Monolayer tungsten disulfide laser

When transition metal dichalcogenide (TMDC) crystals are thinned to monolayers, they undergo an indirect to direct bandgap transition, enabling rich electroluminescent and photoluminescent behaviors. Coupling and integration of TMDC monolayers with photonic crystal and distributed Bragg reflector microcavities have recently been reported with Purcell enhancement of spontaneous emission and strong light-matter interaction. However, realization of laser - a fundamental building block of optoelectronic system - remains a bottleneck, mainly due to the limited overall materials gain volume and difficulty to design efficient optical confinement structure. In fact, the quantum confinement on these layered d-electron materials leads to layer-dependent evolution of electronic structure with step like density of states for monolayers comparing to their bulk counterparts, Making TMDC monolayers a unique optical gain medium for superior lasing characteristics. Here, we report the first realization of monolayer tungsten disulfide (WS₂) laser embedded in a microdisk resonator. To reduce the 2D material lasing threshold, we utilized a whispering gallery mode resonator with a high quality factor. The Si₃N₄/WS₂/HSQ sandwich configuration provides a strong feedback and mode overlap. An excitonic laser emission has bee observed in the visible wavelength. Our work marks a major step towards monolayer-based on-chip active optoelectronics and integrated 2D photonic platforms for new optical communication and computing applications.