Mechanical-bound states in the continuum for photon trapping

Phonon trapping has an immense impact in many areas of science and technology. It usually relies on the mechanical suspension—an approach, while isolating selected vibrational modes, leads to serious drawbacks for interrogation of the trapped phonons, including limited heat capacity and excess noises via measurements. We introduce a novel paradigm of phonon trapping using mechanical bound states in the continuum (BICs) and its experimental realization. Coupling mechanical BICs with optical resonances leads to a new breed of optomechanical systems beyond suspended microcavities, which might mitigate measurement-induced parasitic heating and excess noises. We demonstrate a new breed of optomechanical crystals in two-dimensional slab-on-substrate structures empowered by mechanical BICs at 8 GHz and an optomechanical couplings up to 2.5 MHz per unit cell. We will further show work of merging mechanical BICs for suppression of scattering induced acoustic losses.