Terahertz and third-harmonic generation by tightly focused bichromatic femtosecond pump pulses with comparable input intensities in air is studied both experimentally and theoretically. Plasma-assisted temporal shifts in the field of intense laser pulses are shown to lead to the time delay between the pump pulses in the vicinity of the focus. This delay can be compensated by the initial time delay that is evidenced by the measured as well as calculated correlation functions of the fundamental and second harmonics. The possibility to characterize the plasma channel length from the correlation function is discussed.

中文翻译：

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空气中双色飞秒激光脉冲的等离子体辅助时间偏移

在实验和理论上研究了紧紧聚焦的双色飞秒泵浦脉冲产生的太赫兹和三次谐波，它们在空气中的输入强度相当。在强激光脉冲场中，等离子体辅助的时间偏移显示为导致焦点附近泵浦脉冲之间的时间延迟。该延迟可以通过初始时间延迟来补偿，该初始时间延迟由基波和二次谐波的测量以及计算出的相关函数证明。讨论了根据相关函数表征等离子体通道长度的可能性。