Resonant metasurfaces: wavelength-selective wavefront shaping and nonlinear generation

Metasurfaces—structured planarized optical devices with a thickness thinner than or comparable to the wavelength of light—typically support a "local" response, i.e., they tailor the optical wavefront through the independent response of each meta-unit. In contrast, "nonlocal" metasurfaces are characterized by an optical response dominated by collective modes over many meta-units. In this talk, I will illustrate a rational design paradigm using quasi-bound states in the continuum to realize nonlocal metasurfaces. I will report experimental demonstration of a few device functionalities: (a) devices that produce narrowband spatially tailored wavefronts at multiple selected wavelengths and yet are otherwise transparent, (b) nonlocal metasurfaces based on CMOS-compatible dielectric materials with thermo-optically reconfigurable wavefronts, and (c) nonlinear resonant GaN metasurfaces growth by templated molecular beam epitaxy for efficient sum frequency generation.