, Shi Yongjun, Lun Guande, and Ren Hongwei
Under the consideration of the nonlinearity of the material thermal parameters and heat convective transfer coefficient, a validated three-dimensional numeric modal of laser heat dynamic process was established with base body immersed in the medium surroundings such as air, pure water and 2# martempering oil using air Under the consideration of the nonlinearity of the material thermal parameters and heat convective transfer coefficient, a validated three-dimensional numeric modal of laser heat dynamic process was established with base body immersed in the medium surroundings such as air, pure water and 2# martempering oil using air stream for protecting the melten pool, the field of temperature and residual stress of thermal response within different natural cooling media were studied comparatively. The results showed that, the law of the temperature field is essentially consistent with three kinds of surroundings, and the substrate highest temperature appeared in the air. The surface high and low temperature region were effected obviously by oil-cooling and water-cooled respectively; the remelting and heat-affected depth could be controlled effectively by oil-cooled, while larger temperature gradient and cooling rate would be gained within water. Residual stress distribution was affected significantly by medium surroundings. Internal stress of substrate was too large with air-cooled and there was stress concentration at both ends and the tensile stress was main. While substrate thermal stress had been released timely in water and oil surroundings, and water-cooled environment was more effective in reducing the residual stress..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2642 (2010)
Experiments of Laser Cutting of Aluminum Alloy Sheet Based on Vaporization-Melt Ratio Controlled Method
Wang Xuyue, Meng Qingxuan, Kang Renke, Xu Wenji, Guo Dongming, and Wang Lianji
To improve the laser cut quality of slot array antenna sheet, a new method of laser precision cutting is presented based on vaporization-melt ratio controlled method. The cutting qualities of 6063 aluminum sheets of 0.5 mm in thickness are researched which are cut on a NdYAG pulse laser cutting system, and the effects To improve the laser cut quality of slot array antenna sheet, a new method of laser precision cutting is presented based on vaporization-melt ratio controlled method. The cutting qualities of 6063 aluminum sheets of 0.5 mm in thickness are researched which are cut on a NdYAG pulse laser cutting system, and the effects of vaporization-melt ratio on kerf width, recast layer, kerf sides, and adhering slag are studied as well. Observation on samples of different vaporization-melt ratios (2.62, 3.06, 4.11) shows that high vaporization-melt ratio can improve laser cut quality with decreasing recast layer and increasing the smooth zone of kerf sides. The cut kerfs of 0.2 mm in width on the top, no adhering slag on the bottom, recast layer of 2.03 μm in thickness, and percentage of the smooth zone 40% out of whole thickness are obtained by experiment. The research on vaporization-melt ratio provides the deeper understanding of mechanism of laser cutting, and improves laser cut quality effectively..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2648 (2010)
Microstructure of In-Site Synthesis TiC Hardened Coating by Laser Irradiation
Xu Ning, Zhang Qunli, and Yao Jianhua
Featured with excellent physical and chemical properties, TiC has important significance and practical application value. A new method to synthesis TiC by combining laser and sol-gel technology is reported. TiO2 sol-gel coating is prepared on the surface of 45# steel and then treated by NdYAG laser. The microstructure Featured with excellent physical and chemical properties, TiC has important significance and practical application value. A new method to synthesis TiC by combining laser and sol-gel technology is reported. TiO2 sol-gel coating is prepared on the surface of 45# steel and then treated by NdYAG laser. The microstructure and performance of the coating after laser treating are tested by scanning electronic microscope (SEM), X-ray diffraction (XRD), and micro-hardness tester respectively. The results show that the surface of coating is flat, and there is a metallurgical bonding between hardened coating and parent metal. The coating is consisted of Fe, TiC, and FeTiO3，and the particle of TiC with size of 1～3 μm distributes on the topside of the coating. With dispersion reinforced phase TiC, the hardness of the hardened coating increases obviously. The average micro-hardness reaches 950 HV0.1, which is 3 times more than that of substrate..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2653 (2010)
