Optical and mechanical design of a "zipper" photonic crystal optomechanical cavity

TL;DR

This paper presents the design of a nanoscale optomechanical cavity using photonic crystal concepts, achieving strong optical localization and high-quality factors for potential applications in sensing and quantum technologies.

Contribution

It introduces a novel design of a zipper photonic crystal optomechanical cavity with integrated optical and mechanical localization at the nanoscale, demonstrating high optical Q-factor and strong coupling.

Findings

Optical mode volume of 0.2 cubic wavelengths achieved.

Optical Q-factor of 7 million demonstrated.

Mechanical mode frequency around 170 MHz.

Abstract

Design of a doubly-clamped beam structure capable of localizing mechanical and optical energy at the nanoscale is presented. The optical design is based upon photonic crystal concepts in which patterning of a nanoscale-cross-section beam can result in strong optical localization to an effective optical mode volume of 0.2 cubic wavelengths ((\lambda_{c})^3). By placing two identical nanobeams within the near field of each other, strong optomechanical coupling can be realized for differential motion between the beams. Current designs for thin film silicon nitride beams at a wavelength of 1.5 microns indicate that such structures can simultaneously realize an optical Q-factor of 7x10^6, motional mass m~40 picograms, mechanical mode frequency ~170 MHz, and an optomechanical coupling factor (g_{OM}=d\omega_{c}/dx = \omega_{c}/L_{OM}) with effective length L_{OM} ~ \lambda = 1.5 microns.