Journals >Chinese Journal of Lasers
Contents
2008
Volume: 35 Issue 4
33 Article(s)
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Research Article
All-Fiber Q-Switched Ytterbium-Doped Double-Clad Laser
Ning Jiping, Zhang Weiyi, Shang Lianju, Fan Guofang, Han Qun, and Zhou Lei
Q-switched ytterbium-doped double-clad fiber laser has been studied in both theory and experiment, and theory model is built. A novel method based on 'the relationship between the energy utility ratio and the initial particle inversion' to solve the final particle inversion remaining is advanced . According to Q-switched ytterbium-doped double-clad fiber laser has been studied in both theory and experiment, and theory model is built. A novel method based on 'the relationship between the energy utility ratio and the initial particle inversion' to solve the final particle inversion remaining is advanced . According to the rate-equation theory of the Q-switched fiber laser, the general law that some important initial parameters, such as pump power, fiber core diameter, fiber length, output transmittance and fiber inherent loss influence the pulse width and energy is worked out. The analysis of these parameters is of important reference to designing the kindred Q-switched fiber lasers. In the experiment, a D-shape ytterbium-doped double clad gain fiber pumped by laser diode is used. A pigtailed acoustooptic Q-switch is inserted between the totally reflected fiber Bragg grating (FBG) and the combiner’s signal port. During the experiment, the operation of the acoustooptic Q-switched Yb3+-doped all-fiber laser is realized. The repetition rate can be adjusted continuously between 10 Hz and 100 kHz. The 3 μs pulse width and the 2.94 mJ pulse energy are obtained at the repetition rate of 500 Hz..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 483 (2008)
A Rubidium Laser Induced Dispersion Optical Filter at 775.9 nm
He Zhusong, Zhang Yundong, Liu Shuangqiang, Zhang Jing, and Yuan Ping
In order to improve the signal-to-noise ratios for free-space communication, remote sensing and lidar systems, a rubidium laser induced dispersion optical filter (LIDOF) at 775.9 nm was experimentally studied. Owing to unbalance of occupancy among in sublevels of the excited state, which is caused by selective excitatiIn order to improve the signal-to-noise ratios for free-space communication, remote sensing and lidar systems, a rubidium laser induced dispersion optical filter (LIDOF) at 775.9 nm was experimentally studied. Owing to unbalance of occupancy among in sublevels of the excited state, which is caused by selective excitation of a linearly polarized pump beam at 780 nm, dichroism and birefringence of the excited state are induced. So the polarization direction of 775.9 nm probe beam is rotated and transmitted. The filter has a peak transmission of 4% with a single bandwidth of 605 MHz. The peak transmission versus the cell temperature and pump intensity is also given..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 488 (2008)
Diffraction Effect of Liquid Crystal Spatial Light Modulator Using for Beam Deflection
Cai Dongmei, Yang Huizhen, Ling Ning, and Jiang Wenhan
A liquid-crystal spatial light modulator (LC-SLM) can be used to deflect laser beam, however its pixel structure and diffraction effect resulted from phase wrapping technique decreases its optical efficiency. The diffraction effect was analyzed theoretically and experimentally, and the relationship between fill factor A liquid-crystal spatial light modulator (LC-SLM) can be used to deflect laser beam, however its pixel structure and diffraction effect resulted from phase wrapping technique decreases its optical efficiency. The diffraction effect was analyzed theoretically and experimentally, and the relationship between fill factor and diffraction efficiency was demonstrated. 256 pixel×256 pixel liquid crystal spatial light modulator was used to alter the wavefront phase to achieve different deflections of a laser beam dynamically. The far field intensity distribution was measured at different deflection angles. The results show the diffraction efficiency decreases with the fill factor. Its measured diffraction efficiency was only 51.3% when the fill factor is 0.85. The phase wrapping technique make the LC-SLM form the structure asablazed grating and its diffraction efficiency decreases with the increase of the deflection angle..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 491 (2008)
Imaging by Single-Slit Streak Tube Laser Lidar
Wei Jingsong, Cheng Yuanli, Xu Qiang, He Manze, Liu Jinbo, Li Sining, and Wang Qi
A new type of three-dimensional (3D) imaging laser radar is introduced. It uses streak tube as the receiver, which makes the radar have the peculiarities of high frame rate and wide range angle. The principle of this method is introduced theoretically. The imaging ability of this method to far distant object was demonsA new type of three-dimensional (3D) imaging laser radar is introduced. It uses streak tube as the receiver, which makes the radar have the peculiarities of high frame rate and wide range angle. The principle of this method is introduced theoretically. The imaging ability of this method to far distant object was demonstrated experimentally. A laser imaging demonstration system was established. Some key parameters were measured, and some specially objective streak image of indoor and outdoor were accessed. The method was proved to be available..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 496 (2008)
Characteristics of High Power Volume-Bragg-Grating External Cavity Semiconductor Lasers
Bo Baoxue, Gao Xin, Qiao Zhongliang, Wang Yuxia, Lu Peng, Li Hui, Yao Yanping, Liu Chunling, Huang Bo, and Qu Yi
