Nonlocality Engineering in Optical Metasurfaces

In this talk, I will discuss our recent advances on metasurfaces that can efficiently manipulate the impinging wavefront based on highly delocalized modes, stemming from long-range resonant interactions and lattice phenomena. Different from conventional metasurface approaches, engineered nonlocality offers tailored spectral control, and at the same time can be tailored in space with large resolution using geometric phase concepts. Their response is ideal for wavefront shaping, imaging and signal processing applications, which may open new opportunities for wireless communication systems. We achieve their exotic features by combining quasi-bound states in the continuum with geometric phase variations in engineered metasurfaces, tailoring the supported eigenwaves in frequency, momentum, polarization, amplitude and phase. The resulting metasurfaces support responses selective to the impinging wave properties, effectively realizing ultrathin transparent films that highly reflect light only when illuminated by selected polarization, frequency and wavefront spatial distribution of choice. The demonstrated wavefront selectivity of these metasurfaces opens exciting opportunities for augmented reality, secure communications, emission management, modulators and enhanced wave-matter interactions. I will also discuss how their nonlocal features make them particularly relevant for reconfigurability.