Impact of Aluminizing on Effects of K417 Material by Laser Shock Processing
[in Chinese], [in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
Fatigue resistance on cast nickel-base superalloy K417 by laser shock processing(LSP) can be enhanced. Aluminizing is necessary in order to improve the oxidation resistance and fuel gas corrosion resistance. The impact of aluminizing on the LSP effects of K417 material is researched. According to the changes of residuaFatigue resistance on cast nickel-base superalloy K417 by laser shock processing(LSP) can be enhanced. Aluminizing is necessary in order to improve the oxidation resistance and fuel gas corrosion resistance. The impact of aluminizing on the LSP effects of K417 material is researched. According to the changes of residual stress in 900 ℃, although some of the residual compressive stress caused by LSP will be released, the experimental results show that the fatigue resistance of the sample by LSP is 285.5 MPa while that of the sample by alumetizing after LSP is 339.5 MPa. It is indicated that the LSP and the aluminizing can be used in the same process..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2658 (2010)
Micro-Structural Enhancement Mechanism of LY2 Aluminum Alloy by Means of a Single Laser Shock Processing
Lu Jinzhong, Luo Kaiyu, Feng Aixin, Zhong Junwei, Sun Guifang, Zhang Lei, and Qian Xiaoming
The effects of laser shock processing (LSP) on grain size, element content and microstructure are investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM) observations in the top surface, the sever plastic deformation layer, the minor plastic deformation layer and the substrate afteThe effects of laser shock processing (LSP) on grain size, element content and microstructure are investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM) observations in the top surface, the sever plastic deformation layer, the minor plastic deformation layer and the substrate after a single laser shock processing. The influences of LSP on micro-structure and grain size of LY2 aluminum alloy are discussed, and the enhancement mechanism of a single LSP on LY2 aluminum alloy is also addressed. After a single LSP impact, the change of dislocation structure can be also clearly seen at different layers, i.e., it varies from dislocation lines (DLs) to dislocation tangles (DTs) and dense dislocation walls (DDWs), to subgrains or refined grains as functions of the distance from the top surface. It is found that the microstructure is obviously refined due to the ultra-high plastic strain induced by multiple LSP impacts..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2662 (2010)
Characteristics Comparison of Laser-TIG Arc Interaction Using High Power CO2 and Yb:YAG Laser
Wu Shikai, Xiao Rongshi, Yang Wuxiong, and Chen Kai
The characteristics of both laser beam and TIG arc are investigated during the interaction between the vertical incident laser and TIG arc by using a laser power meter, a beam quality diagnosis instrument and a high speed camera. The experimental results demonstrate that, when CO2 laser beam passes through TIG arc, theThe characteristics of both laser beam and TIG arc are investigated during the interaction between the vertical incident laser and TIG arc by using a laser power meter, a beam quality diagnosis instrument and a high speed camera. The experimental results demonstrate that, when CO2 laser beam passes through TIG arc, the laser power is attenuated dramatically, the beam is defocuses and even a laser supported combustion wave is generated. In this case, the beam quality is seriously worsened. On the other hand, the arc voltage is dropped and the arc column is expanded. However, the beam power, beam diameter, arc voltage and arc column seldom change during TIG arc interacted with YbYAG laser. Under the experimental conditions, the inverse bremasstrahlung absorption coefficient calculated is 14.14～26.29 m-1 for CO2 laser, 1.1～2.03 m-1 for YAG laser and the refractive index is 0.99249～0.99454 for CO2 laser, 0.99992～0.99994 for YAG laser, respectively. The inverse bremsstrahlung absorption coefficient for YAG laser is two orders of magnitude lower than that for CO2 laser. Meanwhile, there is less difference between the refractive index of YAG laser-TIG and YAG laser-air, so there is no obvious refraction of the TIG arc to the YAG laser, which is the main reason for the great difference between the CO2 laser-TIG and YAG laser-TIG interaction..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2667 (2010)
Studies of the Effects and Mechanism of Electromagnetic Stirring on the Microstructures and Hardness of Laser Cladding WC-Co Based Alloy Coating