High wavelength shift coefficient varying with temperature and broad spectrum width are disadvantages of the output properties of high power broad-area semiconductor lasers. For improving the output spectral properties of broad-area semiconductor lasers, a volume-Bragg-grating (VBG) off-axis external cavity method was High wavelength shift coefficient varying with temperature and broad spectrum width are disadvantages of the output properties of high power broad-area semiconductor lasers. For improving the output spectral properties of broad-area semiconductor lasers, a volume-Bragg-grating (VBG) off-axis external cavity method was adopted with satisfied effect on spectrum and slope efficiency. The external cavity laser composes of a broad-area stripe semiconductor laser with fast-axis and slow axis beam collimation, and a VBG positioned off-axis. The broad-area stripe semiconductor laser has an emission width of 100 μm. High power output is achieved with 3.4 W at working current with 4.0 A. The slope efficiency is 1.0 W/A, and a narrower output spectrum of 0.2 nm width is realized compared with free output spectrum width of 2～3 nm. The wavelength shift coefficient varying with temperature is less than 0.015 nm/℃..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 501 (2008)
Theoretical Analysis and Experiment of “Smile” Correction for Diode Laser Bar
Deng Xinli, Liu Yun, Yin Honghe, Zhang Yan, Gu Yuanyuan, Feng Guangzhi, Shan Xiaonan, and Wang Lijun
Laser diode bar (LDB) curvature, namely “smile” produced in the manufacturing and packaging process, affects the application of LDB in laser diode pumped solid-state laser and external cavity laser diode array. Using plano-convex cylindrical lens, “smile” can be corrected to some extent. By geometrical optics approach Laser diode bar (LDB) curvature, namely “smile” produced in the manufacturing and packaging process, affects the application of LDB in laser diode pumped solid-state laser and external cavity laser diode array. Using plano-convex cylindrical lens, “smile” can be corrected to some extent. By geometrical optics approach and ORIGIN software, “smile” correction was simulated and coincided with the experiment. The results show that this method works best if the “smile” is a parabolic curvature, and the relative correction value can be as high as 90%. “Smile” is corrected obviously by using suitable lens with short-focal length. Moreover, error can be further reduced by amending focal length of lens..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 505 (2008)
Simulation and Analysis of 4H-SiC Metal-Semiconductor-Metal Ultraviolet Photodetector
Zhang Junqin, Yang Yintang, Lu Yan, Lou Lifei, and Zhao Yan
The I-V characteristics and spectral response of 4H-SiC metal-semiconductor-metal (MSM) ultraviolet (UV) photodetector have been simulated by MEDICI. The influence of the finger width and spacing of contact electrodes and epitaxial layer thickness on the spectral response has also been analyzed. The results show that tThe I-V characteristics and spectral response of 4H-SiC metal-semiconductor-metal (MSM) ultraviolet (UV) photodetector have been simulated by MEDICI. The influence of the finger width and spacing of contact electrodes and epitaxial layer thickness on the spectral response has also been analyzed. The results show that the density of dark current is about 10-13 A/μm and the photo-to-dark current ratio is at least 102 at different bias voltages. The range of spectral response is 200～400 nm and the peak responsivity lies in 347 nm. We have also found that the responsivity is increases with the increase of finger width or decrease of finger spacing. The epitaxial layer thickness has almost no effect on responsivity when wavelengh is less than peak wavelength, and the responsivity increases with the increase of epitaxial layer thickness when wavelengh is greater than peak wavelength..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 509 (2008)
Method and Simulation of Data Quality Control in Velocity Azimuth Display Inversion of Wind Lidar
Wang Chunhui, Li Yanchao, Xu Bo, and Li Shengfu
Since practical data information often contains small-amplitude wind speed and singularity point because of lots of disturbance such as earth-surface clutter, we put forward a method of pretreatment for quality control to data information before the velocity azimuth display (VAD) data inversion, which eliminates small-Since practical data information often contains small-amplitude wind speed and singularity point because of lots of disturbance such as earth-surface clutter, we put forward a method of pretreatment for quality control to data information before the velocity azimuth display (VAD) data inversion, which eliminates small-amplitude data and singularity point, then we proceed omnidirectional sampling and non-omnidirectional sampling inversion respectively. The precision of inversion is improved a lot, and the result of the simulation is consonant with reality. We simulate two kinds of linear wind field, that is, the linear wind field with the zero, first order harmonics and the zero, first, second order harmonics. We research into the omnidirectional sampling and non-omnidirectional sampling VAD methods by using the two kinds of wind field′s comparison. The result of this simulation indicates that the omnidirectional sampling VAD method has high performance in both two kinds of linear wind field′s inversion results, while the non-omnidirectional sampling VAD method has a very small effective sampling range in the linear wind fields without the second order harmonic, meanwhile, this method is affected by the second order harmonic partly..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 515 (2008)
Analysis of Properties of High Birefringence Photonic Crystal Fibers
Gong Taorong, Yan Fengping, Wang Lin, Li Yifang, Liu Peng, and Jian Shuisheng
The model of full vector Galerkin finite element method (FEM) with transparent boundary conditions (TBC) is established. The modal birefringence, confinement loss and dispersion of the fundamental mode of five kinds highly birefringent photonic crystal fibers (PCFs) with elliptical cores are analyzed and compared. The The model of full vector Galerkin finite element method (FEM) with transparent boundary conditions (TBC) is established. The modal birefringence, confinement loss and dispersion of the fundamental mode of five kinds highly birefringent photonic crystal fibers (PCFs) with elliptical cores are analyzed and compared. The modal birefringence of a photonic crystal fiber, which is formed by diminishing air holes along x-direction and enlarging air holes along y-direction in inner cladding, is 5.96×10-3 at the wavelength of 1550 nm, while that of a photonic crystal fiber with elliptical core is 1.52×10-3. The results show that high birefringence can be obtained by increasing the difference of air holes size along orthogonal direction in inner cladding. It is also proved that enlarged air holes of inner cladding reduce the confinement loss, and increase the dispersion, but the impact of diminished air holes is reversed; the fewer the air holes in inner cladding are, the flatter the dispersion is..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 559 (2008)
