Nonlinear Frequency Shift in Raman Backscattering and its Implications for Plasma Diagnostics

TL;DR

This paper investigates the nonlinear frequency shift in Raman backscattering of intense laser pulses in plasma, revealing an intensity and density dependent shift that offers a new diagnostic tool for laser-plasma interactions.

Contribution

It presents a weakly nonlinear dispersion relation predicting a novel frequency shift, validated against experimental data, enhancing plasma diagnostic techniques.

Findings

Frequency shift depends on laser intensity and plasma density.

The shift is opposite to simple relativistic predictions.

Experimental results confirm the theoretical model.

Abstract

Raman backscattered radiation of intense laser pulses in plasma is investigated for a wide range of intensities relevant to laser wakefield acceleration. The weakly nonlinear dispersion relation for Raman backscattering predicts an intensity and density dependent frequency shift that is opposite to that suggested by a simple relativistic consideration. This observation has been benchmarked against experimental results, providing a novel diagnostic for laser-plasma interactions.