基于主振荡功率放大结构, 采用特殊取向Nd∶YAG激光放大器, 获得高脉冲能量、高光束质量的激光输出。激光放大结构包含种子源、预放大级和主放大级三部分。在主放大级中, 采用串联放置的激光二极管侧面抽运Nd∶YAG棒状放大模块对种子光进行放大。为了获得高光束质量的输出光束, 对不同切割方向Nd∶YAG晶体棒的热退偏损耗进行了模拟。根据模拟结果, 放大模块选择［100］切割方向的Nd∶YAG晶体棒作为增益介质。在重复频率为200 Hz、脉宽为25 ns、脉冲能量为40 μJ、光束质量接近衍射极限的种子光注入条件下, 获得了425 mJ脉冲能量输出, 输出光光束质量因子为1.37, 功率稳定度为0.81%。

Based on master-oscillator power amplifier structure, an laser output with high pulse energy and high beam quality is achieved using a specific orientation Nd∶YAG laser amplifier. The laser amplifier includes three parts, a seed laser source, a pre-amplifier stage and a main-amplifier stage. In the main-amplifier stage, a laser diode side-pump Nd∶YAG rod amplifiers is used for the amplification of the seed laser. In order to obtain a high beam quality output, the thermal depolarization losses for different cut Nd∶YAG rods are simulated. According to the simulation results, the ［100］-cut Nd∶YAG rods are chosen as the active materials in the main-amplifier stage. Under the condition of repetition frequency of 200 Hz, pulse width of 25 ns, pulse energy of 40 μJ and a near diffraction limit seed laser injected, an output of 425 mJ pulse energy is gained with a beam quality factor of 1.37, and the output power stability of 0.81%.