纳秒至微秒可调脉宽输出CO<sub>2</sub>激光器

Abstract

研制了一台激光脉宽可变、输出波长可调谐的重复频率脉冲CO2激光器，并重点从理论和试验两个方面研究了Ge晶体声光调制时腔内光子数的时间变化过程。实验结果显示，在激光谐振腔内应用时，声光调制器理论并不适合解释激光器输出脉冲的时间行为，而必须由腔内Q开关速率方程所描述，分析其原因在于谐振腔内激光能级粒子数反转跃迁产生的开关增益效应远远大于声光晶体渡越时间的影响。对于Ge声光调制器施加射频控制信号时，激光器可以实现从ns至s范围的脉冲激光输出：平均功率3~8 W左右，重复频率为1 Hz~100 kHz范围，脉冲功率最高达到10 kW量级。使用金属衍射光栅替代输出耦合镜时，可以实现9.2~10.8 m范围三十余条谱线的可调谐输出。 A repetitive pulsed CO2 laser with variable pulse widths and tunable wavelengths was developed and the photon number change behavior inside the resonant cavity which has an inserted Ge crys- tal acousto-optical modulation was researched on both theory and experiment. The experimental results show that acousto-optical modulation theory is not suit to explain output characteristic of the laser pulses, the felicitous description should make use of the Q switched rate equation instead of, due to the reason that the action of switched gain effect produced from laser level population inversion transition is much larger than that of the transit-time along the acousto-optical crystal. When the Ge crystal is added with controlled radio frequency modulation signals, the laser can realize laser pulses with a range from nanosecond to microsecond under the conditions of 3 - 8 W average power and 1 Hz - 100 kHz repetition rate, corresponding the maximumpulse power 10 kW. Over 30 laser spectral lines between 9.2 - 10.8 m can be achieved if the metal grating is used for substituting the cavity output coupler.