Formal selection rules for Brillouin scattering in integrated waveguides and structured fibers

TL;DR

This paper develops a group-theoretical framework to determine the selection rules governing Stimulated Brillouin Scattering in structured waveguides, aiding device design and understanding of SBS physics.

Contribution

It introduces a formal, symmetry-based method to identify optical and acoustic mode interactions in structured waveguides for SBS.

Findings

Selection rules depend on waveguide symmetry.

Degeneracy of optical modes influences SBS interactions.

Framework applies to various symmetries like rectangular, triangular, hexagonal.

Abstract

We derive formal selection rules for Stimulated Brillouin Scattering (SBS) in structured waveguides. Using a group-theoretical approach, we show how the waveguide symmetry determines which optical and acoustic modes interact for both forward and backward SBS. We present a general framework for determining this interaction and give important examples for SBS in waveguides with rectangular, triangular and hexagonal symmetry. The important role played by degeneracy of the optical modes is illustrated. These selection rules are important for SBS-based device design and for a full understanding the physics of SBS in structured waveguides.