Effect of Ion Density on Slow Light Propagation in Erbium-Doped Optical Fiber
Ye Jianbo, Zhang Yundong, Qiu Wei, and Xu Huanwen
In the absorption spectrum of the medium, a burned hole is appeared by coherent population oscillation, and the linewidth of this feature is approximately the inverse of the ground state population recovery time. Based on the theoretical analysis of gain, the effect of absorption on the different pump powers is obtaineIn the absorption spectrum of the medium, a burned hole is appeared by coherent population oscillation, and the linewidth of this feature is approximately the inverse of the ground state population recovery time. Based on the theoretical analysis of gain, the effect of absorption on the different pump powers is obtained. In the medium absorption range, the oscillation leads the pulse to experience absorption saturation and propagation delay; in the medium gain range, this effect induces the pulse to experience gain saturation and propagation advance. Making use of coherent population oscillation we can control the group velocity of light propagation in erbium-doped optical fiber. According to coherent population oscillation and gain theory, the analytic expression of the group index from rate equation is obtained. In the experiment the slowest group velocity was 3.45×102 m/s, and the corresponding group index was 8.7×105. The simulation results are quantitatively coincident with the experimental data..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 563 (2008)
Loss Characteristics of Photonic Crystal Fiber as Terahertz Waveguide
Hu Jie, and Chen Heming
A new type of terahertz photonic crystal waveguide, whose clad made of silicon contains periodic circular air holes arranged as triangular lattice and core is polythene (PE), is presented. Bandgap distribution characteristic of this photonic crystal terahertz waveguide and how air-filling factors affect the bandgap disA new type of terahertz photonic crystal waveguide, whose clad made of silicon contains periodic circular air holes arranged as triangular lattice and core is polythene (PE), is presented. Bandgap distribution characteristic of this photonic crystal terahertz waveguide and how air-filling factors affect the bandgap distribution characteristic are investigated by plane wave method (PWM). Then loss characteristics of the photonic crystal terahertz waveguide with different parameters are computed by finite-difference frequency-domain method (FDFD). Results show that this waveguide is a sort of photonic band gap guiding fiber with good capability to transmit terahertz wave. With higher air-filling factors, larger spacing between air holes and more circular structures in the cladding layer, lower leakage loss could be achieved. The lowest loss could be less than 1.5 dB/km if parameters are chosen appropriately..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 567 (2008)
Design and Study on a New Fiber Sensor with Self-Repairing Functions
Li Peng, Zhao Zhimin, and Hong Xiaoqin
Fiber optic microbend sensors under the strong signal will bring about the fiber rupture, and the sensor will invalidate. To solve this problem, the self-repairing of the fiber optic microbend sensor was researched. A short wavelength light curing adhesive was designed. It has good optical, mechanical and adhesive perfFiber optic microbend sensors under the strong signal will bring about the fiber rupture, and the sensor will invalidate. To solve this problem, the self-repairing of the fiber optic microbend sensor was researched. A short wavelength light curing adhesive was designed. It has good optical, mechanical and adhesive performances. We put it into the hollow-center fiber embodied with fiber optical sensor. And an intelligent fiber optic microbend sensor with self-diagnosing and self-repairing functions was designed. Experimental results show this sensor has little repairing time, good repairing effect..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 573 (2008)
Analysis for the Reflective Spectrum Characteristics of Chirped Phase-Shifted Fiber Gratings
Lu Shaohua, Xu Ou, Dong Xiaowei, Liu Yan, Li Bin, and Jian Shuisheng
As a transmission type filter, chirped phase-shifted fiber grating has the advantage of low cost, which makes it a critical component in optical communication and sensor system. Reflective spectrum of chirped phase-shifted fiber grating is analyzed about the influence of phase shift and position on reflection characterAs a transmission type filter, chirped phase-shifted fiber grating has the advantage of low cost, which makes it a critical component in optical communication and sensor system. Reflective spectrum of chirped phase-shifted fiber grating is analyzed about the influence of phase shift and position on reflection characteristic by the transfer matrix method combined with resonance theory. Different characteristics from uniform phase-shifted fiber gratings are obtained: the transmission window is away from the center of the reflective spectrum and becomes shallow when the phase shift in the center of the grating is unequal to π/2; the transmission window varies with the location of the π/2-phase shift, but all the transmission windows are of the same depth. Numerical predictions agree well with the experimental results. Multiple phase shifts can be used to open several transmission windows with the same depth which makes chirped phase-shifted gratings have a good application prospect in multi-channel filter and dispersion compensator..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 577 (2008)
Performance Analysis of a Multimode Fiber Communication System Based on the Adaptive Modulation Orthogonal Frequency Division Multiplexing
Li Zhaoxi, Hu Guijun, and Kong Lingjie
