Excitonic beam steering in an active van der Waals metasurface

TL;DR

This paper demonstrates dynamic beam steering using an active van der Waals metasurface based on monolayer MoSe2, exploiting tunable excitonic resonances to control light reflection angles between -30° and 30°.

Contribution

It introduces a novel excitonic phased array metasurface that dynamically controls reflection phase and amplitude through excitonic resonance tuning, without relying on geometric nanostructuring.

Findings

Achieved beam steering angles from -30° to 30° at three excitonic wavelengths.

Controlled reflection amplitude and phase by tuning excitonic radiative and nonradiative rates.

Utilized monolayer MoSe2's excitonic resonances for wavefront shaping without geometric patterning.

Abstract

Two-dimensional transition metal dichalcogenides (2D TMDCs) are promising candidates for ultra-thin active nanophotonic elements due to the strong tunable excitonic resonances that dominate their optical response. Here we demonstrate dynamic beam steering by an active van der Waals metasurface that leverages large complex refractive index tunability near excitonic resonances in monolayer molybdenum diselenide (MoSe2). Through varying the radiative and nonradiative rates of the excitons, we can dynamically control both the reflection amplitude and phase profiles, resulting in an excitonic phased array metasurface. Our experiments show reflected light steering to angles between -30{\deg} to 30{\deg} at three different resonant wavelengths corresponding to the A exciton, B exciton, and trion. This active van der Waals metasurface relies solely on the excitonic resonances of the monolayer MoSe2 material rather than geometric resonances of patterned nanostructures, suggesting the potential to harness the tunability of excitonic resonances for wavefront shaping in emerging photonic applications.