Active nonlocal metasurfaces

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 refractiveindex tuning and mechanical stretching. We experimentally demonstrate proof-of-principle thermo-optically tuned nonlocal metasurfaces made of silicon and numerically demonstrate nonlocal metasurfaces that thermooptically 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.

Automated summary

Optical metasurfaces for wavefront shaping face challenges in actively tuning and reconfiguring wavefronts, with nonlocal metasurfaces functioning based on modes supported by adjacent meta-units. These nonlocal metasurfaces can produce sharp spectral features but typically lack spatial control of the outgoing wavefront. Leveraging enhanced light-matter interactions associated with sharp Fano resonances, active modulation of optical spectra and wavefronts can be explored without the need for unusual materials and fabrication or active control of individual meta-units.