Strong photoluminescence enhancement in indirect bandgap MoSe$_2$ nanophotonic resonator

TL;DR

This paper demonstrates the fabrication of nanophotonic resonators from bulk MoSe$_2$, an indirect bandgap material, achieving significant photoluminescence enhancement and revealing potential for advanced nanophotonics applications.

Contribution

It introduces a novel resistless lithography method to create WGM resonators from bulk MoSe$_2$, enabling PL enhancement from indirect bandgap TMDs.

Findings

Photoluminescence enhancement factor of 100 in resonators

Confirmation of WGM spectra through experiments and modeling

Resonators amplify both direct and indirect PL components

Abstract

Transition metal dichalcogenides (TMDs) is a promising platform for new generation optoelectronics and nanophotonics due to their unique optical properties. However, in contrast to direct bandgap TMDs monolayers, bulk samples have an indirect bandgap that restricts their application as light emitters. On the other hand, the high refractive index of these materials seems ideal for creating high-quality nanophotonic resonators with a strong Purcell effect. In this work, we fabricate Whispering-gallery mode (WGM) resonators from bulk (i.e., indirect bandgap) MoSe$_2$ using resistless scanning probe lithography and study their optical properties. Micro-photoluminescence($\mu$-PL) investigation revealed WGM spectra of resonators with an enhancement factor of 100 compared to pristine flake. Scattering experiments and modeling also confirm the WGM nature of spectra observed. Temperature dependence of PL revealed two components of photoluminescence. The first one quenches with decreasing temperature, the second one does not and becomes dominant. Therefore, this suggests that resonators amplify both direct and temperature-activated indirect PL. Thus, here we demonstrated the novel approach to fabricating nanophotonic resonators from bulk TMDs and obtaining PL from indirect bandgap materials. We believe that the suggested approach and structures have great prospects in nanophotonics.