Spatial, Spectral and Temporal Response of High Intensity Laser Plasma Mirrors- Direct Observation of the Ponderomotive Push

TL;DR

This study provides a comprehensive in situ analysis of plasma mirror surface dynamics under relativistic laser irradiation, revealing surface deformations and pulse modifications crucial for high-intensity laser applications.

Contribution

It introduces a multidimensional diagnostic approach to directly observe plasma surface evolution and pulse modifications during femtosecond laser interaction.

Findings

Surface deformations of a few hundred nanometers observed

Significant spectral and temporal modifications detected

Results align with 3D-PIC simulation predictions

Abstract

Plasma-based optics have emerged as a powerful platform for manipulating and amplifying ultra-intense laser pulses. However, the inherently nonlinear and dynamic nature of plasma leads to significant spatial, spectral, and temporal modulations when driven at relativistic intensities. These modifications can dramatically alter the structure of the reflected laser pulses, posing challenges for their use in applications such as vacuum ultraviolet (VUV) and X-ray generation, as well as relativistic particle acceleration. Comprehensive, multidimensional diagnostics are essential to accurately characterize these so-called `plasma mirrors' (PMs). We present a direct, \textit{in situ} measurement of the three-dimensional plasma surface evolution during femtosecond laser irradiation, achieved through simultaneous analysis of the wavefront, spectrum, and temporal profile of the reflected light. Our measurements reveal surface deformations on the order of a few hundred nanometers at relativistic intensities, in agreement with three-dimensional particle-in-cell (3D-PIC) simulations. Additionally, the PM induces substantial modifications to the pulse spectrum and temporal profile, introducing spatio-temporal couplings.