Out-of-plane emission of trions in monolayer WSe2 revealed by whispering gallery modes of dielectric microresonators

TL;DR

This paper introduces a spectroscopic technique using whispering gallery modes to identify out-of-plane dipole emissions in monolayer WSe2, revealing trions as the source, which advances on-chip photonic applications.

Contribution

It presents a novel method to detect out-of-plane dipoles in 2D materials and demonstrates trions as the emission source in monolayer WSe2 at room temperature.

Findings

Out-of-plane dipoles in monolayer WSe2 identified

Trions are responsible for out-of-plane emission

Method enables better integration of 2D materials in photonics

Abstract

The manipulation of light emitted by two-dimensional semiconductors grounds forthcoming technologies in the field of on-chip communications. However, these technologies require from the so elusive out-of-plane photon sources to achieve an efficient coupling of radiated light into planar devices. Here we propose a versatile spectroscopic method that enables the identification of the out-of-plane component of dipoles. The method is based on the selective coupling of light emitted by in-plane and out-of-plane dipoles to the whispering gallery modes of spherical dielectric microresonators, in close contact to them. We have applied this method to demonstrate the existence of dipoles with an out-of-plane orientation in monolayer WSe2 at room temperature. Micro-photoluminescent measurements, numerical simulations based on finite element methods, and ab-initio calculations have identified trions as the source responsible for this out-of-plane emission, opening new routes for realizing on-chip integrated systems with applications in information processing and quantum communications.