Optomechanical cavities in silicon-on-insulator

Integrated optomechanical cavities allow precise control of optical and mechanical modes and enable strong photonphonon interactions in micron-scale volume, key for the implementation of microwave-photonic oscillators and quantum transducers. Silicon photonics provides low production cost and compatibility with the state-of-art optoelectronic circuitry. Thus, it is particularly interesting for the implementation of on-chip optomechanics. However, silicon has higher stiffness and acoustic velocity than the silica cladding, hampering phonon confinement in silicon-on-insulator (SOI) waveguides. Here, we present our most recent results on SOI optomechanical systems coupling mechanical and guided optical modes. The cavities use silicon pillars with subwavelength period. Strong radiation pressure is exploited to drive the optomechanical coupling. Based on this concept, we experimentally demonstrate the optomechanical coupling between photons and high-quality factor phonons in non-suspended cavities, with a great potential for applications in quantum and classical photonics.