A numerical study of self-focusing and guiding of laser pulse of duration shorter than plasma wavelength

TL;DR

This study numerically investigates the self-focusing and guiding of ultra-short laser pulses in underdense plasma, revealing optimal conditions for stable propagation and effects of density ramps on laser guiding.

Contribution

It provides new insights into the stable propagation of ultra-short laser pulses in plasma and the influence of density ramps, with specific parameter optimization for laser guiding.

Findings

Stable propagation of laser pulses with L/λ_P~0.42 for a0~0.9.

Upward density ramps enhance self-focusing and guiding.

Density ramps reduce the minimum laser intensity needed for guiding.

Abstract

Self-focusing and guiding of ultra-short (pulse duration: L<lambda_P: plasma wavelength), intense laser pulses in underdense plasma relevant to laser wakefield electron acceleration has been studied numerically. The analysis considers contribution of wakefield non-linearities along with relativistic effects. Stable propagation of laser pulse with mild periodic oscillations upto few Rayleigh lengths were observed. Parametric optimization of the different laser and plasma parameters performed show that, laser pulse as short as L/lambda_P~0.42 is most stably guided upto few Rayleigh lengths for normalized laser intensity, a0~0.9. Next effect of upward density ramps were also studied and it was found that inclusion of an upward density ramp not only enhances self-focusing and guiding of the ultra-short laser pulse but also reduces required minimum laser intensity compared to uniform density profile.