Nie Zan, Pai Chih-Hao, Zhang Jie, Ning Xiaonan, Hua Jianfei, He Yunxiao, Wu Yipeng, Su Qianqian, Liu Shuang, Ma Yue, Cheng Zhi, Lu Wei, Chu Hsu-Hsin, Wang Jyhpyng, Zhang Chaojie, Mori Warren B, Joshi Chan
Key Laboratory of Particle and Radiation Imaging of Ministry of Education, Department of Engineering Physics, Tsinghua University, Beijing, 100084, China.
University of California Los Angeles, Los Angeles, CA, 90095, USA.
Nat Commun. 2020 Jun 3;11(1):2787. doi: 10.1038/s41467-020-16541-w.
Availability of relativistically intense, single-cycle, tunable infrared sources will open up new areas of relativistic nonlinear optics of plasmas, impulse IR spectroscopy and pump-probe experiments in the molecular fingerprint region. However, generation of such pulses is still a challenge by current methods. Recently, it has been proposed that time dependent refractive index associated with laser-produced nonlinear wakes in a suitably designed plasma density structure rapidly frequency down-converts photons. The longest wavelength photons slip backwards relative to the evolving laser pulse to form a single-cycle pulse within the nearly evacuated wake cavity. This process is called photon deceleration. Here, we demonstrate this scheme for generating high-power (~100 GW), near single-cycle, wavelength tunable (3-20 µm), infrared pulses using an 810 nm drive laser by tuning the density profile of the plasma. We also demonstrate that these pulses can be used to in-situ probe the transient and nonlinear wakes themselves.
相对论性强、单周期、可调谐红外光源的出现将开辟等离子体相对论非线性光学、脉冲红外光谱学以及分子指纹区域泵浦 - 探测实验等新领域。然而，用目前的方法产生这样的脉冲仍然是一个挑战。最近，有人提出，在适当设计的等离子体密度结构中，与激光产生的非线性尾波相关的随时间变化的折射率会使光子迅速进行频率下转换。波长最长的光子相对于不断演化的激光脉冲向后滑动，在几乎排空的尾波腔体内形成单周期脉冲。这个过程被称为光子减速。在这里，我们通过调整等离子体的密度分布，展示了使用810纳米驱动激光产生高功率（约100吉瓦）、近单周期、波长可调谐（3 - 20微米）红外脉冲的方案。我们还证明了这些脉冲可用于原位探测瞬态和非线性尾波本身。
