Externally driven nonlinear time-variant metasurfaces

TL;DR

This paper demonstrates dynamic control of nonlinear optical responses in semiconductor metasurfaces with high-Q resonances, enabling advanced nanoscale light manipulation such as frequency conversion and pulse shaping.

Contribution

It introduces a novel class of time-variant semiconductor metasurfaces with tunable high-Q resonances, validated by experiments and coupled-mode theory.

Findings

Observed frequency conversion and blue-shift in third harmonic signals

Achieved 40% broadening of the third harmonic signal

Validated time-variant behavior with coupled-mode theory

Abstract

Resonant photonic nanostructures exhibiting enhanced nonlinear responses and efficient frequency conversion are an emergent platform in nonlinear optics. High-index semiconductor metasurfaces with rapidly tuned 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-quality factor resonances in the near-infrared spectral range. Pump-probe measurements of germanium metasurfaces at negative pump-probe time delays reveals frequency conversion in the fundamental beam and a blue-shift of 10~nm (3.05$\omega$) and 40% broadening in the third harmonic signal due to the photoinduced time-variant refractive index. A time-dependent coupled-mode theory, in excellent 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.