等离子体削波纳秒激光脉冲波形测量

Temporal measurement of nanosecond laser pulse based on wave clipping of plasma

实验上采用比对方法测试了激光不经过固体与经过固体介质产生等离子体削波的脉冲波形信号,获得等离子体削波效应产生的脉冲削波倍数。实验结果表明,在波长1.064μm,脉宽1 ns,聚焦透镜焦距100 mm,薄石英片厚度100μm,约束等离子体的小孔直径80μm情况下,等离子体效应产生的脉冲削波倍数为12～14;分别改变石英片厚度和约束等离子体小孔直径,等离子体脉冲削波倍数不变;增加入射激光能量,脉冲削波倍数增加,且经过等离子体后的激光脉冲波形的后沿逐渐出现很陡的下降沿。在产生脉冲削波的截断点位置进行图形拼接重构得到激光脉冲波形信息。

The temporal profiles of two beams were obtained using comparison method,and then the energy reduction factor was acquired.The two beams—one passing through a transparent medium is clipped by laser-induced plasma,and the other transmits with a delay line— come into a set of photo-electricity conversion component and oscillographin simultaneously.It is shown that the transmitted pulse energy reduction factor is 12 to 14 with the 1.064 μm 1 ns laser pulse,a 100 mm focal length lens,a 100 μm thick fused silica plate,and a pinhole of 80 μm radius to ensure that the entire apertured area is from the plasma shuttered focal plane.Changing the thickness of the fused silica plate and the radius of the apertured pinhole respectively shows no impact on the energy reduction factor.The energy reduction factor increases while the energy of input beam enhances and the trailing edge of the clipped pulse gradually falls faster.The temporal profile of original laser pulse was reconstructed by profile stitching at the point of energy reduction.