Optical Response of Periodically Arranged Semiconductor with Exciton Resonance

无机-有机钙钛矿半导体（C_6H_5C_2H_4NH_3）_2PbI_4（简称PEPI）即使在室温下也有很强的激子共振。用电子光刻技术将其旋涂在石英光栅上。聚苯乙烯薄膜被覆盖以保护薄膜不受潮，并支持薄膜上的波导模式。该系统可以看作是一个具有激子共振的一维光子晶体。当腔共振与激子共振相匹配时，观察到单向增强的发光。在这种情况下，与每个凹槽中的激子的耦合可以预期是同相的，这可能会产生具有超短辐射寿命的宏观相干性。通过亚皮秒泵探测量，我们发现寿命反而延长了10%。原因目前还不清楚。利用方形晶格光栅上PEPI薄膜透射光谱的角度依赖关系，确定了色散关系。我们观察到二维光子晶体具有非常慢的群速度模式。通过蒸发分子晶体三（8-羟基喹啉）铝，制备了具有不对称轮廓的光子晶体。在入射角方面确定了光谱的不对称性。我们建立了一个计算具有激子共振的光子晶体板的透射光谱和场分布的理论框架。为了使数值误差最小化，采用了散射矩阵形式。在光栅系统上测量了PEPI的亚皮秒光学响应。考虑了泵浦激光辐照下透射谱位移的下降，并分析了二次谐波产生的原因。实验证实了某些光子晶体板系统具有二阶光学非线性。

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.