  Whispering gallery mode (WGM) optomechanical resonators are a promising
technology for the simultaneous control and measurement of optical and
mechanical degrees of freedom at the nanoscale. They offer potential for use
across a wide range of applications such as sensors and quantum transducers.
Double-disk WGM resonators, which host strongly interacting mechanical and
optical modes co-localized around their circumference, are particularly
attractive due to their high optomechanical coupling. Large-scale integrated
fabrication of silicon double-disk WGM resonators has not previously been
demonstrated. In this work we present a process for the fabrication of
double-layer silicon-on-insulator wafers, which we then use to fabricate
functional optomechanical double silicon disk resonators with on-chip optical
coupling. The integrated devices present an experimentally observed optical
quality factors of the order of 10^5 and a single-photon optomechanical
coupling of approximately 15 kHz.
