Broadband Tuning of Optomechanical Cavities

TL;DR

This paper demonstrates broadband tuning of silicon nitride optomechanical microcavities over 32 nm using low power, leveraging large optomechanical coupling and low mechanical stiffness to achieve efficient resonance control.

Contribution

It introduces a method for broadband tuning of microcavity resonances via optomechanical coupling with low optical Q, enabling large displacement without regenerative oscillations.

Findings

Resonance tuning over 32 nm with 13 mW pump power.

Tuning power efficiency of 400 μW/nm.

Mechanical displacement up to 60 nm induced by optical forces.

Abstract

We demonstrate broadband tuning of an optomechanical microcavity optical resonance by exploring the large optomechanical coupling of a double-wheel microcavity and its uniquely low mechanical stiffness. Using a pump laser with only 13 mW at telecom wavelengths we show tuning of the silicon nitride microcavity resonances over 32 nm. This corresponds to a tuning power efficiency of only 400 $\mu$W/nm. By choosing a relatively low optical Q resonance ($\approx$18,000) we prevent the cavity from reaching the regime of regenerative optomechanical oscillations. The static mechanical displacement induced by optical gradient forces is estimated to be as large as 60 nm.