近日，哈尔滨工业大学的董全力及其研究小组与上海交通大学的张杰等人合作并取得一项新进展。经过不懈努力，他们发现与固体靶相互作用的少周期激光中纳米电子层传播产生的极紫外光和X射线。相关研究成果已于2024年4月18日在国际知名学术期刊《物理评论A》上发表。

该研究团队在短周期激光与固体密度等离子体相互作用中，提出了一种新的极紫外和X射线相干辐射产生机制。二维模拟结果表明，由相干尾迹辐射或相对论振荡镜像过程产生的高次谐波峰值与频率之间的关系并非遵循幂律或指数律。

在入射激光脉冲的有质动力和电荷分离电作用力的共同影响下，纳米电子层得以连续传播，并引发XUV和X射线的非线性散射。这些纳米电子层在激光场中运动时，由于激光磁场的变化，其特征电子方向发生了多次弯曲。

在每个弯曲点，即便归一化驱动激光振幅a₀仅为约1，这些电子仍能沿着偏离反射激光的方向发射强烈的同步辐射。通过对密度剖面截断和不截断两种情况下的模拟结果进行对比分析，研究人员发现这一机制的效率在很大程度上取决于预等离子体的特性。

附：英文原文

Title: Generation of extreme-ultraviolet and x-ray light from a propagating nanometer electron layer in few-cycle laser interaction with solid targets

Author: Xinmeng Liu, Dongning Yue, Quanli Dong, Ziqiang Shao, Zhe Li, Hao Teng, Zhiyi Wei, Feng Liu, Boyuan Li, Xiaohui Yuan, Min Chen, Zhengming Sheng, Jie Zhang

Issue&Volume: 2024/04/18

Abstract: A new generation mechanism of coherent extreme-ultraviolet (XUV) and x-ray radiation presents in the few-cycle laser interaction with solid density plasma. Two-dimensional simulations show that the XUV and x-rays intensities do not have power law or exponential law dependence on the frequency which is followed by the high harmonic spikes generated through the coherent-wake-emission or relativistically oscillating mirror processes. The XUV and x rays are actually nonlinearly scattered by the successively propagating nanometer electron layers formed in the combined effects of the ponderomotive forces of the incident laser pulse and the electric force due to the charge separation. The nanometer electron layers move in the laser field and the characteristic electrons have their directions bended several times due to the change of the laser's magnetic field. At every bending point, these electrons emit strong synchrotron radiation along a direction that deviates from the reflected laser, even if the normalized drive laser amplitude is at a₀≈1. The simulation results for two cases with and without the density profile truncation indicate that the efficiency of this mechanism strongly depends on the preplasma.

DOI: 10.1103/PhysRevA.109.043519

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.109.043519