Monolithic Cavity for Optomechanics Featuring a Bound State in the Continuum

Due to their low mass and high reflectivity, photonic-crystal membranes are excellent candidates for vibrating end mirrors in optomechanical cavities. Cavities with photonic-crystal membranes can support a quasi-bound state in the continuum (BIC), i.e., a resonance exhibiting an optical quality factor only limited by dissipative loss. Such cavities promise to access new regimes in optomechanics [1], e.g., the single-photon strong-coupling regime for applications in precision sensing [2] and quantum information processing [3]. However, previously proposed designs turned out to be difficult to fabricate with state-of-the-art nanolithography techniques. Furthermore, it is difficult to find new nanophotonic structures with a bound state in the continuum, in particular if a substrate breaks the mirror symmetry of the cavity.