With the development of short distance communication network, multimode fiber (MMF) has become a ideal medium to realize high-speed transmission of information with large-capacity. But the severe model dispersion of the MMF restrict its transmission ability. To improve the transmission ability of the MMF, a MMF communiWith the development of short distance communication network, multimode fiber (MMF) has become a ideal medium to realize high-speed transmission of information with large-capacity. But the severe model dispersion of the MMF restrict its transmission ability. To improve the transmission ability of the MMF, a MMF communication system based on adaptive modulation (AM) orthogonal frequency division multiplexing (OFDM) is designed. An adaptive bit loading algorithm which is fit for this communication system is proposed. Simulation is done to validate the feasibility of the algorithm. Based on the given system, the effect of adaptive modulation to the transmission performance of the system is emphatically analyzed. And the bit error rate (BER) curves of different bit rates, different transmission performance with and without adaptive modulation are compared. The result shows that adaptive modulation can improve the transmission performance of the system effectively, and overcome the effect of deep fading nulls very well..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 582 (2008)
Beam Transmission
Analysis of Laser Optimized Spectrum for Smoothing the Focused Spot by Temporal and Special Method
Li Ping, Ma Chi, Su Jingqin, Zhang Rui, Wang Fang, and Cheng Wenyong
For improving the uniformity of the focal spot in the inertial confinement fusion (ICF) experiments, we simulated the effects of the different spectral shapes of broadband light with the focused spot through phase plate, such as random phase plate (RPP) or continuous phase plate (CPP), and the uniform bandwidth and maxFor improving the uniformity of the focal spot in the inertial confinement fusion (ICF) experiments, we simulated the effects of the different spectral shapes of broadband light with the focused spot through phase plate, such as random phase plate (RPP) or continuous phase plate (CPP), and the uniform bandwidth and maximal dispersive angle. The power spectral density (PSD) and root mean square (RMS) of the focused spot intensity were used to evaluate smoothing effect. The results show that the optimized spectrum can improve smoothing efficiently, and the RMS can be improved by 43.7% compared with the sinusoidal phase modulated spectrum. Generally, the smoothing efficiency would be better if the weighting of the different spatial frequencies of the focused spot was considered to design phase plate..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 534 (2008)
Propagation Properties of Lorentz Beam Passing through First-Order Axisymmetric Optical Systems
Lu Qunying, Chen Tingting, Ding Guilin, and Yuan Xiao
Based on the generalized Huygens-Fresnel diffraction integral, the analytic propagation expressions for Lorentz beams passing through first-order axisymmetric optical system are derived. The expressions of the beam-width, Rayleigh distance and divergence angle of Lorentz beam are given, and their transform characteristBased on the generalized Huygens-Fresnel diffraction integral, the analytic propagation expressions for Lorentz beams passing through first-order axisymmetric optical system are derived. The expressions of the beam-width, Rayleigh distance and divergence angle of Lorentz beam are given, and their transform characteristics in free space are discussed. It is shown that the Rayleigh distance of Lorentz beams is larger than that of Gaussian beam. However, the expansion speed of the beam-width of Lorentz beams is lower than that of Gaussian beams and the far-field divergence angle of Lorentz beams is smaller than that of Gaussian beams. Moreover, the transfrom laws of the above parameters for Lorentz beams are the same as those for Gaussian beams passing through free space..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 539 (2008)
Calculated Methods of High Power Laser Near Field Parameters
Sun Zhihong, Peng Zhitao, Liu Hua, Xu Longbo, Zhao Junpu, Wang Chao, and Fu Xuejun
In order to scientifically evaluate the near field parameters involving the modulation and contrast ratio in space region for high power solid-state laser facility, the grey threshold of image segmentation in image processing is used to separate the noise and signal for the image of near field picked by CCD. The maximuIn order to scientifically evaluate the near field parameters involving the modulation and contrast ratio in space region for high power solid-state laser facility, the grey threshold of image segmentation in image processing is used to separate the noise and signal for the image of near field picked by CCD. The maximum square difference value is taken as the main criterion for noise threshold. The grey background can be obtained from the grey value of the most probability in the noise region. The oddity spot in laser near field can be judged based on whether the intensity is greater than Iavg(1+5σ) or not. The image smoothness technique of eight neighbor regions is adopted to process the oddity spots of pixel. Two evaluated methods for modulation are analyzed and compared with many experimental data. It is shown that two calculation results of modulation are identical, and present evaluated methods of high power laser near field parameters are much more normative..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 544 (2008)
Measurement of Temporal Depending Lasing Modes of a High Power Transverse-Flow CO2 Laser Processor
Cheng Cheng, Ma Xingchao, Xu Zhousu, Wang Wenpeng, and Yao Jianhua
The transverse modes of a high power transverse-flow CO2 laser are on-line measured by using a laser beam analyzer. The temporal evolution of the transverse modes is observed also. The output beams are characterized with “double mode”, i.e., two higher-order modes spacing 8 mm between the mode centers, and overlapping The transverse modes of a high power transverse-flow CO2 laser are on-line measured by using a laser beam analyzer. The temporal evolution of the transverse modes is observed also. The output beams are characterized with “double mode”, i.e., two higher-order modes spacing 8 mm between the mode centers, and overlapping unsymmetrical configurations. There is evidence to whow that such “double mode” arises from a misaligned axes of the resonator consisting of two tandem resonators, and a distorted cathode-copper tube. The transverse mode are more degenerated into complicated shapes as the lasing operating duration increases. An initial investigation shows that the temporal evolution of the modes depends on the gaseous component varying in the resonator during the lasing operation..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 549 (2008)
