展宽压缩器的谱透过率对短脉冲时间特性的影响

为了考察短脉冲激光装置中展宽压缩器的谱透过率对输出脉冲时间特性的影响,通过解析推导得到了激光脉冲通过平行光栅对的谱透过率表达式。结果表明:谱透过率不仅与光栅尺寸及光栅线密度有关,还与光束口径、入射角、光栅间距等参数有关;通常情况下展宽器的截止带通较小,对脉冲的信噪比有较大的影响;而压缩器中由于光束口径很大,有很宽的渐变透过率带通,对压缩后的脉宽及信噪比有利。目前常见的短脉冲激光系统中,限制输出脉冲信噪比的往往是展宽器而非压缩器。

Influence of spectrum transmissivity of grating-pair in stretcher and compressor on output pulse temporal properties

Analytic expressions of spectrum transmissivity for the parallel grating-pair is deduced, with which the influence of the stretcher and compressor on the temporal properties of the output pulse laser can be analyzed. The analysis results show that, the spectrum transmissivity depends not only on the size and groove density of the gratings, but also on the size of the incident beam, the incident angle and the distance between the gratings. In a short pulse laser system, the stretcher has a much smaller cut-off bandpass than the compressor, which will limit the enhancement of the temporal contrast of the output pulse.