Yu Benhai, Hu Xuehui, Wu Yu′e, and Yang Dongsheng
Effects of electromagnetic stirring on the microstructures of the laser cladding WC-CO based layers are studied. Both experimental and theoretical analysis indicate that the microstructures of the laser cladding layers under electromagnetic stirring are much finer and more uniform than those without electromagnetic stiEffects of electromagnetic stirring on the microstructures of the laser cladding WC-CO based layers are studied. Both experimental and theoretical analysis indicate that the microstructures of the laser cladding layers under electromagnetic stirring are much finer and more uniform than those without electromagnetic stirring. High qualitative layers which are free of porosity and cracks are obtained from the laser cladding with electromagnetic stirring. The influences of different electromagnetic stirring strengths on the hardness of the laser cladding layers are also investigated. The results show that the hardness increases correspondly with the increase of the electromagnetic stirring strength..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2672 (2010)
Experimental Study of Pulse Laser Processing Fracture Notch of Main Bearing Cap of Crankcase Bearing Bracket
Kou Shuqing, Wang Jinwei, Yang Shenhua, Yang Hongyu, and Zhong Zhaopeng
The fracture splitting notch is processed by NdYAG pulse laser on the material of engine crankcase bearing bracket. The result shows that, the organization of laser heat-affected zone is refined, the melting zone produces the dendritic primary crystal and the ledeburite, the transformation hardening zone obtains hiddenThe fracture splitting notch is processed by NdYAG pulse laser on the material of engine crankcase bearing bracket. The result shows that, the organization of laser heat-affected zone is refined, the melting zone produces the dendritic primary crystal and the ledeburite, the transformation hardening zone obtains hidden needle martensite and the retained austenite. The analysis of X-ray diffraction (XRD) indicates that the carbon density of the melting area is bigger than that of the transformation hardening zone. The micro hardness of the region nearby the fracture splitting notch is higher than that of the parent metal, the hardened effect is obvious and the micro hardness of the melting zone is approximately 260 HV higher than that of the transformation hardening zone. The hardening layer of the fracture splitting notch increases as the pulse power and the pulse width of laser increase, and reduces as the laser scanning speed increases. The depth of the hardening layer is between 0.232～0.625 mm. The fracture splitting notch that is processed by laser is the straight gap, which is a significant effect on the initiation fracture and fracture splitting of the gray iron. The influence law that laser power, pulse width, processing speed and other parameters on the morphology of fracture splitting notch is concluded, and the proposal to technological parameter′s choice is put forward..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2678 (2010)
Microstructure and Mechanical Properties of Laser Direct Deposited γ-TiAl Alloy
Zhang Yongzhong, Huang Can, Wu Fuyao, and Liu Liming
Thin wall samples from γ-TiAl(Ti-47Al-2Cr-2Nb-0.5W-0.15B)alloy are prepared on substrate of TC4 titanium alloy by laser direct deposition of coaxially fed metallic powders. The cracking behavior, microstructure, phase constitution, and mechanical properties of the deposited materials are investigated. The results indicThin wall samples from γ-TiAl(Ti-47Al-2Cr-2Nb-0.5W-0.15B)alloy are prepared on substrate of TC4 titanium alloy by laser direct deposition of coaxially fed metallic powders. The cracking behavior, microstructure, phase constitution, and mechanical properties of the deposited materials are investigated. The results indicate that the deposited γ-TiAl alloy presents high tendency for cracking. Decreasing the deposited wall length or introducing ductile titanium alloy as transition materials will mitigate the temperature gradient and thermal stress during deposition, thus avoid cracking. Laser direct deposited γ-TiAl alloy are full dense, composed of α2+γ lamellar colony and small amount of γ single phase. The size of the lamellar colony is about 10 μm. For as-deposited γ-TiAl alloy, the room-temperature tensile strengths are 810 MPa and 575 MPa along the longitude and build-up direction respectively, and the tensile strength under 750 ℃ along the build-up direction is 550 MPa and under 850 ℃ along longitude direction is 625 MPa..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2684 (2010)
Materials and Thin Films