Nonlinear Network of Measuring Transverse Modes in a Laser Beam
Shen Jinhua, Wang Shiyu, Guo Zhen, Wen Jianguo, and Cai Defang
The distribution of transverse modes of the laser, especially the ratio of fundamental mode is proposed to evaluate laser beam quality, and the measuring method is studied. The beam spot images captured by a CCD detector are input into a nonlinear network which bases on the Hopfield network principle. The dynamics steaThe distribution of transverse modes of the laser, especially the ratio of fundamental mode is proposed to evaluate laser beam quality, and the measuring method is studied. The beam spot images captured by a CCD detector are input into a nonlinear network which bases on the Hopfield network principle. The dynamics steady state is obtained by computing the energy function of the network and performing training arrangement. The proportion of all ranks of transverse mode in the steady state is the measurement result. During the experiment, a laser diode-pumped solid-state laser was used to emit laser beam, and the captured beam spot images were input into the nonlinear network after image processing, and the proportion of fundamental mode was 69%. The results were used to compose a new spot digital image, and the relative error compared the original image was 3.53%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 555 (2008)
Biomedical Photonics and Laser Medicine
Generation of Antitumor Vaccines for H22 Tumor on Mouse Using Photodynamic Therap
Zhang Hongyu, Ma Wenjiang, Zou Zhaohui, Gao Weiping, Xue Zhixiao, and Li Yingxin
To test the contribution of the direct effects of photodynamic therapy (PDT) on tumor cells, we examined the immunogenicity of PDT-generated murine tumor cell lysates in a preclinical vaccine model. Sixty Kunming mice (H22 tumor host) were divided into two groups randomly and equally. Six to twelve-week-old Kunming micTo test the contribution of the direct effects of photodynamic therapy (PDT) on tumor cells, we examined the immunogenicity of PDT-generated murine tumor cell lysates in a preclinical vaccine model. Sixty Kunming mice (H22 tumor host) were divided into two groups randomly and equally. Six to twelve-week-old Kunming mice were vaccinated intradermally on the right shoulder with 50 μL lysates (3×105 cell equivalents) for experimental group or medium control for control group every three days during two weeks. The mice rested a week and then inoculated on the flank with 1×106 tumor cells harvested from exponentially growing cultures. And then we compared antitumor rate, survial rate and relevant indicators of immunology between two groups. PDT vaccines could inhibit the tumor growth rate compared to the contrast group. The tumor inhibition rate of PDT vaccines group was 60% and long-term available. The survival rate of PDT vaccines group at 100 day was 56% which was significantly higher than contrast group. Our studies suggest that PDT-generated vaccines could effectively inhibit tumor growth, improve survival rate of mice in experimental group, and enhance antitumor immune response significantly. PDT-generated vaccines may have well clinical potential as an adjuvant therapy..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 631 (2008)
Signal-to-Noise Ratio Analysis and Optimization of Optical Coherence Tomographic Imaging System
Li Peng, and Gao Wanrong
In order to increase the signal-to-noise ratio (SNR) and improve the detection sensitivity of the optical coherence tomographic (OCT) system, the main noise sources in the OCT system are analyzed in detail. A theoretical noise model is then proposed which may be used to analyze the effect of different parts of OCT systIn order to increase the signal-to-noise ratio (SNR) and improve the detection sensitivity of the optical coherence tomographic (OCT) system, the main noise sources in the OCT system are analyzed in detail. A theoretical noise model is then proposed which may be used to analyze the effect of different parts of OCT system. Based on the theoretical results, the performance of an OCT imaging system is analyzed. Through measuring the noise level of the system, the experimental model of the system noise is obtained, and then it is used to correct the theoretical analysis results. Based on the above analysis, the imaging performance of the OCT device is optimized. The axial resolution of 16 μm, and the detection sensitivity of -90 dB have been obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 635 (2008)
Laser Manufacturing
Laser Heat Treatment and Wear Resistance of Electroless Plating Ni-P-Nano-Al2O3 Composite Coatings
Zheng Xiaohua, Song Renguo, and Yao Jianhua
The Ni-P-nano-Al2O3 composite coatings were prepared onto medium carbon steel substrates by electroless plating method. The transverse-flow CO2 laser was employed for the heat treatment of the coatings at various scan velocities and power densities. The composition, microstructure, morphology, adhesion to the substrateThe Ni-P-nano-Al2O3 composite coatings were prepared onto medium carbon steel substrates by electroless plating method. The transverse-flow CO2 laser was employed for the heat treatment of the coatings at various scan velocities and power densities. The composition, microstructure, morphology, adhesion to the substrate and wear resistance of the coatings were characterized by energy dispersive X-ray spectrum (EDS), scanning electron microscopy (SEM), X-ray diffraction (XRD), scratch test and friction and wear test (ball-on-disk). The effects of process parameters on microstructure and wear resistance of the coatings were investigated. It is found that the laser heat treatment conduces the microstructure from amorphous to crystalline structure, which comprises Ni3P and Ni phase, and Al2O3 phase remaines amorphous; the hardness of the coatings increases obviously for the phase transformation hardening. The friction coefficient increases due to the transformation of phase structure and the raise of surface roughness of the coatings, and the adhesion to the substrate decreases slightly. The main operating wear mechanism is abrasion. By treating with scan velocity 1.5～3.0 m/min, power density 5.0～8.3 kW/cm2, the coatings show high hardness, good wear resistance and a minimum wear rate of 1.21×10-5 mm3/(N·m)..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 610 (2008)
