Direct‐Bandgap Bilayer WSe₂/Microsphere Monolithic Cavity for Low‐Threshold Lasing

Abstract

Monolayer transition metal dichalcogenides (TMDs) have emerged as widely accepted 2D gain materials in the field of light sources owing to their direct bandgap and high photoluminescence quantum yield. However, the monolayer medium suffers from weak emission because only a single layer of molecules can absorb the pump energy. Moreover, the material degradation when transferring these fragile materials hinders their cooperation with the optical cavity further. In this study, for the first time, a high‐quality monolithic structure is developed by directly growing single‐domain tungsten diselenide (WSe2) bilayers on single silica microsphere (MS) cavities. Such a completely wrapped structure guides the indirect‐to‐direct bandgap transition of WSe2 bilayers, leading to a significantly improved photoluminescence intensity by about 60‐fold. Moreover, the high‐quality monolithic structure enhances the confinement factor of the cavity by more than 20‐fold. Based on the above advantages, a bilayer WSe2/MS microlaser is realized with an ultralow threshold of 0.72 W cm−2, nearly an order of magnitude lower than the existing records. The results demonstrate the possibility of using multilayer TMD materials as 2D gain media and provide insights into a new ultracompact monolithic platform of TMD material/cavity for lasing devices.

Long-range air-host plasmonic propagation with subwavelength confinement

“…As the intensity at the foot points can be even stronger, the actual F P can be even higher. Due to the strong mode confinement and Purcell effect, the nanowire dimer structure has good potential for ultracompact plasmonic active devices using atomically thick active media [27,28].…”

Van der Waals epitaxy of CsPbBr3/WSe2 heterostructure and dynamics study of exciton recombination

“…In recent years, with the advances in the growth and optical characterization of 2D materials, 2D materials are gradually showing promising applications in both photonics and optoelectronics [1][2][3][4]. Monolayer (ML) transition metal dichalcogenides (TMDCs) are typical 2D layered materials that are widely used in photodetectors [5,6], field effect transistors [7,8], and light-emitting devices [9,10] because * Author to whom any correspondence should be addressed.…”

2D Saturable Absorbers for Potential Pulse Generation in the Visible-Wavelength Band

“…Nevertheless, their limited absorption characteristics in the visiblewavelength band and low damage threshold limit their application in high-performance systems. Layered transition-metal dichalcogenides (TMDs) have also attracted extensive attention due to their layer-dependent bandgap properties and high nonlinear optical response [4,[19][20][21][22][23][24][25][26]. Compared with bulk crystals [13], the 2D materials discussed are typically layered SA samples, whose thickness-dependent carrier dynamics, high third-order nonlinear magnetization, and broadband absorption properties have shown great potential in pulsed laser systems at visible and near-infrared wavelengths, but the presence of the bandgap limits their application at long wavelengths.…”