Optical Limiting of Triphenylamine-Based Chromophores Containing Dibenzothiophene
Wang Xiaomei, Luo Jianfang, Wang Xiaohong, and Tao Xutang
Materials with large two-photon absorption (TPA) cross sections have the potential applications such as optical power limiting. Herein, the optical limiting of a series of multibranched chromophores based on triphenylamine is reported, and the comparative study of their two-photon absorption property pumped by 800 nm nMaterials with large two-photon absorption (TPA) cross sections have the potential applications such as optical power limiting. Herein, the optical limiting of a series of multibranched chromophores based on triphenylamine is reported, and the comparative study of their two-photon absorption property pumped by 800 nm nanosecond and femtosecond laser pulses, associative with the fluorescence lifetime on the one-photon excitation, is performed. Results show that, with higher generation, multibranched molecules possess longer excited lifetime and stronger re-absorption on the excited state. Thus, the effective two-photon absorption cross-section pumped by nanosecond laser pulse is larger. As a result, larger optical limiting efficiency is obtained..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2599 (2010)
Scattering Loss of a New Fluid State Laser Material
Gui Luo, Hou Chaoqi, Peng Bo, Fan Dianyuan, and Wei Wei
The scattering loss of a new mixed fluid state laser material varying with refractive index and temperature is studied experimentally. A platform of laser amplifier is established, on which the laser performance of the new material is shown by a comparison between the fluid state laser material and Nd-glass solid laserThe scattering loss of a new mixed fluid state laser material varying with refractive index and temperature is studied experimentally. A platform of laser amplifier is established, on which the laser performance of the new material is shown by a comparison between the fluid state laser material and Nd-glass solid laser material. Experimental results show that the fluid state laser material possesses typical laser gain, but its scattering loss is sensitive to the variation of refractive index and temperature. The scattering loss can be controlled under 0.0047 cm－1 with accurate refractive index matching. The results above indicate that the method of refractive index matching is able to ensure an acceptable scattering loss of this new type of fluid state laser material, so this new material has a potential ability in high power laser systems..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2605 (2010)
Near-Infrared Emission of Bi-Doped CdWO4 Crystals Grown by Bridgman Method
Yu Can, Xia Haiping, Luo Caixiang, Hu Yuan, Chen Hongbing, and Xu Jun
The CdWO4 crystals with good quality in the size of 25 mm×100 mm, doped Bi2O3 in 0.5 % molar fraction in the raw composition were grown by the bridgman method. The lower part of crystal which was grown at the initial stage appears yellow-green color, while the upper part of crystal blood-red color at final stage.The CdWO4 crystals with good quality in the size of 25 mm×100 mm, doped Bi2O3 in 0.5 % molar fraction in the raw composition were grown by the bridgman method. The lower part of crystal which was grown at the initial stage appears yellow-green color, while the upper part of crystal blood-red color at final stage. The absorption spectra were recorded. The emission spectra of various parts of crystal were investigated when excited by 808 nm and 980 nm. The weak emission band at 1396～1550 nm (centered at 1504 nm) and strong band at 1037～1274 nm(centered at 1078 nm)were observed, and their lifetime were 238 μs and 294 μs, respectively. The emission intensity at 1504 nm increased as the growth direction, while the intensity at 1078 nm reduced as the growth direction.The mechanism for the band emission were discussed from the obtained spectra. The emission band at 1078 nm was probable related to Bi ion, while the weak band at 1504 nm was probable related to the defects of the crystal..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2610 (2010)
Experimentation of Deposition Rate Control of SiO2 by E-Beam Auto-Sweeping
Wang Ning, Wei Chaoyang, Shao Jianda, Fan Zhengxiu, and Yi Kui
