Quasi-two-dimensional optomechanical crystals with a complete phononic bandgap

TL;DR

This paper demonstrates a fully planar silicon optomechanical crystal with a complete phononic bandgap, enabling control over GHz acoustic phonons for potential applications in quantum and classical information processing.

Contribution

It introduces a novel two-dimensional phononic crystal with a complete bandgap and integrates a nanoscale photonic cavity to probe localized acoustic modes.

Findings

Clear evidence of a complete phononic bandgap in the structure

Mechanical damping and mode density vary with geometry

Strong optomechanical coupling observed in localized modes

Abstract

A fully planar two-dimensional optomechanical crystal formed in a silicon microchip is used to create a structure devoid of phonons in the GHz frequency range. A nanoscale photonic crystal cavity is placed inside the phononic bandgap crystal in order to probe the properties of the localized acoustic modes. By studying the trends in mechanical damping, mode density, and optomechanical coupling strength of the acoustic resonances over an array of structures with varying geometric properties, clear evidence of a complete phononic bandgap is shown.