Fundamental optical properties of photonic crystal slabs in the strong coupling regime

We report on the transmission and photoluminescence (PL) properties of semiconductor-imbedded photonic crystal slabs where the photon mode is strongly mixed with the exciton mode. The samples are prepared by incorporating PbI-based inorganic-organic layered perovskites with the large oscillator strength of excitons into periodically arranged square holes on a quartz substrate. In transmission spectra, well-pronounced dips due to the excitation of quasi-guided modes are observed, when a polystyrene layer is overcoated with an appropriate thickness on the substrate. The quasi-guided and exciton modes exhibit an anticrossing with large Rabi splitting of over 100 meV, which demonstrates the formation of polaritons via the strong coupling between these two modes. In PL spectra, we found that the polariton PL is significantly enhanced where the polariton has the largest population. Thus, the optical properties of excitons can be controlled by the electromagnetic periodic boundary condition via strong coupling with a quasi-guided mode in a photonic crystal slab.