Offset Interference of Laser TV
Kang Yusi, Liu Weiqi, Feng Rui, and Zhang Jian
In the laser video display system, video image with low contrast and inferior image quality are usually happened due to the effects of the background interference fringes. Aiming at eliminating such kind of interference fringes, multi-pixel scanning method is proposed in the laser TV, which breaks the technical bottlenIn the laser video display system, video image with low contrast and inferior image quality are usually happened due to the effects of the background interference fringes. Aiming at eliminating such kind of interference fringes, multi-pixel scanning method is proposed in the laser TV, which breaks the technical bottleneck of scanning method. What is more, compared with traditional display, a great improvement can be fulfilled in image quality. Through deep analysis and research on the mechanism of laser interference in the process of laser display, a multi-pixel scanning method is presented in this paper, and relevant device has also been designed. This method can be used to achieve offset interference as well as projecting display. It can been seen that excellent display effect can be obtained by this method and technical defection in scanning laser display can be overcome as well as laser interference fringes in projecting style. It is demonstrated that this method has referenced and practical evaluation for offering an effective method in the research of laser TV..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 615 (2008)
Ceramic Phase Reinforcing Co-Alloy Coating with Laser Inducing In-Situ Synthesis on the Surface of Copper Alloy
Li Huili, Chen Suiyuan, Liu Daliang, and Liu Changsheng
Using Co-based alloy coating powder containing certain amount of nano-Al powder, the ceramic phase reinforcing Co-based alloy coating was produced by pulse laser overlapping in-situ synthesis on the surface of Cu-Cr alloy for crystallizer. The structure and forming mechanism of the coating were studied by means of optiUsing Co-based alloy coating powder containing certain amount of nano-Al powder, the ceramic phase reinforcing Co-based alloy coating was produced by pulse laser overlapping in-situ synthesis on the surface of Cu-Cr alloy for crystallizer. The structure and forming mechanism of the coating were studied by means of optical microscope , X-ray diffraction (XRD), scan electronic microscope and micro-hardness tester. The results show that the ceramic phase reinforcing Co-based alloy coating is produced on the surface of Cu-Cr alloy and the interface get metallurgical bonding between the Co-based alloy coating and Cu-Cr alloy substrate by using the optimized technological parameters of laser (current of 175 A, frequency of 15 Hz, pulse width of 3 ms, scan rate of 4.0 mm/s) and overlapping rate (20%～25%). The maximal size of the ceramic particles by in-situ synthesized is about 3 μm. Most of the ceramic particles are regular shape as ball and dispersive distribution. The principle of the Co-based alloy forms crystalline is that the ceramic phase as the center promotes the liquid Co-based alloy around it to be crystalline, and the crystallinic alloy enwrapps the ceramic phase. This process controls the aggregation of the ceramic phase, which causes the particles dispersive and small. The hardness of Co-based alloy coating (300HV) was improved obviously compare with that of Cu-Cr alloy substrate (94HV)..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 620 (2008)
Residual Stress Analysis of the Remelting Zone on 42CrMo Steel Plate in Single-Pass Laser Wide-Band Treatment
Zhan Huanxiao, Wang Yong, Han Tao, and Han Bin
Based on SYSWELD finite element code, a three-dimensional finite element model for laser remelting process was created, the wide-band heat source model implemented by a FORTRAN subroutine was developed to simulate the single-pass laser wide band remelting process on 42CrMo steel, and predict residual stresses of the reBased on SYSWELD finite element code, a three-dimensional finite element model for laser remelting process was created, the wide-band heat source model implemented by a FORTRAN subroutine was developed to simulate the single-pass laser wide band remelting process on 42CrMo steel, and predict residual stresses of the remelting zones with different technological parameters were estimated and analyzed. The thermal cycle was measured by temperature measuring equipment and phase transformation was observed by scanning electron microscopy (SEM). The results showed that technological parameters has a great influence on the residual stress distribution of the remelting zone, the superficial processability of the laser remelting zone is bad whether the laser energy input density is too high or too low. The favorable residual compressive stress in the remelting zone can be achieved when the laser output power is 3500 W, the scanning rate is ranged from 600 mm/min to 1000 mm/min, that is, the energy input density is within 20.9～35.0 J/mm2. After the processing, the initial ferrite-pearlite microstructure of the matrix is transformed to martensite phase with the proportion higher than 95%..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 625 (2008)
Laser Physics
Backscattering Enhanced Characteristics of Supercontinuum Emission from a Self-Guided Filament in Air
Zhang Liwen, Lin Chen, Xin Li, and Gao Junyi
