Spatio-temporal control of THz emission
Spatio-temporal control of THz emission
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DOI：
10.1038/s42005-022-00914-2
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发表时间：
2022-05-31
影响因子：
5.5
通讯作者：
Hatanaka, Koji
中科院分区：
文献类型：
--
作者：
Huang, Hsin-hui;Juodkazis, Saulius;Hatanaka, Koji
强太赫兹源有望为非线性太赫兹科学技术的进一步发展提供动力。像水这样的液体在强激光照射下具有耐用性和连续可重复使用的特性，但目前对水靶太赫兹辐射的研究还很有限。通过时空偏移照射两个交叉线偏振飞秒激光脉冲（800nm, 35fs，变换限制），证明了在倾斜的微细水流中太赫兹发射的极化精细控制。在8 μ m焦斑之间的优化水平偏移量为11 μ m，延迟时间为4.7ns时，获得圆极化太赫兹辐射，其强度比单脉冲辐照增强1500倍以上。结果表明，优化双脉冲辐照后，从激光到太赫兹的光子数效率达到7.1 x 10（-3）。偏振分辨太赫兹时域光谱和时间分辨阴影成像结果表明，圆偏振太赫兹辐射来源于水流前方的焦体。由于空气击穿和水烧蚀介导的质量输运引起的预脉冲与沿主脉冲光路的激光尾迹场之间的耦合是造成点状单周期太赫兹辐射的原因。流动液体的强辐照是产生太赫兹辐射的一种精细控制手段。本文演示了一种双脉冲太赫兹产生方案，该方案依赖于预脉冲的空间和时间偏移来控制极化和发射强度。
Intense THz sources are expected for further progresses in nonlinear THz science and technology. Liquids like water are durable and continuously-reusable under intense laser irradiation for THz emission though such studies on THz emission from water targets are so far limited. Polarisation fine control of THz emission is demonstrated with a tilted micro-thin water flow by the irradiation of two cross-linearly-polarised femtosecond laser pulses (800nm, 35fs, transform-limited) with spatio-temporal offsets. With an optimized horizontal offset at similar to 11 mu m between the similar to 8 mu m focal spots and time delay at 4.7ns, circularly-polarised THz emission is obtained with its intensity enhancement more than 1,500-times if compared with the single pulse irradiation. It is shown that the photon-number-based efficiency from the laser to THz at 7.1 x 10(-3) is achieved with the optimisation of the double pulse irradiation. Polarisation-resolved THz time-domain spectroscopy and time-resolved shadowgraphy imaging reveal that the circularly-polarised THz emission originates from the focal volume in front of the water flow. Coupling between a shockwave due to air-breakdown and water ablation-mediated mass transport by the pre-pulse with a laser wake-field along the optical path of the main pulse is responsible for the point-like single-cycle THz emission.Intense irradiation of flowing liquid has emerged as a means of generating THz emission with fine control. Here, a double-pulse THz generation scheme is demonstrated that relies on spatial and temporal off-sets of a pre-pulse to control both polarization and emission intensity.