Insight of breaking of powerful axisymmetrically-polarized laser pulses in under-dense plasma

TL;DR

This paper investigates how axisymmetrically-polarized laser pulses interact differently with under-dense plasma compared to Gaussian pulses, revealing unique spectral features and instabilities that affect electron acceleration.

Contribution

It provides experimental and simulation insights into the distinct behaviors and instabilities of axisymmetrically-polarized laser pulses in under-dense plasma.

Findings

Distinct spectral signatures observed experimentally.

Strong second harmonic emission near focus.

Reduced efficiency of electron acceleration with ALP.

Abstract

Interaction of axisymmetrically-polarized (radially or azimuthally-polarized), relativistically intense laser pulses (ALP) with under-dense plasma is shown experimentally to be different from the interaction of conventional Gaussian pulses. The difference is clearly observed in distinct spectra of scattered laser light as well as in appearance of a strong side emission of second harmonic in the vicinity of focus spot. According 3D particle-in-cell simulations, this is a result of instability in the propagation of ALP in under-dense plasma. Laser wakefield acceleration of electrons by ALP, therefore, is less efficient than that by Gaussian laser pulses but ALP may be interesting for efficient electron self-injection.