利用块状介质进行飞秒强激光脉冲的腔外压缩

Extracavity Femtosecond High Intensity Laser Pulse Compression by Bulk Media

高强度飞秒激光脉冲的腔外压缩是获得高次谐波阿秒脉冲驱动源的必要手段。实验研究了超强超短飞秒激光脉冲在经过块状介质后的光谱展宽和色散补偿压缩现象。单脉冲能量0.26 mJ,脉宽50 fs的激光脉冲经透镜在空气中聚焦后再入射到块状材料上,出射脉冲光谱被展宽到接近40 nm。由于在块状材料中的自聚焦效应,出射光束质量变好并保持较小的空间啁啾。利用熔融石英棱镜对补偿带有正色散的出射脉冲,最后得到>0.1 mJ,19 fs的压缩脉冲。利用SPIDER装置测量了出射脉冲的脉宽和光谱相位。整个系统的能量效率大约为35%,压缩后的激光脉冲具有很好的空间分布和平滑的时域包络。实验结果实现了利用块状材料对飞秒激光脉冲的腔外压缩,这种方法将适用于对更高能量飞秒脉冲的压缩。

Extracavity femtosecond laser pulse compression is an indispensable method to obtain the driver for attosecond extreme ultraviolet （XUV） pulse by high harmonic generation. The pulse spectrum broadening and dispersion compensation compression phenomenon when focusing the laser pulse into bulk media are experimentally investigated. The 0.26 mJ, 50 fs laser pulse is focused into the bulk media, and the output spectrum width is broadened to nearly 40 nm. The beam maintains good quality and the spatial chirp of the laser beam is low because of the self-focusing phenomenon during the transmission in the bulk media. After compensating the positive chirp by the fussed silica prism pair, the pulse duration is compressed to 19 fs and the pulse energy is 〉0. 1mJ with an efficiency of 35%. The pulse duration and the spectral phase are measured by SPIDER. The compressed laser pulse has quite good spatial profile and high contrast. The extracavity compression of high intensity femtosecond laser pulses has been carried out by use of bulk media, this method will be useful in the compression experiment on higher energy femtosecond laser pulse.