Theory of Nonlinear Excitonic Response of Hybrid Organic Perovskites in the Regime of Strong Light-Matter Coupling

We present a quantitative study of the nonlinear optical response of layered perovskites placed inside planar photonic microcavities in the regime of strong light-matter coupling, when excitonic and photonic modes hybridize and give rise to cavity polaritons. Two sources of nonlinearity are specified, the saturation of the excitonic transition with increase of the optical pump and Coulomb interaction between the excitons. It is demonstrated that a peculiar form of the interaction potential, specific to the multilayer structure of organic perovskites, is responsible for the substantial increase of the exciton binding energy and Rabi splitting with respect to conventional semiconductor systems. This results in a dominant contribution of the Rabi splitting quench effect in the nonlinear optical response. Moreover, due to the tightly bound character of excitons, the density of Mott transition is essentially higher, allowing extremely large polariton blueshifts of about 20 meV to be reached, which is an order of magnitude higher than in conventional semiconductors.