Phase-locking in cascaded stimulated Brillouin scattering

TL;DR

This paper investigates the phase-locking mechanisms in Brillouin frequency combs generated through cascaded stimulated Brillouin scattering, analyzing nonlinear interactions including Kerr effects and acoustic coupling to understand stable spectral phase formation.

Contribution

It derives comprehensive coupled-mode equations incorporating all relevant nonlinear interactions, revealing different phase-locking regimes based on spatial variation scales.

Findings

Identification of regimes with stable phase-locking

Analysis of Kerr and acoustic nonlinear contributions

Derivation of coupled-mode equations including all interactions

Abstract

Cascaded stimulated Brillouin scattering (SBS) is a complex nonlinear optical process that results in the generation of several optical waves that are frequency shifted by an acoustic resonance frequency. Four-wave mixing (FWM) between these Brillouin shifted optical waves can create an equally spaced optical frequency comb with a stable spectral phase, i.e. a Brillouin frequency comb (BFC). Here, we investigate phase-locking of the spectral components of BFCs, considering FWM interactions arising from the Kerr-nonlinearity as well as from coupling by the acoustic field. Deriving for the first time the coupled-mode equations that include all relevant nonlinear interactions, we examine the contribution of the various nonlinear processes to phase-locking, and show that different regimes can be obtained that depend on the length scale on which the field amplitudes vary.