Temperature-dependent excitonic light manipulation with atomically-thin optical elements

TL;DR

This study explores how excitonic decay rates and temperature influence the focusing efficiency of atomically-thin lenses made from monolayer WS2, revealing temperature-dependent excitonic effects on nanophotonic device performance.

Contribution

It demonstrates the impact of exciton decay dynamics and temperature on the optical efficiency of 2D excitonic metasurfaces, providing new insights into excitonic light scattering mechanisms.

Findings

Focusing efficiency depends on excitonic decay rates.

Cryogenic temperatures enhance optical efficiency.

Exciton-phonon scattering influences wavefront shaping.

Abstract

Monolayer 2D semiconductors, such as WS2, exhibit uniquely strong light-matter interactions due to exciton resonances that enable atomically-thin optical elements. Similar to geometry-dependent plasmon and Mie resonances, these intrinsic material resonances offer coherent and tunable light scattering. Thus far, the impact of the excitons temporal dynamics on the performance of such excitonic metasurfaces remains unexplored. Here, we show how the excitonic decay rates dictate the focusing efficiency of an atomically-thin lens carved directly out of exfoliated monolayer WS2. By isolating the coherent exciton radiation from the incoherent background in the focus of the lens, we obtain a direct measure of the role of exciton radiation in wavefront shaping. Furthermore, we investigate the influence of exciton-phonon scattering by characterizing the focusing efficiency as a function of temperature, demonstrating an increased optical efficiency at cryogenic temperatures. Our results provide valuable insights in the role of excitonic light scattering in 2D nanophotonic devices.