New characteristics of supercontinuum emission generating along with ultrashort femtosecond laser self-guided propagating in air, such as ultra wide band spectrum and backscattering enhancement, produce a new study field for the development of atmosphere detection lidar. The backscattering properties of supercontinuum New characteristics of supercontinuum emission generating along with ultrashort femtosecond laser self-guided propagating in air, such as ultra wide band spectrum and backscattering enhancement, produce a new study field for the development of atmosphere detection lidar. The backscattering properties of supercontinuum emission from a self-guided filament generated by femtosecond laser are researched by measuring the angular distribution of supercontinuum emission at different conditions of air. The results show the backscattering of supercontinuum emission from a filament is enhanced in clear air and dusty air with aerosol. And by fitting the experimental data of the backscattering of supercontinuum emission, it is found that the angular distribution of supercontinuum backscattering satisfy Lorentz function; in clear air the angle width is 6.4°, the normalized backscattering intensity increases 3.2 times as compared with Rayleigh scattering at 180°. Along the filament, the frontward supercontinuum emission exhibits the conical emission, so frontward scattering is obviously dependent on wavelengths; the backward scattering shows no obvious dependence on wavelengths..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 519 (2008)
Transition Radiation from the Surface in Femtosecond Laser Interaction with Solid Targets
Wang Guangchang, and Zheng Zhijian
For studying transport of hot electrons in solid targets by transition radiation (TR), the image pattern of spatial distribution and spectrum of optical emission were measured at the normal direction from the rear side of targets employing optical charge coupled device (CCD) camera and optical multi-channel spectrometeFor studying transport of hot electrons in solid targets by transition radiation (TR), the image pattern of spatial distribution and spectrum of optical emission were measured at the normal direction from the rear side of targets employing optical charge coupled device (CCD) camera and optical multi-channel spectrometer apparatus (OMA) on the 100 TW femtosecond laser facility. The image pattern of spatial distribution presents a tray-shape and in the tray-shape there is a bright localized signal, which shows filament effect during hot electron transport. The spectrum of optical emission presents a sharp peaks in the wavelength near 800 nm, which is attributed to the one-order harmonic (ω0). The production of one-order harmonic is ascribed to the coherent transition radiation (CTR) generated by microbunches produced in the transporting of hot electron beams. The red shift is caused by the expansion of the critical density surface. With the increase of the laser energy, the peak of the CTR moves further to the long wavelength side. Intensity of transition radiation decreases with the increase of the target thickness..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 524 (2008)
Experimental Research of Near Resonant Energy Transfer from SiO(b3П) to Na
Wang Zengqiang, Duo Liping, Sang Fengting, and Jin Yuqi
The near resonant energy transfer from SiO(b3П) to Na is one of the most important processes of the chemical sodium atom laser. In order to research the process, an experimental device of near resonant energy transfer, which includes a system of synthesizing SiO(b3П) and a system of producing and carrying sodium vapor,The near resonant energy transfer from SiO(b3П) to Na is one of the most important processes of the chemical sodium atom laser. In order to research the process, an experimental device of near resonant energy transfer, which includes a system of synthesizing SiO(b3П) and a system of producing and carrying sodium vapor, was set up. The metastable state energy storage particle—SiO(b3П) was synthesized by the reaction of products of silane pyrolysis and N2O. Based on these works, the experimental research of energy transfer from SiO(b3П) to Na has been done. The spontaneous emission spectra of SiO(b3П) and Na(4d2D) was detected; the existence of the near resonant energy transfer from SiO(b3П) to Na and the existence of Na(4d2D) were testified. The further research showed that under the experimental conditions of the flow rate of SiH4 at 0.09 mmol/s, the flow rate of SiH4 buffer gas at 14.88 mmol/s, the flow rate of N2O at 0.744 mmol/s, and the pyrolysis temperature of SiH4 at 1350 K, when the flow rate of Na buffer gas (7.44 mmol/s) is fixed, the density of Na(4d2D) increases with the rise of the temperature of Na oven; and when the temperatures of Na oven (673 K and 723 K respectively) are fixed, the density of Na(4d2D) increases with the rise of the flow rate of Na buffer gas almost linearly. This work provides a preparation for the further research of this laser system, such as the measurement of signal gain and performance of lasing..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 529 (2008)
Materials and Thin Films
Laser Performance of Er3+:Yb3+:GdAl3(BO3)4 Crystal at 1.5～1.6 μm
Chen Yujin, Lin Yanfu, Gong Xinghong, Luo Zundu, and Huang Yidong
An Er3+:Yb3+:GdAl3(BO3)4 (GAB) crystal with Yb3+ and Er3+ atoms fraction of 20% and 1.1% was grown by the flux method. End-pumped by a fiber-coupling quasi-continuous wave (CW) diode laser at 0.97 μm, 1.5～1.6 μm laser with output power up to 1.75 W and slope efficiency near to 20% was realized from a 0.7 mm thick Er3+:An Er3+:Yb3+:GdAl3(BO3)4 (GAB) crystal with Yb3+ and Er3+ atoms fraction of 20% and 1.1% was grown by the flux method. End-pumped by a fiber-coupling quasi-continuous wave (CW) diode laser at 0.97 μm, 1.5～1.6 μm laser with output power up to 1.75 W and slope efficiency near to 20% was realized from a 0.7 mm thick Er3+:Yb3+:GAB crystal in a hemispherical cavity with the output coupler transmission of 1.5%. The influences of the absorbed pump powers and output coupler transmissions on the laser spectra were also investigated. When the output coupler transmission was 1.5% and the absorbed pump power was increased, more longitudinal mode groups were observed and the main output laser power gradually shifts from the longitudinal mode group around 1.60 μm to around 1.55 μm. When the absorbed pump power was 13.6 W and output coupler transmission was increased, laser wavelength was shifted from 1.60 μm to 1.52 μm. The results show that the Er3+ and Yb3+ co-doped GAB crystal is an excellent gain medium for realizing 1.5～1.6 μm laser..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 597 (2008)
