Giant Out-of-Plane Exciton Emission Enhancement in Two-Dimensional Indium Selenide via a Plasmonic Nanocavity

Out-of-plane (OP) exciton-based emitters in twodimensional semiconductor materials are attractive candidates for novel photonic applications, such as radially polarized sources, integrated photonic chips, and quantum communications. However, their low quantum efficiency resulting from forbidden transitions limits their practicality. In this work, we achieve a giant enhancement of up to 34000 for OP exciton emission in indium selenide (InSe) via a designed Ag nanocube-over-Au film plasmonic nanocavity. The large photoluminescence enhancement factor (PLEF) is attributed to the induced OP local electric field (Ez) within the nanocavity, which facilitates effective OP exciton- plasmon interaction and subsequent tremendous enhancement. Moreover, the nanoantenna effect resulting from the effective interaction improves the directivity of spontaneous radiation. Our results not only reveal an effective photoluminescence enhancement approach for OP excitons but also present an avenue for designing on-chip photonic devices with an OP dipole orientation.

Automated summary

A giant enhancement of up to 34000 for out-of-plane (OP) exciton emission in indium selenide (InSe) is achieved via a designed plasmonic nanocavity consisting of a silver nanocube over a gold film. The large enhancement is attributed to the induced OP local electric field (Ez) within the nanocavity, which facilitates effective OP exciton-plasmon interaction. The nanoantenna effect resulting from the interaction also improves the directivity of spontaneous radiation, providing a potential avenue for designing on-chip photonic devices with an OP dipole orientation.