Water-Based Coherent Detection of Broadband Terahertz Pulses
Water-Based Coherent Detection of Broadband Terahertz Pulses
复制标题
宽带太赫兹脉冲的水基相干检测
DOI：
10.1103/physrevlett.128.093902
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发表时间：
2022-03-04
影响因子：
8.6
通讯作者：
Liang-Liang Zhang
中科院分区：
文献类型：
--
作者：
Tan, Yong;Zhao, Hang;Liang-Liang Zhang
固体和气体已经被证明是太赫兹（THz）相干探测的材料。基于气体的相干检测方法需要高能量的探测激光束，并且在基于固体的方法中检测带宽是有限的。液体是否可以用于太赫兹探测并缓解这些问题还没有报道，这成为一个及时和有趣的话题，由于最近观察到的高效太赫兹波产生的液体。本文提出了一种基于液态水的太赫兹相干探测方案。当太赫兹脉冲和基波激光束在自由流动的水膜上混合时，随着等离子体的形成，产生二次谐波（SH）光束。将此太赫兹感应SH光束与控制SH光束相结合，我们成功地获得了频率范围为0.1-18 THz的太赫兹场的时间分辨波形。所需的探测激光能量低至几微焦耳。在可比的检测条件下，我们的方案的灵敏度是1个数量级高于空气为基础的方法。该方案对太赫兹波偏振和基波与控制SH光束之间的相位差敏感，为优化和偏振敏感探测提供了直接途径。能量标度和太赫兹诱导光束的偏振特性表明，它的产生可以归因于一个四波混频过程。这种产生机制使得探测激光、太赫兹感应SH和太赫兹场之间的关系简单，有利于检测装置的鲁棒性和灵活性。
Both solids and gases have been demonstrated as the materials for terahertz (THz) coherent detection. The gas-based coherent detection methods require a high-energy probe laser beam and the detection bandwidth is limited in the solid-based methods. Whether liquids can be used for THz detection and relax these problems has not yet been reported, which becomes a timely and interesting topic due to the recent observation of efficient THz wave generation in liquids. Here, we propose a THz coherent detection scheme based on liquid water. When a THz pulse and a fundamental laser beam are mixed on a free-flowing water film, a second harmonic (SH) beam is generated as the plasma is formed. Combining this THz-induced SH beam with a control SH beam, we successfully achieve the time-resolved waveform of the THz field with the frequency range of 0.1-18 THz. The required probe laser energy is as low as a few microjoules. The sensitivity of our scheme is 1 order of magnitude higher than that of the air-based method under comparable detection conditions. The scheme is sensitive to the THz polarization and the phase difference between the fundamental and control SH beams, which brings direct routes for optimization and polarization sensitive detection. Energy scaling and polarization properties of the THz-induced beam indicate that its generation can be attributed to a four-wave mixing process. This generation mechanism makes simple relationships among the probe laser, THz-induced SH, and THz field, favorable for robustness and flexibility of the detection device.