Study of size dependence of optical response due to nanoscale spatial structure of the response field

(1)我们从理论上阐明了辐射和激子在薄膜中的耦合系统的模式结构。各态的本征能量在薄区包含负移，但在某一特定厚度处跃迁到上极化激元的能量。如果在这些跃迁之前，与各个态相关的内场分量发生共振增强，则出现大的非线性响应。对于较厚的情况下，辐射衰减常数变得非常大的更高的水平，包括非偶极型激子状态。(2)通过对GaAs多层膜的时间分辨反射率测量，证实了理论预测的辐射衰减率与GaAs层数成正比。(3)我们发现纳米薄膜由于内场的纳米级空间结构而具有光学双稳性，并且由于纳米级偏振取向结构而具有新颖的光功能。

(1) We have theoretically clarified the mode structure of the coupled system of the radiation and the excitons confined in a thin film. The eigenenergies of the respective states include the negative shift at thin region, but they jump to the energies of the upper polaritons at a particular thickness for each state. If the resonant enhancement of the components of internal field associated with the respective states occurs before these jumps, the large nonlinear response appears. For the thicker case, the radiative decay constant becomes very large for the higher levels including the non-dipole type excitonic states.(2) By the time-resolved reflectance measurement of the GaAs multiple layers, we have verified that the radiative decay rate increases in proportion to the number of GaAs layers as predicted in the theory.(3) We have found the optical bistablity in nanoscale thinflim due to the nanoscale spatial structure of the internal field, and the novel photofunctions due to the nanoscale polarization orientation configurations.