基频和三倍频Nd:YAG激光诱导熔石英损伤特性

 采用光电探测器和数字示波器检测散射光脉冲信号，研究了基频和三倍频Nd:YAG激光诱导熔石英损伤过程，给出了泵浦光和探针光的散射光光电信号；比较了基频和三倍频激光作用下熔石英烧蚀斑显微照片，并分析了其损伤机理。结果显示:在ns脉冲激光作用下，熔石英损伤均发生在泵浦激光脉冲峰值附近，且基频光作用下损伤开始时间点比三倍频作用下早；在多脉冲或高能量激光辐照下，检测到了等离子体闪光信号，等离子体闪光发生在时间延迟21 ns附近。基于Keldysh理论计算了基频光和三倍频光作用下，熔石英光致电离速率同激光强度的关系。

Damage induced 0n fused silica by fundamental frequency and third harmonic of Nd:YAG laser

The damage processes of fused silica under the fundamental frequency and third harmonic of Nd:YAG laser were studied with instantaneous scattering pulses measurements via fast photodiodes and high bandwidth oscilloscope. The optical micrographs of ablated craters on fused silica surface were also analyzed. The sharp increase of scattered light of pump pulse was assumed to be the damage precursor, therefore, the damage started nearly at the peak of the pump pulse. Fundamental frequency laser induced-damage of fused silica began before that of the third harmonic laser. The plasmas flash due to ion-electron recombination occurred about 21 ns after the peak of pump pulses. Based on Keldysh theory, the photoionization rate of fused silica vs laser intensity under 355 and 1 064 nm laser was calc