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Description
Exciton-photon coupling in the form of self-hybridized exciton polaritons in two dimensional Ruddlesden Popper perovskite (RPP) attracts much attention because this material offers a high exciton binding energy and a large oscillator strength even at micrometer thicknesses. RPP is a naturally stacked quantum well structure where the barrier is an organic molecule with relatively low dielectric constant. The well layer is composed of metal-halide octahedra with higher dielectric constant. Therefore, both quantum and dielectric confinements contribute to the exceptionally strong excitonic features. The stack of these quantum wells can have any thickness, but the excitonic features remain intact which allows the study of Self-hybridized polaritons in the open cavity formed by the Fabry-Perot resonances interacting with excitons. This makes fabrication process simple where RPP flakes are exfoliated on top of gold or glass substrates. Here, exploiting these unique features, we have probed exciton-photon coupling in RPPs by cathodoluminescence spectroscopy. By changing the acceleration voltage of the electron beam, we have observed a change in level repulsion of polaritonic branches in momentum-resolved CL measurements. This shows that the exciton-photon coupling strength can be tailored by the energy of the electron beam. Moreover, optical measurements of photoluminescence and reflection were carried out to be compared with CL measurements in order to study the role of coherent and incoherent excitation sources. The wavelength and intensity of laser was modified, but the level repulsion in momentum-resolved photoluminescence measurement remained unchanged which demonstrates the unique role that electron beam can play to investigate exciton polaritons.