通过对行波放大器储能及小信号增益进行理论计算, 模拟出输出激光特性, 即随着放大器泵浦电流的增加, 放大器增益介质内储存能量和小信号增益系数快速增长,提取效率达到76%以上.输出能量随放大器泵浦电流的增加, 呈线性增长趋势, 在泵浦电流为80 A时, 输出光能量逐渐饱和, 最大输出能量为798 mJ.实验中, 放大器入射光源采用脉冲能量为350 mJ、重复频率为10 Hz、脉宽为10 ns的脉冲激光, 放大器中的Nd∶YAG晶体棒尺寸为Φ7.5 mm×134 mm, Nd3+的掺杂浓度为1.1%, 泵浦功率最大24 kW,使用三个最大功率为66 W的半导体制冷器进行半导体热电制冷,在重复频率为10 Hz, 泵浦电流为80 A, 泵浦脉冲宽度为200 μs时, 获得了最大脉冲能量为700 mJ、脉冲宽度为10 ns的激光输出,通过光束质量诊断仪M-200S测得输出光束在水平和垂直两个方向的光束质量分别是7.9和12.4.

Based on theoretical calculation of the stored energy and small-signal gain coefficient of the travelling wave amplifier, the characteristics of the output laser were simulated. With the increment of the pumping current, the stored energy and small signal gain coefficient increase rapidly. And amplifier energy extraction efficiency can reach more than 76%. In terms of the output energy, it rises linearly with the increasing of the pumping current. When the pumping current is 80 A, a 798 mJ laser pulse can be obtained. Related experiment is carried out on the basis of theoretical simulation. In this experiment, a pulse with 350 mJ energy, 10 Hz repetition frequency, 10 ns width is used as the seed. The size of the Nd∶YAG crystal rod in amplifier is Φ7 mm×134 mm and the doping concentration is 1.1 at%. The maximum peak power of laser diode (LD) is 24 kW. In order to control the temperature of the crystal working environment, three thermoelectric coolers are chosen with a maximum power of 66 W. Ultimately, a 700 mJ, 10 ns, 10 Hz laser pulse is obtained for single-pass amplification. The beam qualities of horizontal and vertical direction are 7.9 and 12.4, respectively, measured by the beam quality diagnostic instrument M-200S.