Nonlinear interactions between excitons strongly coupled to light are key for accessing quantum many-body phenomena in polariton systems. Atomically-thin two-dimensional semiconductors provide an attractive platform for strong light-matter coupling owing to many controllable excitonic degrees of freedom. Among these, the recently emerged exciton hybridization opens access to unexplored excitonic species, with a promise of enhanced interactions. Here, we employ hybridized interlayer excitons (hIX) in bilayer MoS2 to achieve highly nonlinear excitonic and polaritonic effects. Such interlayer excitons possess an out-of-plane electric dipole as well as an unusually large oscillator strength allowing observation of dipolar polaritons (dipolaritons) in bilayers in optical microcavities. Compared to excitons and polaritons in MoS2 monolayers, both hIX and dipolaritons exhibit ≈ 8 times higher nonlinearity, which is further strongly enhanced when hIX and intralayer excitons, sharing the same valence band, are excited simultaneously. This provides access to an unusual nonlinear regime which we describe theoretically as a mixed effect of Pauli exclusion and exciton-exciton interactions enabled through charge tunnelling. The presented insight into many-body interactions provides new tools for accessing few-polariton quantum correlations.

Nonlinear interactions between excitons strongly coupled to light are key for accessing quantum many-body phenomena in polariton systems [1][2][3][4][5]. Atomically-thin two-dimensional semiconductors provide an attractive platform for strong light-matter coupling owing to many controllable excitonic degrees of freedom [6][7][8][9][10]. Among these, the recently emerged exciton hybridization opens access to unexplored excitonic species [11][12][13][14][15], with a promise of enhanced interactions [16]. Here, we employ hybridized interlayer excitons (hIX) in bilayer MoS 2 [11-14] to achieve highly nonlinear excitonic and polaritonic effects. Such interlayer excitons possess an out-of-plane electric dipole [12] as well as an unusually large oscillator strength [11] allowing observation of dipolar polaritons (dipolaritons [17-19]) in bilayers in optical microcavities. Compared to excitons and polaritons in MoS 2 monolayers, both hIX and dipolaritons exhibit ≈ 8 times higher nonlinearity, which is further strongly enhanced

This study uses a laser patterning setup to write defect structures into a conjugated polymer microcavity. We show that the defect enhances optical confinement and reduces the lasing threshold.