Optoacoustic solitons in Bragg gratings

TL;DR

This paper introduces a new class of gap-acoustic solitons in Bragg gratings, which couple optical and acoustic waves, providing exact solutions and insights into their stability and dynamics.

Contribution

The study derives exact analytic solutions for gap-acoustic solitons, revealing their structure, stability properties, and the influence of acoustic coupling on their behavior.

Findings

Exact solutions for gap-acoustic solitons are obtained.

Coupling to acoustic waves stabilizes certain oscillatory instabilities.

Supersonic solitons exhibit a unique instability leading to deceleration and direction change.

Abstract

Optical gap solitons, which exist due to a balance of nonlinearity and dispersion due to a Bragg grating, can couple to acoustic waves through electrostriction. This gives rise to a new species of ``gap-acoustic'' solitons (GASs), for which we find exact analytic solutions. The GAS consists of an optical pulse similar to the optical gap soliton, dressed by an accompanying phonon pulse. Close to the speed of sound, the phonon component is large. In subsonic (supersonic) solitons, the phonon pulse is a positive (negative) density variation. Coupling to the acoustic field damps the solitons' oscillatory instability, and gives rise to a distinct instability for supersonic solitons, which may make the GAS decelerate and change direction, ultimately making the soliton subsonic.