Circuit optomechanics: concepts and materials

Nanophotonic integrated circuits offer unique advantages for studying the interaction of light fields with mechanical structures. Because nanoscale waveguides are closely size-matched to nanomechanical devices, strong optomechanical interactions arise which can be harnessed in optical systems. The additional mechanical degrees of freedom provided by optomechanical devices are of particular interest for material systems in which tunability of the optical properties is not readily available. Here, suitable materials for the realization of chip-based optomechanical circuits are discussed and analyzed in terms of performance and the achievable quality factors. In particular, materials that offer large electronic band gaps are of interest, because in this case broadband optical transparency is achieved, combined with reduced free carrier effects. Several device geometries that can be used for enhancing optical forces are presented which address both an increase in the field gradient and the net optical force through resonant enhancement. Combining a variety of optomechanical components into full circuits thus provides a new route toward functional nanophotonic circuits with applications in sensing and optical signal processing in a chip-scale framework.