Judd-Ofelt Analysis of Spectroscopic Properties of Tm3+ Doped Lu2SiO5 Crystals
Yao Baoquan, Zheng Liangliang, Zhao Guangjun, and Zong Yanhua
A new silicate laser crystal, Tm:Lu2SiO5 (Tm:LSO) crystal, has been obtained by the Czochralski technology. Absorption spectra and fluorescence (un-polarized) spectra of Tm:LSO have been measured at room temperature. Parameters such as Judd-Ofelt intensive parameters, oscillator strength, spontaneous radiation rate, flA new silicate laser crystal, Tm:Lu2SiO5 (Tm:LSO) crystal, has been obtained by the Czochralski technology. Absorption spectra and fluorescence (un-polarized) spectra of Tm:LSO have been measured at room temperature. Parameters such as Judd-Ofelt intensive parameters, oscillator strength, spontaneous radiation rate, fluorescence lifetime, integrated absorption cross-section, integrated emission cross-section were calculated by Judd-Ofelt theory. Intensive parameters were calculated to be Ω2=9.1355×10-20 cm2, Ω4=8.4103×10-20 cm2, Ω6=1.5908×10-20 cm2. Some main emission peaks exist around 1.9 μm, corresponding to 3F4→3H6 transition. Fluorescence lifetime and integrated emission cross-section, corresponding to 3F4→3H6 transition, were calculated to be 2.03 ms and 5.81×10-18 cm2, respectively. Laser actions have been obtained by use of Tm:LSO crystal at the temperature of 77 K. The central laser wavelength of 1960 nm and pumping threshold of 2.13 kW/cm2 were obtained..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 601 (2008)
Sensitization of Ce3+ Ions Co-doped in Zinc Tungstate Laser Crystals Doped with Nd3+ or Eu3+ Ions
Zhang Qinhui, Liu Bo, and Xu Yuheng
In order to study the sensitization of Ce ions co-doped in ZnWO4 laser crystals doped with Nd or Eu ions, macro-defect-free Nd:ZnWO4, Ce:ZnWO4, Eu:ZnWO4, Ce:Nd:ZnWO4 and Ce:Eu:ZnWO4 crystals were grown by the Czochralski method. The X-ray diffraction (XRD), absorption spectrum and fluorescence spectrum of the crystals In order to study the sensitization of Ce ions co-doped in ZnWO4 laser crystals doped with Nd or Eu ions, macro-defect-free Nd:ZnWO4, Ce:ZnWO4, Eu:ZnWO4, Ce:Nd:ZnWO4 and Ce:Eu:ZnWO4 crystals were grown by the Czochralski method. The X-ray diffraction (XRD), absorption spectrum and fluorescence spectrum of the crystals were measured. The results of measurement indicated that the strong absorption of Ce3+ ions in ZnWO4 crystals at 324 nm can absorb pump energy effectively and the energy transfer exists between Ce3+ ions and Nd3+ ions as well as Eu3+ ions obviously. It enhances the intensities of the up-conversion fluorescence (at 474 nm and 572 nm) of Nd3+ ions and the fluorescence (at 613 nm) of Eu3+ ions. The sensitization mechanism and the energy transfer processes are presented. The results demonstrated that the sensitization of Ce ions co-doped in ZnWO4 laser crystals doped with Nd or Eu ions has better performance on enhancing the luminescence intensity of laser crystals..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 605 (2008)
Measurement and Metrology
Novel Method of the Wavelength Determination of Spectral Lines with Planar Crystal Spectrometer
Zhao Yang, Yang Jiamin, Zhang Jiyan, Liu Jinsong, Yuan Xiao, Wei Minxi, Hu Zhimin, and Gan Xinshi
For the need of X-ray wavelength determination of laser plasma, based on the auxiliary diaphragm method, a novel method was presented for the wavelength determination of the X-ray spectral lines measured with planar crystal spectrometer in theory. We develop an improved method to determine the distance from the crossinFor the need of X-ray wavelength determination of laser plasma, based on the auxiliary diaphragm method, a novel method was presented for the wavelength determination of the X-ray spectral lines measured with planar crystal spectrometer in theory. We develop an improved method to determine the distance from the crossing line of crystal and recording plane to the first auxiliary diaphragm, and curvature of spectral line is used to determine the angle between crystal and recording plane. In normal auxiliary diaphragm method, reference line is used to determine the two parameters. However, we can obtain wavelengths for all recording spectral lines without any reference lines by using this method. In practical use, the precision of wavelength determination can achieve 1×10-3 nm by increasing the distance between two diaphragms and adjusting the relative position between crystal and recording plane..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 587 (2008)
Spatial-Carrier Phase-Shifting Algorithm Based on Least-Squares Iteration
Xu Jiancheng, Xu Qiao, and Chen Jianping
An advanced spatial-carrier phase-shifting (SCPS) algorithm based on least-squares iterative procedure is proposed to cope with the errors caused by the uncertainty of spatial carrier frequency. The algorithm divides the randomly spatial carrier interferogram into four randomly phase-shifted interferograms and then obtAn advanced spatial-carrier phase-shifting (SCPS) algorithm based on least-squares iterative procedure is proposed to cope with the errors caused by the uncertainty of spatial carrier frequency. The algorithm divides the randomly spatial carrier interferogram into four randomly phase-shifted interferograms and then obtains the phase distributions by a least-squares iterative procedure. The algorithm provides stable and fast convergence, high spatial frequency resolution and accurate phase extraction with only one single randomly spatial carrier interferogram. The results of computer simulation and experiment show that the accuracy is better than λ/20 (peak value, PV) and λ/200 (root mean square, RMS) with about 10 times iterations and it is better than that obtained by the fast Fourier transform (FFT) algorithm. Computer simulations also show that the accuracy of the algorithm can be improved by increasing the spatial carrier frequency and making the direction of the carrier near 45° or 135°..
Chinese Journal of Lasers
- Publication Date: Jan. 01, 1900
- Vol. 35, Issue 4, 592 (2008)
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