Optomechanical and Photothermal Interactions in Suspended Photonic Crystal Membranes

TL;DR

This paper introduces a novel suspended silicon photonic-crystal membrane system with strong optomechanical interactions, enabling advanced sensing and mechanical control through optomechanical and photothermal effects.

Contribution

The work demonstrates the fabrication of a stress-managed, ultrathin silicon membrane with the strongest optomechanical coupling reported, and explores its dynamic interactions for sensing applications.

Findings

Achieved a tunable gap below 200 nm between membrane and substrate.

Measured the strongest repulsive optomechanical coupling to date (~ -65 GHz/nm).

Demonstrated cooling and amplification of mechanical modes via photothermal effects.

Abstract

We present here an optomechanical system fabricated with novel stress management techniques that allow us to suspend an ultrathin defect-free silicon photonic-crystal membrane above a Silicon-on-Insulator (SOI) substrate with a gap that is tunable to below 200 nm. Our devices are able to generate strong attractive and repulsive optical forces over a large surface area with simple in- and outcoupling and feature the strongest repulsive optomechanical coupling in any geometry to date (gOM/2{\pi} ~ -65 GHz/nm). The interplay between the optomechanical and photo-thermal-mechanical dynamics is explored, and the latter is used to achieve cooling and amplification of the mechanical mode, demonstrating that our platform is well-suited for applications in low-power mass, force, and refractive index sensing as well as and optomechanical accelerometry.