High-Harmonic Generation and Correlated Electron Emission from Relativistic Plasma Mirrors at 1 kHz Repetition Rate

TL;DR

This paper demonstrates the first generation of extreme ultraviolet spectra from relativistic plasma mirror high-harmonic generation at a 1 kHz repetition rate, simultaneously producing energetic electrons, with spectra and electron distributions studied across various plasma density gradients and pulse durations.

Contribution

It reports the first observation of relativistic surface high-harmonic generation from plasma mirrors at high repetition rates, with detailed analysis of the effects of plasma density gradient and pulse parameters.

Findings

Relativistic high-harmonic spectra are generated at 1 kHz repetition rate.

Correlated electron emission occurs alongside high-harmonic generation.

Optimal plasma density gradient length is approximately one-tenth of the wavelength.

Abstract

We report evidence for the first generation of XUV spectra from relativistic surface high-harmonic generation (SHHG) on plasma mirrors at a kilohertz repetition rate, emitted simultaneously with energetic electrons. SHHG spectra and electron angular distributions are measured as a function of the experimentally controlled plasma density gradient scale length $L_\mathrm{g}$ for three increasingly short and intense driving pulses: 24~fs and $a_0=1.1$, 8~fs and $a_0=1.6$, and finally 4~fs and $a_0\approx2.1$, where $a_0$ is the peak vector potential normalized by $m_\mathrm{e} c/e$ with the elementary charge $e$, the electron rest mass $m_\mathrm{e}$, and the vacuum light velocity $c$. For all driver pulses, we observe correlated relativistic SHHG and electron emission in the range $L_\mathrm{g}\in[\lambda/25,\lambda/5]$, with an optimum gradient scale length of $L_\mathrm{g}\approx\lambda/10$.