紫外超短脉冲激光放大过程中脉宽压缩的方案设计

Scheme design of pulse duration compression in amplification of untraviolet ultrashort pulse laser

采用放电泵浦KrF准分子激光放大器放大波长为248.4nm的紫外超短脉冲激光。对于能量为0.7mJ、脉宽为550fs的输入脉冲,在光束直径保持10mm不变的条件下,能量放大到15mJ,脉宽展宽到1200fs。为了压缩输出脉冲宽度,分析了群速度色散和自相位调制效应对脉宽展宽的影响。利用棱镜对,采用4种不同的实验方案对脉冲引入负的线性频率啁啾,以补偿KrF准分子激光放大器CaF2窗镜中的群速度色散和自相位调制对脉冲引入的正的线性频率啁啾。结果表明:在放大器之前放置棱镜对的方式可以在保持输出脉冲能量为15mJ的同时,在棱镜对间距为110cm的条件下,将输出脉冲宽度压缩到370fs,输出波长为248.4nm、带宽为0.4nm。

The discharge-pumped KrF excimer was used to amplify ultraviolet ultrashort pulse laser with wavelength of 248.4 nm.The laser energy was amplified from 0.7 mJ to 15 mJ,and the pulse duration was broadened from 550 fs to 1 200 fs, with the beam diameter of 10 mm unchanged. To compress the output pulse duration, the effects of group velocity dispersion and self phase modulation were analyzed,and experimental schemes with four different prism pair were used to introduce negative frequency chirp into the pulse laser in order to compensate the positive frequency chirp introduced by group velocity dispersion and self phase modulation in the CaF2 windows of the amplifer.The results show that if the prism pair is put before the amplifier, the pulse duration can be compressed to 370 fs when the length of the prism pair is 110 cm, while the output energy remains 15 mJ, the output wavelength is 248.4 nm,and the bandwidth is 0.4 nm.