对激光二极管端面抽运NdYAG/Cr4+∶YAG/YAG键合晶体的1 064 nm被动调Q激光性能进行了研究.对比分析了Cr4+∶YAG晶体初始透过率分别为84.9%和90.6%的调Q激光输出特性, 以及不同耦合输出镜透过率对调Q性能的影响.结果表明, 在特定抽运功率下, 各输出特性参数的优化(高输出功率, 高重复频率, 窄脉冲宽度)分别对应一个最佳的输出镜透过率; 随着抽运功率增加, 对应最佳的输出镜透过率越大.对比两种初始透过率的Cr4+∶YAG晶体对应的激光输出特性, 84.9%初始透过率的晶体获得相对较低的平均输出功率, 但相应的重复频率较小, 脉冲宽度窄, 使得调Q激光的峰值功率明显提高.采用30%透过率的耦合输出镜和10.4 W入射抽运功率下, 获得了3.2 W平均输出功率、9.7 ns脉冲宽度和52 kHz重复频率的激光输出, 经计算可知峰值功率达6.3 kW.

The output characteristics of a passively Q-switched Nd∶YAG/Cr4+∶YAG/YAG composite crystal laser at 1 064 nm was studied with diode-end-pumped system. The laser output characteristic parameters were compared among five output couplers with different transmittance, and between two Cr4+∶YAG crystals with initial transmittance of 84.1% and 90.6%. The experiment results show that the output parameters as average output power, pulse repetition frequency and pulse width could be optimized with transmittance of the output coupler. And the optimized transmittance also increased with the pump power. By the comparison of laser output characteristics between two crystals with different initial transmittance, the crystal having initial transmittance of 84.9% produced relatively low average power output, but its low pulse repetition frequency and narrow pulse width made the Q-switched laser peak power improved significantly. Under the incident pump power of 10.4 W, the maximum output power of 3.2 W was obtained using the output coupler with 30% transmittance. The calculated peak power was up to 6.3 kW as corresponding pulse width and pulse repetition frequency of 9.7 ns and 52 kHz, respectively.