In this paper, the generation of relativistic electron mirrors (REM) and the reflection of an ultra-short laser off the mirrors are discussed, applying two-dimension particle-in-cell simulations. REMs with ultra-high acceleration and expanding velocity can be produced from a solid nanofoil illuminated normally by an ultra-intense femtosecond laser pulse with a sharp rising edge. Chirped attosecond pulse can be produced through the reflection of a counter-propagating probe laser off the accelerating REM. In the electron moving frame, the plasma frequency of the REM keeps decreasing due to its rapid expansion. The laser frequency, on the contrary, keeps increasing due to the acceleration of REM and the relativistic Doppler shift from the lab frame to the electron moving frame. Within an ultra-short time interval, the two frequencies will be equal in the electron moving frame, which leads to the resonance between laser and REM. The reflected radiation near this interval and corresponding spectra will be amplified due to the resonance. Through adjusting the arriving time of the probe laser, a certain part of the reflected field could be selectively amplified or depressed, leading to the selective adjustment of the corresponding spectra.

中文翻译：

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相对论电子镜产生的啁啾阿秒脉冲的选择性放大

在本文中，应用二维细胞内粒子模拟，讨论了相对论电子镜 (REM) 的生成和超短激光从镜子的反射。具有超高加速度和膨胀速度的 REM 可以由具有锐利上升沿的超强飞秒激光脉冲正常照射的固体纳米箔产生。啁啾阿秒脉冲可以通过反向传播的探测激光从加速的 REM 反射产生。在电子运动坐标系中，REM 的等离子体频率由于其快速膨胀而不断降低。相反，由于 REM 的加速和从实验室坐标系到电子运动坐标系的相对论多普勒频移，激光频率不断增加。在极短的时间内，两个频率在电子运动坐标系中是相等的，这导致了激光和 REM 之间的共振。由于共振，该间隔附近的反射辐射和相应的光谱将被放大。通过调整探测激光的到达时间，可以选择性地放大或抑制某一部分的反射场，从而对相应的光谱进行选择性调整。