Deposition rate is one of the important technical parameters of producing optical thin film by e-beam. Deposition rate affects the microstructure and chemical composition of film, which affects the optical and mechanical properties of film greatly. SiO2 material is one of the important low refractive index materials foDeposition rate is one of the important technical parameters of producing optical thin film by e-beam. Deposition rate affects the microstructure and chemical composition of film, which affects the optical and mechanical properties of film greatly. SiO2 material is one of the important low refractive index materials for producing optical film. Because SiO2 has a low thermal conductivity and sublimes when evaporated, some pits may emerge on the surface of material during evaporation. The pits may affect the evaporation characteristics of SiO2, which is disadvantaged to the stability of deposition rate. Considering the special evaporation characteristics of SiO2, the experiment of deposition rate control of SiO2 by e-beam auto-sweeping is performed. The experiment uses the designed sweeping controller to control the evaporation spot moves on the surface of material through a designed sweeping path automatically. During sweeping, the deposition control is performed by the PID closed-loop control. The result of experiment shows that good surface characteristics of material and stable deposition rate..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2615 (2010)
Transient Optical Response of Bi20Sb80 Films Induced by Picosecond Laser Pulse
Zhai Fengxiao, Li Simian, Huang Huan, Jiang Laixin, Wang Yang, Lai Tianshu, and Wu Yiqun
A pump-probe system is employed to observe transient reflectivity change process of Bi20Sb80(BiSb) films induced by picosecond laser pulses. Spectroscopic ellipsometry and atomic force microscopy are used to study the micro-area optical properties and surface structures of irradiated areas. Experimental results indicatA pump-probe system is employed to observe transient reflectivity change process of Bi20Sb80(BiSb) films induced by picosecond laser pulses. Spectroscopic ellipsometry and atomic force microscopy are used to study the micro-area optical properties and surface structures of irradiated areas. Experimental results indicate that fast and recoverable switching can be achieved on BiSb films induced by single-shot or repeated picosecond laser pulses with a proper pumping fluence. The switching time is about 19 ns, which is independent on the laser fluences. The BiSb film is shown to be very promising for ultrafast super-resolution mask layer. These results are helpful for developing new mask layer materials with fast optical response and understanding the working mechanism of BiSb super-resolution mask layers..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2620 (2010)
Measurement and Metrology
Three-Dimensional Reconstruction Method Using Single CCD Based on Geometric Constraint of Bilateral Symmetry
Hu Chunhai, and Liu Bin
A new method of three-dimensional(3D) reconstruction using single CCD is proposed. A flat mirror with regular octagonal markers and a single CCD camera are used in the method. Bilaterally symmetrical structure is obtained by utilizing the object in space and its image in the flat mirror based on geometry of bilateral sA new method of three-dimensional(3D) reconstruction using single CCD is proposed. A flat mirror with regular octagonal markers and a single CCD camera are used in the method. Bilaterally symmetrical structure is obtained by utilizing the object in space and its image in the flat mirror based on geometry of bilateral symmetry. A single perspective image of this structure is equivalent to two perspective views of half of the structure. The two halves are projective equivalent in difference of a reflection transformation and the structure is auto-epipolar in the image taken by the camera. Flat mirror is not only a symmetrical plane, but also used as calibration plane. Extrinsic parameters of the camera are calculated by using vanishing point constraint of regular octagonal markers. The validity of the proposed method is proved experimentally and the results of 3D reconstruction are given. The advantages and limitations of this method are summarized. The designed regular octagonal sparse marker is possessed by orthogonality and parallelism at the same time. It is a new solution for online calibration of camera extrinsic parameters..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2576 (2010)
Optical Circuit Integrated Method of Single-Frequency Polarization Laser Interferometer for Nanometer Measurement
Liu Binbin, Li Liyan, Yang Jun, and Yuan Libo
