Active and dynamically tunable semiconductor resonators and metasurfaces

We present our latest progress in the study of different tunable and active mechanisms in various materials that exhibit large modulation of optical constants and are used to implement active resonators and metasurfaces. We first discuss tuning of infrared Mie-resonant Si and Ge metasurfaces by modulating their free carrier density. We then move to discuss thermo-optic (TO) effects in Si, Ge and InSb and demonstrate tuning of Mie resonances by more than the resonance linewidth. Exploiting the peak TO coefficient of Si near its bandgap, we realize reconfigurable metasurfaces and tunable metafilters. We also show that phase transition materials such as VO2 can be used to implement active devices. We demonstrate electrically tunable Ge on VO2 resonators acting both as amplitude and phase modulators. Finally, we demonstrate ultra-wide dynamic tuning of PbTe meta-atoms. Taking advantage of the anomalously large TO coefficient and high refractive index of PbTe, we demonstrate high-quality factor resonances that are tuned by several linewidths with temperature modulation as small as ΔT~10K. We reveal that the origin for this exceptional tunability is due to an increased TO coefficient of PbTe at low temperatures. When combined into metasurface arrays these effects can be exploited in ultra-narrow active notch filers and metasurface phase shifters that require only few-kelvin modulation. We also study photoluminescence properties of lead chalcogenides from single antenna resonators and metasurface arrays towards the implementation of infrared emitting metasurfaces.