Suppression of stimulated Raman scattering by angularly incoherent light, towards a laser system of incoherence in all dimensions of time, space, and angle

TL;DR

This paper demonstrates that angular incoherence in laser light significantly suppresses laser-plasma instabilities more effectively than temporal or spatial incoherence, offering a new approach for stable inertial confinement fusion.

Contribution

It provides the first analytical proof and 3D simulations showing angular incoherence's superior suppression of laser-plasma instabilities in ICF.

Findings

Angular incoherence reduces stimulated Raman scattering more than temporal or spatial incoherence.

Maximum field ratio drops from 0.2 to 0.05 with angular momentum spread.

Angular incoherence does not generate additional hot electrons.

Abstract

Laser-plasma instability (LPI) is one of the main obstacles in laser-driven inertial confinement fusion (ICF) for achieving predictable and reproducible fusion at high gain. For the first time we have proved analytically and confirmed with three-dimensional particle-in-cell simulations that angular incoherence has additional and much stronger suppression of the instability growth rate than the well-known temporal incoherence and spatial incoherence usually used in ICF studies. For the model used in our calculations, the maximum field ratio between the stimulated Raman scattering and the driving pulses drops from 0.2 for the Laguerre-Gaussian pulse with a single non-zero topological charge to 0.05 for the super light spring with an angular momentum spread and random relative phases. In particular, angular incoherence does not introduce extra undesirable hot electrons. This opens a novel way to suppress LPI with the light of an angular momentum spread and paves the way towards a low LPI laser system with a super light spring of incoherence in all dimensions of time, space, and angle.