Externally Driven Nonlinear Time-Variant Metasurfaces

Abstract

Resonant photonic nanostructures exhibiting enhanced nonlinear response and efficient frequency conversion are an emergent platform in nonlinear optics. High-index semiconductor metasurfaces with rapidly tuned high-quality-factor (high-Q) resonances enable a novel class of time-variant metasurfaces, which expands the toolbox of color management at the nanoscale. Here, we report on the dynamic control of the nonlinear optical response in time-variant semiconductor metasurfaces supporting high-Q resonances in the near-infrared spectral range. Germanium metasurfaces reveal frequency conversion of the fundamental beam and blue-shift of 10 nm (3.05ω) and 40% broadening in the third-harmonic spectrum due to a subpicosecond-scale time-variant refractive index. A time-dependent coupled-mode theory, in qualitative agreement with the experimental data, validated the time-variant nature of the system. Our findings expand the scope of time-variant metasurfaces and may serve as base for the next generation of nanoscale pulse shapers, optical switches, and light sources.