Optical Response of Periodically Arranged Semiconductor with Exciton Resonance

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Inorganic-organic perovskite semiconductor (C_6H_5C_2H_4NH_3)_2PbI_4 (abbreviated as PEPI) has strong exciton resonance even at room temperature. It was spincoated on a quartz grating fabricated by electron lithography technique. Polystyrene film was overcoated to protect film from moisture and to support a waveguide mode on the film. This system can be regarded as an one-dimensional photonic crystal stab with exciton resonance.When a cavity resonance matches to the exciton resonance, a unidirectional enhanced luminescence was observed. In this condition coupling with excitons in each grooves can be expected to be in phase which may give rise to macroscopic coherence with ultrashort radiative lifetime. By means of subpicosecond pump-probe measurement, we found out that the lifetime was on the contrary 10% longer. The reason is not clear at this stage.A dispersion relation was determined from angle dependence of the transmission spectra on PEPI film on square lattice gratings. We observed a mode with very slow group velocity, which is characteristic to two-dimensional photonic crystal.By evaporating molecular crystal tris (8-hydroxyquinoline) alminum, we have fabricated photonic crystal with asymmetric profile. Optical spectra were confirmed to be asymmetric in terms of incident angle.We have established a theoretical framework to calculate transmission spectra and field distribution of photonic crystal slab with an exciton resonance. The scattering matrix formalism was employed to minimize the numerical error.Subpicosecond optical response was measured for PEPI on grating system. A dip in transmission spectrum shifts under pump laser irradiationThe origin of second harmonic generation was considered. It was experimentally confirmed that some photonic crystal slab systems can have second order optical nonlinearity.