A kind of orthogonal polarized laser interferometer (OPLI) optical components position fixed and performance detection methods are proposed which can be used for optical circuit integrated of sub-nanometer precision interferometer and its capability detection. OPLI integration technique and its performance on on-line dA kind of orthogonal polarized laser interferometer (OPLI) optical components position fixed and performance detection methods are proposed which can be used for optical circuit integrated of sub-nanometer precision interferometer and its capability detection. OPLI integration technique and its performance on on-line detective and evaluation method are built. Based on polarization intensity detection method, on-line optical detective and its evaluation system are constructed, and four channels polarized interference stripe quality and orthogonal polarized interference Lissajous trajectory′s ellipse parameter are detected, then nanometer precision interferometer optical component integration is realized. Experiment on stability and micro-vibration measurement is carried out to compare integrated and distributed OPLI performance. The experiment results indicated that the integrated OPLI is more stable than distributed OPLI and its signal to noise ratio (SNR) is 10 dB higher than distributed OPLI, its accuracy reached 10 pm/Hz at micro-vibration measurement experiment..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2582 (2010)
Thermal Diffusivities of Engineering Plastics Studied by the Revised Photoacoustic Piezoelectric Technique
Wan Dan, Gao Chunming, Sun Qiming, Lu Xu, and Zhao Binxing
The thermal diffusivities of engineering plastics had been studied by the revised photoacoustic piezoelectric (PAPE) technique. Firstly, the revised PAPE method was proposed and the corresponding experimental system was set up. The experimental system was calibrated and tested by investigating the diffusivity of pure aThe thermal diffusivities of engineering plastics had been studied by the revised photoacoustic piezoelectric (PAPE) technique. Firstly, the revised PAPE method was proposed and the corresponding experimental system was set up. The experimental system was calibrated and tested by investigating the diffusivity of pure aluminum and polytetrafluoroethylene(PTFE). The thermal diffusivities of eight kinds of engineering plastics were measured by the revised PAPE method. The results showed that engineering plastics have excellent insulation properties and the diffusivities are under 0.4 mm2/s. The theoretical and experimental results showed that the revised PAPE method can be used to accurately measure the thermal diffusivity of engineering plastics..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2588 (2010)
Computation and Analysis of Light Scattering by Monodisperse Biological Aerosols
Feng Chunxia, Huang Lihua, Zhou Guangchao, Han Jie, Zeng Aijun, Zhao Yongkai, and Huang Huijie
The T-matrix method is used numerically to calculate the light scattering patterns of monodisperse, randomly oriented, non-spherical biological aerosol particles based on prolate spheroidal and spherical models in order to obtain size and shape sensitive information. The shape dependence of the phase function for the bThe T-matrix method is used numerically to calculate the light scattering patterns of monodisperse, randomly oriented, non-spherical biological aerosol particles based on prolate spheroidal and spherical models in order to obtain size and shape sensitive information. The shape dependence of the phase function for the biological aerosol particles is discussed. The angular distributions of light scattered by Staphylococcus, Yersinia pestis, Francisella tularensis, Shigella dysenteriae and Burkholderia pseudomallei are presented and the size and shape dependence of the scattering matrix elements are illustrated in detail. At the forward- and side-scattering angles, the phase function has little dependence on particle shape for particles with equal extinction cross-section. It indicates that spherical model can be used to model non-spherical particles at these regions. The ratio of integrated backward- scattering at 170°～180°of F11(θ) to integrated forward-scattering at 0°～10° increases with the increases of the aspect ratio for non-spherical particles, which can be used to characterize particle shape. For aerosols of different sizes and shapes, the forward-scattering steepness ［F11(0°)-F11(5°)］/5 of F11(θ) increases with surface-equivalent radius, which provides theoretical basis for particle size detection. The ratio of integrated scattering at 170°～180°to integrated scattering at 0°～10°of F11(θ) as well as integrated scattering at 30°～90° of F22(θ)/F11(θ) increases with the aspect ratio, which can be used to determine the shape of particles. The study results in this paper provide a theoretical foundation to the design of particle size and shape analysis apparatus and the fast and effective detection of harmful biological micro-organisms in the air..
Chinese Journal of Lasers
- Publication Date: Mar. 30, 2020
- Vol. 37, Issue 10, 2592 (2010)
© Copyright 2018-2021 | Chinese Laser Press. All Rights Reserved 沪ICP备15018463号-20