Novel Optomechanical Coupling Mechanisms in nanostructured Metasurfaces

Nanostructured metasurfaces with mechanical degrees of freedom provide a highly flexible and tunable platform for optomechanical systems. Bilayer metasurfaces with a high contrast grating as the top layer feature a high reflectivity due to the presence of bound states in the continuum (BIC). Simultaneously they can have a high mechanical susceptibility because of a flexible bottom layer, thus, providing strong optomechanical coupling that directly affects the optical properties of the metasurface.

In this work we investigate bilayer metasurfaces as a platform for dispersive and dissipative coupling in the frame of cavity optomechanics. By harnessing the presence of high-Q optical BIC modes we can theoretically achieve a single photon coupling of up to 1.3x10⁷ 1/s at mechanical frequencies of 15.5 MHz, thus approaching the regime of equal single photon coupling and mechanical resonance frequency. We present our first experimental work in which we characterise the optical properties of the bilayer metasurface and its underlying optical band structure. Furthermore, we examine the synchronisation of the independent mechanical micro oscillators mediated by the substrate and optical forces in the frame of an effective Kuramoto model.