Self-compression of high-intensity ferntosecond laser pulses in air

利用高重复频率(1kHz)、吉瓦级飞秒激光脉冲实验验证了高强度飞秒脉冲在空气中的自压缩现象，研究了入射脉冲在不同初始啁啾情况下经空气中聚焦成丝后，时域及频域特性随入射脉冲能量的变化规律．实验结果表明，在无需后继色散补偿情况下，高强度飞秒脉冲仅通过在空气中的非线性传输过程就可以实现脉冲压缩；在入射脉冲为负啁啾情况下，实验观察到脉冲光谱及时域宽度同时得到压缩，并可获得比激光源所能提供的更短的近双曲正割型变换限脉冲．Pulse self-compression in air is experimentally demonstrated by use of 1kHz femtosecond laser pulses with input power on the order of GW. Under the conditions of different initial chirps, the temporal and spectral characteristics of the output pulse after being focused in air are studied in detail as a function of input pulse energy. The experimental results show that, the temporal duration of high-intensity femtosecond laser pulses could be shortened solely through nonlinear propagation in air, without any additional dispersion compensation. Moreover, with the input pulse negatively chirped, we observed that the spectrum and pulse duration could be compressed simultaneously, and near sech(2) transform-limited output pulses shorter than original laser pulse source were obtained