Ionization waves of arbitrary velocity driven by a flying focus

TL;DR

This paper introduces a method to generate and control ionization waves with arbitrary velocities using a flying focus laser pulse, enabling new possibilities in laser-based plasma applications.

Contribution

It provides analytical models and simulations demonstrating how to manipulate the ionization front speed via a flying focus, advancing control over laser-induced plasma dynamics.

Findings

Ionization fronts can be driven at arbitrary velocities.

The intensity profile of flying focus pulses is self-similar.

Potential applications include improved Raman amplification and high harmonic generation.

Abstract

A chirped laser pulse focused by a chromatic lens exhibits a dynamic, or "flying," focus in which the trajectory of the peak intensity decouples from the group velocity. In a medium, the flying focus can trigger an ionization front that follows this trajectory. By adjusting the chirp, the ionization front can be made to travel at an arbitrary velocity along the optical axis. We present analytical calculations and simulations describing the propagation of the flying focus pulse, the self-similar form of its intensity profile, and ionization wave formation. The ability to control the speed of the ionization wave and, in conjunction, mitigate plasma refraction has the potential to advance several laser-based applications, including Raman amplification, photon acceleration, high harmonic generation, and THz generation.