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

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 and correlated to the emission of energetic electrons. We present measurements of SHHG spectra and electron angular distributions as a function of the experimentally controlled plasma density gradient scale length L for three increasingly short and intense driving pulses: 24 fs (9 optical cycles) and a0 = 1.1, 9 fs (3.5 optical cycles) and a0 = 1.8, and finally 4 fs (1.7 optical cycles) and a0 ≈ 2.0. For all driver pulses, we observe relativistic SHHG in the range L ∈ [λ/25, λ/10], with an optimum gradient scale length of L ≈ λ/15.

Quantum-Optical Spectrometry in Relativistic Laser–Plasma Interactions Using the High-Harmonic Generation Process: A Proposal

“…The plasma density scale length L was controlled by setting a delay of ≈ 2 ps between the pre-and the main pulse. This results to an L ≈ λ/20 (measured by mean spatial-domain interferometry [51]) which optimizes the conditions for RHH harmonic emission [45,46]. In Figure 3b we show a representative RHH spectrum generated by this source using a sinusoidal (CEP = π/2) ≈ 3.6 fs driving field.…”

“…Firstly, in order to achieve high intensity in the interaction region, a prerequisite for RHH, a tight focusing condition is necessary. Furthermore, the RHH generation efficiency is optimized by tuning the plasma density gradient [45,46]. These two criteria together, increase the resulting high harmonic beam divergence making the beam collection and manipulation an issue to be addressed.…”