Design of tunable GHz-frequency optomechanical crystal resonators

TL;DR

This paper introduces a silicon optomechanical nanobeam resonator with a tunable 10.2 GHz acoustic mode, enabling frequency adjustments via an on-chip capacitor, which enhances the precision and scalability of optomechanical circuits.

Contribution

The work demonstrates a dynamically tunable GHz-frequency optomechanical resonator with significant frequency shift capability and high optical quality factors, advancing integrated optomechanical device design.

Findings

Achieved a 90 kHz/V^2 tuning of the acoustic mode frequency.

Optical Q factors up to 2.2 million were demonstrated.

Vacuum optomechanical coupling rate of 353 kHz was measured.

Abstract

We present a silicon optomechanical nanobeam design with a dynamically tunable acoustic mode at 10.2 GHz. The resonance frequency can be shifted by 90 kHz/V^2 with an on-chip capacitor that was optimized to exert forces up to 1 $\mu$N at 10 V operation voltage. Optical resonance frequencies around 190 THz with Q factors up to $2.2 \times 10^6$ place the structure in the well-resolved sideband regime with vacuum optomechanical coupling rates up to $g_0/2\pi = 353$ kHz. Tuning can be used, for instance, to overcome variation in the device-to-device acoustic resonance frequency due to fabrication errors, paving the way for optomechanical circuits consisting of arrays of optomechanical cavities.