Active nonlocal metasurfaces

Abstract

Abstract Actively tunable and reconfigurable wavefront shaping by optical metasurfaces poses a significant technical challenge often requiring unconventional materials engineering and nanofabrication. Most wavefront‐shaping metasurfaces can be considered “local” in that their operation depends on the responses of individual meta‐units. In contrast, “nonlocal” metasurfaces function based on the modes supported by many adjacent meta‐units, resulting in sharp spectral features but typically no spatial control of the outgoing wavefront. Recently, nonlocal metasurfaces based on quasi‐bound states in the continuum have been shown to produce designer wavefronts only across the narrow bandwidth of the supported Fano resonance. Here, we leverage the enhanced light‐matter interactions associated with sharp Fano resonances to explore the active modulation of optical spectra and wavefronts by refractive‐index tuning and mechanical stretching. We experimentally demonstrate proof‐of‐principle thermo‐optically tuned nonlocal metasurfaces made of silicon and numerically demonstrate nonlocal metasurfaces that thermo‐optically switch between distinct wavefront shapes. This meta‐optics platform for thermally reconfigurable wavefront shaping requires neither unusual materials and fabrication nor active control of individual meta‐units.

Topics & Concepts