Non-adiabatic metasurfaces as a platform for time-varying photonics

Time-varying media emerged as an exciting platform for novel effects in photonics, including ultra-efficient frequency mixing, non-reciprocity, and light-matter interactions beyond the time-bandwidth limit. Here, we discuss semiconductor metasurfaces—quasi-planar periodic arrays of resonant semiconductor nanoparticles—as time-varying photonic devices. Femtosecond optical pumping in a non-adiabatic regime results in broadband frequency translation, gain, and a dynamically growing quality factor (Q-boosting) that enhances nonlinear and quantum optical phenomena. We conclude with an outlook with non-adiabatic metasurfaces serving as a platform for squeezed state generation, frequency-division multiplexing, and frequency-domain quantum information.