Coupling interlayer excitons to whispering gallery modes in van der Waals heterostructures

TL;DR

This paper demonstrates coupling of interlayer excitons in van der Waals heterostructures to whispering gallery modes using waveguide-coupled disk resonators, enabling efficient on-chip optoelectronic devices.

Contribution

It introduces a novel method of integrating heterobilayer excitons with whispering gallery modes in h-BN resonators for enhanced optoelectronic applications.

Findings

Successful coupling of interlayer excitons to whispering gallery modes.

High quality factors maintained despite weak oscillator strength.

Fully waveguide-coupled heterostructure devices demonstrated.

Abstract

Van der Waals heterostructures assembled from two-dimensional materials offer a promising platform to engineer structures with desired optoelectronic characteristics. Here we use waveguide-coupled disk resonators made of hexagonal boron nitride (h-BN) to demonstrate cavity-coupled emission from interlayer excitons of a heterobilayer of two monolayer transition metal dichalcogonides. We sandwich a MoSe$_{\rm 2}$ - WSe$_{\rm 2}$ heterobilayer between two slabs of h-BN and directly pattern the resulting stack into waveguide-coupled disk resonators. This enables us to position the active materials into regions of highest optical field intensity, thereby maximizing the mode overlap and the coupling strength. Since the interlayer exciton emission energy is lower than the optical band gaps of the individual monolayers and since the interlayer transition itself has a weak oscillator strength, the circulating light is only weakly reabsorbed, which results in an unaffected quality factor. Our devices are fully waveguide-coupled and represent a promising platform for on-chip van der Waals photonics.