Origins of spectral doublets from 2D semiconductors embedded in optical microcavities

Recent progress embedding atomically-thin materials such as monolayer transition metal dichalcogenides (TMDs) in microcavities has enabled applications such as nanolaser devices as well as novel regimes of polarization-sensitive exciton-polaritons [1]. Compared to the highly optimized III-V semiconductors typically used in microcavities, TMDs exhibit significantly more spatial inhomogeneity as well as additional tears, strains, and chemical contaminants introduced by the mechanical layer transfer process. We show how the spatial inhomogeneity of WS₂ and MoS₂ can produce spectral doublets that mimic the upper and lower polariton branches. We identify common pitfalls for misidentifying these doublets, as well as more robust measurements that can be used to distinguish the anti-crossing feature of exciton-polaritons.

[1] Chen, et al. Nature Photonics 11, 431, (2017)