大能量窄脉宽风冷MOPA激光器研究

Research on high energy narrow pulse width air-cooled MOPA laser

研制了一种高功率激光二极管阵列(LDA)泵浦下的风冷大能量窄脉宽振荡放大(MOPA)激光器。振荡级采用端面泵浦Nd∶YAG晶体、退压式电光调Q的方式,在重复频率25 Hz时,获得了78 mJ单脉冲能量,脉冲宽度5.59 ns,光束质量因子M^(2)≈6.7。激光放大级采用侧面泵浦Nd∶YAG板条激光晶体双程放大的方式,在重复频率25 Hz时,获得了439 mJ单脉冲能量,脉冲宽度6.29 ns,峰值功率70.46 MW,光光转换效率为15.25%,光束质量因子M^(2)≈8.8,连续工作3 min,能量不稳定度小于5%。以脉冲串模式输出时,重复频率1 Hz,子脉冲数量10个,子脉冲间隔2 ms,脉冲包络能量为4.37 J。该激光器采用半导体热电制冷(TEC)配合强制风冷作为散热方式,省去了体积庞大的水冷系统,实现了高峰值功率Nd∶YAG激光器的小型化和无水冷化。

An air-cooled large energy narrow pulse width MOPA laser pump by a high power laser diode array(LDA)is developed.The end pump Nd∶YAG crystal and decompress electro-optical Q-switching method are used in the oscillation stage and at the repetition rate of 25 Hz,78 mJ single pulse energy,pulse width of 5.59 ns and beam quality factor of M^(2)≈6.7 are obtained.The laser amplifying stage adopts side-pump zig-zag slab Nd∶YAG crystal dual-pass amplification mode,and at the repetition frequency of 25 Hz,a single-pulse energy of 439 mJ with a pulse width of 6.29 ns and a peak power of 70.46 MW was obtained,with an optical conversion efficiency of 15.25%,a beam quality factor of M^(2)≈8.8,and a continuous operation of 3 min with an energy instability of less than 5%.When output in burst mode,the repetition rate is 1 Hz,the number of sub-pulses is 10,the interval of pulses of 2 ms,and the pulse envelope energy of 4.37 J.The laser adopts semiconductor thermoelectric refrigeration(TEC)combined with forced air cool as the heat dissipation mode,eliminating the bulky water cooling system and realizing the miniaturization of high peak power Nd∶YAG lasers and no water cooling.