Metasurface-stabilized optical microcavities

We demonstrate stable optical microcavities by counteracting the phase evolution of the cavity modes using an amorphous silicon metasurface as one of the two cavity end mirrors. Careful design allows us to limit the metasurface scattering losses at telecom wavelengths to less than 2% and using a distributed Bragg reflector as metasurface substrate ensures high reflectivity. Our first demonstration experimentally achieves telecom-wavelength microcavities with quality factors of up to 4600, spectral resonance linewidths below 0.4 nm, and mode volumes down to below 2.7$\lambda ^3$. We then show that the method introduces unprecedented freedom to stabilize modes with arbitrary transverse intensity profiles and design cavity-enhanced hologram modes. Our approach introduces the nanoscopic light control capabilities of dielectric metasurfaces to cavity electrodynamics and is directly industrially scalable using widespread semiconductor manufacturing processes.