Hybrid photonic/phononic crystals for vertically-integrated optomechanics

Thin dielectric membranes patterned with a sub-wavelength period structure can be designed to exhibit remarkable properties, including reflectivity in excess of 99.9%. When fabricated from silicon nitride, they can become superb mechanical resonators as well. In this work, we embed such photonic crystal reflectors in the bandgap of a phononic crystal, to attain ultrahigh mechanical quality factors. These hybrid devices can be incorporated into optical cavities and lasers, and offer unique new opportunities for optomechanical sensing and active-cavity optomechanics.