Ponderomotive laser channelling and multi-channelling in homogeneous underdense plasma

TL;DR

This paper combines analytical theory and 3D PIC simulations to investigate laser pulse channeling in underdense plasma, demonstrating stable single channels, ring structures, and their stability properties under various conditions.

Contribution

It provides the first demonstration that a fully evacuated stationary channel can be achieved as an asymptotic state in PIC simulations, and explores the formation and stability of ring structures.

Findings

Single fully evacuated stationary channels are achievable in simulations.

Ring structures form enclosed by electron filaments but are unstable against azimuthal perturbations.

Higher densities lead to faster growth of ring instability.

Abstract

We have studied laser pulse channeling in underdense plasma by means of analytical theory and 3D PIC simulations. The most significant result of this paper is the demonstration of the single fully evacuated stationary channel solution can be reached an asymptotic state in PIC simulations. In the lower density and for a laser power above channeling power, we were able to reproduce in PIC simulations the analytical curve. We showed that single channels are stable structures against symmetric perturbations. We also studied the formation of the ring structure in theory and simulations. An evacuated ring enclosed by an electron filament was observed in our 3D simulations. However they always coexist with the main laser mode. The threshold power for ring structure formation is found. Our studies on stability of the rings against asymmetric perturbations show that ring structure is not stable against azimuthal perturbations. The growth rate of the instability is shorter for higher densities and it is therefore more effective at higher densities.