Van der Waals active metasurfaces and heterostructures for phase modulation and polarization conversion

Abstract

The rapid advance in understanding of exciton resonances in layered van der Waals materials has now stimulated thinking about active metasurfaces that exploit excitonic modulation phenomena to enable ‘van der Waals active metasurfaces’. As one example, I will describe recent advances in electrically reconfigurable polarization conversion across the telecommunication wavelength range in tri-layer black phosphorus, enabling spectrally broadband polarization conversion over nearly half the Poincaré sphere. We also observe both linear to circular and cross-polarization conversion with voltage, demonstrating dynamic access to polarization diversity. As a second example, we discuss the observed large gate tunability of the complex refractive index and phase in monolayer MoSe₂ by Fermi level modulation near the A and B excitonic resonances for temperatures between 4 K to 150K. I will also give a general outlook for the wide range of possibilities for active van der Waals metasurfaces.