Electro-optic lithium niobate metasurfaces for tunable wavefront shaping

We demonstrate electrically tunable lithium niobate metasurfaces based on the electro-optic effect. Asymmetric one-dimensional lithium niobate gratings are designed to support quasi-bound states in the continuum with high quality factor. Thanks to the high spectral selectivity of the quasi-bound state, we can shift the resonant mode with a weak refractive index modulation that results from an applied voltage. At a fixed wavelength, this effect produces a phase shift that can be exploited to electrically address the metasurfaces and dynamically control its local phase response and wavefront.