Inverse-designed release-free optomechanical crystal with high photon-phonon coupling

TL;DR

This paper presents a novel inverse-designed, release-free silicon optomechanical crystal with record-high photon-phonon coupling, enhancing thermal robustness and performance for quantum and classical applications.

Contribution

The authors develop and experimentally demonstrate a release-free silicon optomechanical crystal with record vacuum coupling rate using a new inverse-design algorithm.

Findings

Achieved a vacuum optomechanical coupling rate of about 800 kHz.

Demonstrated an optomechanical scattering rate nearly twice previous release-free devices.

Validated the effectiveness of the inverse-design framework for resonant optomechanical structures.

Abstract

Interactions between light and mechanics provide a powerful interface between optical and microwave-frequency signals, with applications spanning classical signal processing and quantum technologies. High-performance optomechanical devices require both strong photon-phonon coupling and tolerance to parasitic laser heating. Release-free optomechanical crystals provide improved thermal anchoring compared to suspended nanobeams, but have so far exhibited weaker vacuum optomechanical coupling rates, leaving a trade-off between coupling strength and thermal robustness. Here, we largely close this gap: we design and experimentally demonstrate a release-free silicon optomechanical crystal with a record vacuum optomechanical coupling rate of about $g_\text{OM} / (2 \pi) = 800$ kHz, comparable to suspended state-of-the-art devices. The resulting optomechanical scattering rate $\Gamma_\text{OM}/(2 \pi)= 1.1$ kHz is nearly twice that of previous release-free implementations. This performance is achieved by combining physics-guided human intuition with a multiphysics inverse-design algorithm introduced here for resonant optomechanical structures. Beyond the specific device demonstrated, the inverse-design framework is applicable to co-optimizing optical and mechanical resonances and eigenmodes more broadly. These results strengthen release-free optomechanical crystals as a platform for fast, low-noise classical and quantum optomechanics.