Modeling ultrafast shadowgraphy in laser-plasma interaction experiments

TL;DR

This paper models ultrafast shadowgraphy in laser-plasma experiments using 3D simulations and Fourier optics to interpret experimental images and recover dynamic plasma information from single shots.

Contribution

It introduces a comprehensive simulation framework for ultrafast shadowgraphy, linking synthetic and experimental images and enabling time-resolved plasma diagnostics.

Findings

Synthetic shadowgrams match experimental data when considering imaging setup effects.

Parameter variations significantly influence shadowgram features.

Broadband, chirped probes can extract time-dependent plasma information from single shots.

Abstract

Ultrafast shadowgraphy is a new experimental technique that uses few cycle laser pulses to image density gradients in a rapidly evolving plasma. It enables structures that move at speeds close to the speed of light, such as laser driven wakes, to be visualized. Here we study the process of shadowgraphic image formation during the propagation of a few cycle probe pulse transversely through a laser-driven wake using three-dimensional particle-in-cell simulations. In order to construct synthetic shadowgrams a near-field snapshot of the ultrashort probe pulse is analyzed by means of Fourier optics, taking into account the effect of a typical imaging setup. By comparing synthetic and experimental shadowgrams we show that the generation of synthetic data is crucial for the correct interpretation of experiments. Moreover, we study the dependence of synthetic shadowgrams on various parameters such as the imaging system aperture, the position of the object plane and the probe pulse delay, duration and wavelength. Finally, we show that time-dependent information from the interaction can be recovered from a single shot by using a broadband, chirped probe pulse and subsequent spectral filtering.