Localization of Laterally Confined Modes in a 2D Semiconductor Microcavity

Abstract

Monolayer semiconductor embedded planar microcavities are becoming a promising light−matter interacting system to uncover a wealth of photonic, excitonic, and polaritonic physics at the two-dimensional (2D) limit. In these 2D semiconductor microcavities employing the longitudinal Fabry−Perot resonance, major attention has been paid to the coupling of excitons with vertically confined cavity photons; by contrast, the lateral confinement effect on exciton−photon interactions is still elusive.Here we observe the localized distribution of laterally confined modes with discrete energies in a 2D semiconductor embedded microcavity. Monolayer tungsten disulfides with equilateral triangular geometries but varied edge lengths are selected as the active media incorporated into a dielectric planar microcavity. With the shortening of the edge length, photoluminescence mappings of active regions present spatially localized emission patterns, which are attributed to the presence of in-plane triangular waveguiding resonance caused by total internal reflection at the one-dimensional closed boundary between the monolayer semiconductor and its surrounding cavity material. Unlike the conventional quantum confinement effect of native excitons appearing at the nanometer scale, the mode emission at the active-medium center exhibits apparent size-dependent features at the micrometer scale due to the optical confinement effect correlated with its photonic nature. By reducing the area of active media, single-mode dominant emission is achieved together with its nondispersive energy and improved directionality. Our work highlights the crucial role of lateral mode control in monolayer semiconductor embedded planar microcavities and encourages the investigation of the quantum billiard problem in 2D semiconductors.

Exciton–Photon Interactions in Two-Dimensional Semiconductor Microcavities

“…53 Furthermore, an electrically pumped resonant cavity light-emitting diode was fabricated, where the WSe 2 -based heterostructure was employed as the active medium and the electroluminescence magnitude was enhanced by about two orders at the resonance frequency. 70 After the introduction of the lateral confinement of the triangular active medium in a 2D semiconductor microcavity, the enhanced spontaneous emission of the center mode exhibited a clear size-dependent effect and the improved directionality, 71 indicating that the 2D semiconductor microcavity system with the lateral mode control provided an ideal platform to study the fundamental quantum billiard problems in 2D cases. Photon Lasing.…”