Study on the Control of Thermal Birefringence in the Laser-Diode Pumped Solid-State Laser Driver

A)LD泵浦的固体激光器有望在高重复频率下获得高平均功率、高效率的激光输出，是惯性聚变电站激光驱动器的一种很有前途的候选者。减小激光输出的热致失真是发展高功率固体激光器的关键问题。本论文的主要工作是分析LD泵浦固体激光器的热学特性，并开发新的热效应补偿技术。为此，利用STREAM模拟程序计算了激光系统中的温度分布，并开发了一个计算热致双折射空间分布的程序，并将其应用于激光系统的设计中。b)我们对激光二极管(LD)泵浦的掺钕玻璃(1054 Nm)激光系统中的二维热双折射分布进行了高灵敏度的测量，并在无激光条件下进行了…更多。在激光条件下，由于受激辐射耗尽了存储能量，降低了热双折射。通过在两根完全相同的LD泵浦的钕玻璃棒之间插入一个90度石英旋转器，实现了近乎完美的双折射补偿。利用琼斯矩阵法对热双折射引起的功率损耗进行了定量计算。在考虑了热双折射引起的功率损失后，激光器的输出性能与预估值吻合较好。c)为了获得较高的能量提取效率和良好的BCAM质量，提出了一种激光二极管抽运的八通1064 nm NdYAGZ字型板条激光放大器的新型激光器结构。在初始小信号增益为3.36的情况下，获得了高达73%的激光模体积能量提取效率。获得了优良的光束质量因子M的平方为1.2。利用90度石英旋转器成功地实现了该放大器的热双折射补偿。较少

a) An LD pumped solid state laser is expected to deliver high average laser power output with high efficiency at hight repetion rate and is a promising candidate of laser driver for an inertial fusion power plant. The key issue in the development of high power solid state laser is to reduce the thermally induced distortion of laser output. The main efforts of this study are aimed to analyze the thermal properties of LD pumped solid state laser and to develop the new techniques to compensate for the thermal effects. For these purposes, the temperature distributions in the laser system were calculated by the simulation code named STREAM,and a code to calculate the spatial distribution of thermally induced birefringence was newly developed and applied to the design of laser system.b) We performed the high-sensitivity measurements of two-dimensional (2D) thermal birefringence distribution in a laser-diode (LD) Pumped Nd : glass (HAP4) laser lasing (at 1054nm) and under no lasing conditions … More . The thermal birefringence was reduced under the lasing condition owing to the depletion of stored energy by stimulated emission. By inserting a 90 degree quartz rotator between two identical LD pumped Nd : glass rods, almost perfect birefringence compensation was achieved. The power loss due to thermal birefringence was evaluated quantitatively using the Jones matrix method. A considerable reduction of power loss, from over 12% before compensation to less than 0.4% after compensation, was observed the output performance of this laser was in fairly good agreement with the estimation after taking into account the power loss due to thermal birefringence.c) A novel laser architecture of laser-diode pumped eight pass 1064-nm Nd : YAG zig-zag slab laser amplifier was developed aming to achieve high energy extraction efficiency and good bcam quality. A high energy extraction efficiency of upto 73% for the laser mode volume has been achieved in this amplififier operating at an initial small signal gain of 3.36. The excellent beam quality factor M squared of 1.2 has been obtained. The compensation of thermal birefringence in this amplifer was successfully performed using a 90 degree quartz rotator. Less