Observation of exciton-polariton nano-laser in encapsulated bilayer WS2

2D materials possess exceptional optical characteristics owing to their atomically thin structure. Their easy integration into nanoscale devices makes them an ideal platform for advancing nanolasers. These nanolasers operate by confining light within subwavelength cavities, leading to the formation of a new quasiparticle state called exciton-polaritons. This hybrid matter-light state facilitates laser emission. [1]Notably, 2D material-based nanolasers exhibit remarkable features, including ultra-compact design, low-threshold lasing, and the ability to tune emissions across visible and near-infrared spectra.[2] In our recent experiments, we observed compelling evidence of laser emission from an encapsulated bilayer of WS2 at cryogenic temperatures. When the sample was excited using a continuous green laser at 532 nm, a pronounced emission peak at approximately 630 nm was detected. Further measurements employing K-space lens revealed that the emission was directional and not originating from the out-of-plane direction. Notably, our power series measurements demonstrated a strong nonlinear relationship between the emission and laser power, with a potential threshold identified through logarithmic plot.

Our future research endeavors aim to measure the coherent time of this laser and how it changes below and above threshold. With the strong binding energy of excitons in 2D TMD materials, we envision the eventual realization of robust nanolasers operating at room temperature.