Electrooptic (EO) sampling is a method in THz time-domain spectroscopy. In previous studies, a thick EO crystal with a broadband probe pulse is used to meet the requirements of THz detection with a large time window and high-precision frequency spectrum. However, the broadband probe pulses are significantly broadened in the time domain during the transmission in thick EO crystals due to group velocity dispersion, which distorts the EO signal. In this article, a negative prechirp of broadband (10 fs in full-width at half-maximum) laser pulse is utilized to compensate the dispersion and enhances the detected signals. In the experiments, we use an interdigital photoconductive antenna to generate typical THz pulses in the region of 0.1-3 THz. The measurement results confirm that the prechirp of -2100 fs2 is more effective to optimize the detected signals in ZnTe crystal with a thickness of 3 mm and enhances the EO signal by 71%, and the frequency redshift caused by the filter effect of the electrooptical response function is decreased. Meanwhile, the experimental results show that the enhancements of different prechirps depend on the frequency components of THz pulses and the frequency-dependent optimization of EO sampling is effective, which is consistent with the simulation results. This technique is helpful to optimize the EO sampling in thick ZnTe crystals to obtain the large time window and higher signal-to-noise ratio of EO sampling.

中文翻译：

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厚 EO 晶体中啁啾宽带探测脉冲太赫兹脉冲电光采样的优化


电光（EO）采样是太赫兹时域光谱中的一种方法。在以往的研究中，采用带有宽带探测脉冲的厚EO晶体来满足大时间窗和高精度频谱的太赫兹探测要求。然而，由于群速度色散，宽带探测脉冲在厚电光晶体中传输期间在时域中显着展宽，从而使电光信号失真。在本文中，利用宽带（半高全宽为 10 fs）激光脉冲的负预线性调频来补偿色散并增强检测到的信号。在实验中，我们使用叉指光电导天线来产生0.1-3 THz范围内的典型太赫兹脉冲。测量结果证实-2100 fs2的预啁啾更有效地优化了厚度为3 mm的ZnTe晶体中的检测信号，使电光信号增强了71%，并且电光响应的滤波效应引起的频率红移功能下降。同时，实验结果表明，不同预线性调频的增强效果取决于太赫兹脉冲的频率分量，并且电光采样的频率相关优化是有效的，这与仿真结果一致。该技术有助于优化厚ZnTe晶体中的EO采样，以获得大时间窗和更高的EO采样信噪比。