Abstract

Two-dimensional (2D) materials demonstrate appealing characteristics for CW and pulsed light-emitting sources due to their strong emission and absorption properties, novel nonlinear effects, and compatibility with the silicon-on-insulator (SOI) platform [1,2]. Contemporary 2D materials have been exploited either as gain media for CW nanophotonic optical sources [1], or as ultrafast and low-power saturable absorbers enabling pulsed lasing operation [2]. In this work, we propose and numerically evaluate an integrated nanophotonic passively Q-switched lasing element in the near-infrared (NIR), which is based on a disk resonator configuration and utilizes 2D materials for providing both the gain and saturable absorption (SA) mechanisms. The MoS₂/WSe₂ transition metal dichalcogenide (TMD) hetero-bilayer is chosen as the gain medium, which is optically pumped at 740 nm (1.675 eV) and emits light at 1128 nm (1.1 eV) via an inter-layer exciton. Optical pumping is conducted by exciting a resonant cavity mode near the pump wavelength using guided light. Both the pumping and lasing processes are rigorously treated by induced electric polarization fields describing homogeneously broadened Lorentzian transitions. Overall, the TMD hetero-bilayer is a three-level gain medium described by semiclassical carrier rate equations. The Q-switched operation is achieved by additionally harnessing the ultrafast and broandband SA response of a graphene monolayer. To numerically study and design the structure, we rigorously develop a temporal coupled-mode theory framework fed by linear finite-element method simulations. Our approach enables the accurate evaluation of the lasing characteristics in a computationally efficient manner.

© 2023 IEEE