Guided acoustic and optical waves in silicon-on-insulator for Brillouin scattering and optomechanics

TL;DR

This paper demonstrates the simultaneous guiding of optical and acoustic waves in silicon-on-insulator structures, enabling efficient Brillouin scattering and optomechanical interactions with potential applications in integrated photonics.

Contribution

It introduces novel silicon waveguide designs that support both optical and acoustic modes with low losses and high Brillouin gain, advancing integrated optomechanics.

Findings

Thin waveguides exhibit gigahertz mechanical modes with phase velocities below the Rayleigh velocity.

Slot waveguides on glass achieve Brillouin gains of 500 and 50,000 1/(Wm) for backward and forward scattering.

Geometrically softened mechanical modes reduce acoustic radiation losses.

Abstract

We numerically study silicon waveguides on silica showing that it is possible to simultaneously guide optical and acoustic waves in the technologically important silicon on insulator (SOI) material system. Thin waveguides, or fins, exhibit geometrically softened mechanical modes at gigahertz frequencies with phase velocities below the Rayleigh velocity in glass, eliminating acoustic radiation losses. We propose slot waveguides on glass with telecom optical frequencies and strong radiation pressure forces resulting in Brillouin gains on the order of 500 and 50,000 1/(Wm) for backward and forward Brillouin scattering, respectively.