激光成像跟踪系统是实现空间远距离暗目标跟踪的一种极具潜力的手段，而目标在激光照射下的图像将受到激光散斑的调制作用，影响目标的识别及目标的定向精度。对激光照射下的目标图像的统计特性进行了理论分析，提出了一种对原始图像依次实施灰度线性变换、中值滤波和Lee滤波的组合数值滤波器对图像噪声进行抑制。处理的结果表明，采用上述组合方法，图像的噪声指数可从0.67降至0.22，同时边缘保持度可达0.96，为后续的图像处理提供了必要的条件。

在充分考虑了空间背景光辐射特性以及漫反射目标对相干光和自然光的不同反射特性的基础上,利用信号检测的统计学方法,导出了空间电荷耦合器件(CCD)凝视成像跟踪系统分别在激光照明主动跟踪模式和太阳光照明被动跟踪模式下的作用距离表达式。结果表明,空间CCD凝视成像跟踪系统在脉冲能量为1 mJ的激光照明主动跟踪模式下可对1 m2空间漫反射目标实现10 km量级范围内的跟踪;而利用太阳光照明的被动跟踪模式下的跟踪距离可达几百千米。

Space debris distribute in a large range in the space, and their size are very different. For the purpose of detecting the small space debris, the space-based laser radar is used. The characteristics of the background radiation in space are analyzed at first. Then, according to the analog and digital detection theory of laser radar, with avalanched photodiode as the detector, the minimal detectable laser powers are calculated. Based on the radar equation, the detection ability of laser radar is got. The result indicates that the space-based laser radar is effective to detect the small space debris in a specific range.

A laser diode (LD) stack pumped solid-state laser (DPL) with different cooling conditions was reported. The thermal lens was calculated and compared under different cooling conditions. The influence of the thermal lens effect on the output energy fluctuation of the DPL was studied. The LD stacks peak power was 12 kW with 1-kHz repetition frequency and 20% duty ratio. In the examination with nothing to cool the solid-state heat capacity laser (SSHCL), the output power was 1 J at the beginning, after 1 s it fell down to 50%, and with the water cooling the output power hardly fell down.

A new method is proposed which makes it possible to produce flattened irradiance distribution by incoherent combination of cosh Gaussian beams with different parameters. Based on the Collins integral formula, the resulting irradiance distribution is derived and the corresponding beam qualities in terms of M2 factor and kurtosis parameter are given. The numerical examples illustrate that a flattened intensity distribution of the resulting beam can be obtained in the near filed if appropriate parameters are chosen. Compared with the coherent combination of the Hermite-Gaussian (HG) beams, this new method leads to better beam quality and can be more easily realized experimentally resulting from in-phase-free requirement.

Intracavity phase locking of two beams emitting from a block of Nd:YAG medium side-pumped by laser diode array (LDA) was investigated experimentally. The interference fringes of the two beams occured at the output mirror. The coherent output power of 1.13 W was obtained with combination efficiency of 64.9% and coherence degree of about 60%. Only a metallic wire as a filter located at a suitable position close to the output mirror can efficiently lock the entire structure with less than 8% power loss.

A novel dual-slab laser with an off-axis one-sided stable-unstable resonator which can compensate for thermal distortion to some extent by flipping the optical beam is described in this paper. The output power, efficiency, and near-field and far-field intensity distributions of the dual-slab laser have been studied. The results indicate that the novel dual-slab laser has better performance than the normal dual-slab laser with the same off-axis one-sided stable-unstable resonator.

A novel double-slab Nd:YAG laser, which uses face-pumped slab medium cooled by liquid with different temperatures on both sides, is proposed. The thermal distortion of wavefront caused by the non-uniform temperature distribution in the laser gain media can be self-compensated. According to the method of operation, the models of the temperature distribution and stress are presented, and the analytic solutions for the model are derived. Furthermore, the numerical simulations with pulse pumping energy of 10 J and repetition frequencies of 500 and 1000 Hz are calculated respectively for Nd:YAG laser medium. The simulation results show that the temperature gradient remains the approximative linearity, and the heat stress is within the extreme range. Then the absorption coefficient is also discussed. The result indicates that the doping concentration cannot be too large for the high repetition frequency laser. It has been proved that the high repetition frequency, high laser beam quality, and high average output power of the order of kilowatt of Nd: YAG slab laser can be achieved in this structure.

Ray-tracing method is used to simulate the distribution of absorption in crystal rod for different sidepumping configuration. The distribution of pumping power and absorption efficiency is compared, and the numerical results are presented. The results show that the more uniform pumping and the higher absorption coefficient are obtained with a diffuse cavity. And the method of the slow axis of laser diode stack perpendicular to the axis of lasing gives the higher central pumping density.

本文从理论上分析了利用调制的单模激光场共振激发来测量原子或分子的寿命.结果表明:感生荧光或共振荧光信号与调制信号间的相移主要来自三个过程:(1)由原子的横向弛豫时间及激光线宽决定的激发过程;(2)由激发能级及其他能级上粒子数衰减过程;(3)与系统达到平衡态粒子数分布所需的弛豫时间有关的碰撞激发过程.讨论了在不同的情况下它们的影响,并在分析中考虑了多普勒加宽的影响.