Resonance absorption of a broadband laser pulse

TL;DR

This paper investigates how broadband infrared laser pulses influence resonance absorption in inertial confinement fusion, revealing that bandwidth suppresses nonlinear absorption effects but cannot eliminate linear resonance absorption.

Contribution

The study provides new simulation insights into the impact of laser bandwidth on resonance absorption, highlighting limitations in reducing absorption in ICF.

Findings

Bandwidth has little effect on resonance absorption in the linear regime.

Bandwidth suppresses nonlinear resonance absorption caused by electromagnetic decay instability.

Linear resonance absorption persists regardless of bandwidth.

Abstract

Broad bandwidth, infrared light sources have the potential to revolutionize inertial confinement fusion (ICF) by suppressing laser-plasma instabilities. There is, however, a tradeoff: The broad bandwidth precludes high efficiency conversion to the ultraviolet, where laser-plasma interactions are weaker. Operation in the infrared could intensify the role of resonance absorption, an effect long suspected to be the shortcoming of early ICF experiments. Here we present simulations exploring the effect of bandwidth on resonance absorption. In the linear regime, bandwidth has little effect on resonance absorption; in the nonlinear regime, bandwidth suppresses enhanced absorption resulting from the electromagnetic decay instability. These findings evince that regardless of bandwidth, an ICF implosion will confront at least linear levels of resonance absorption.