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

a）LD泵浦固体激光器具有高重复频率、高效率、高平均功率输出的特点，是惯性聚变动力装置激光驱动器的理想选择。发展高功率固体激光器的关键问题是减小激光输出的热畸变。本论文的主要工作是分析LD泵浦固体激光器的热效应，并研究补偿热效应的新技术。为此，采用STREAM软件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软件，用于激光系统的设计。B）对激光二极管（LD）抽运Nd：玻璃（HAP 4）激光器激射（在1054nm处）和在无激射条件下 ...更多信息 .由于受激发射损耗了晶体的储能，在激光条件下，晶体的热双折射减小。通过在两个相同的LD泵浦的钕玻璃棒之间插入一个90 °的石英旋转器，实现了几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分析。观察到功率损耗从补偿前的超过12%到补偿后的小于0.4%的显著降低。在考虑由于热双折射引起的功率损耗后，该激光器的输出性能与估计相当好地一致。为了获得高的能量提取效率和良好的光束质量，研制了YAG锯齿形板条激光放大器。在初始小信号增益为3.36的情况下，该激光器的能量提取效率高达73%。获得了1.2的优良光束质量因子M平方。利用90 °石英旋转器成功地补偿了放大器的热双折射。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