Abstract
Recently, cholesteric liquid-crystalline (CLC)-semiconductors have been studied for the purpose of realizing circularly polarized light (CPL) emission by electrical pumping. In this study, we investigated the one- and two-photon excited CPL emission properties of glassy CLC film of oligo (p-phenylenevinylene) derivatives. In the case of one-photon excitation, the CPL emission spectra were significantly different between the forward and backward configurations of the detector to the excitation light. This is because spontaneous emission occurred near the sample surface due to the large absorption coefficient for the excitation light. In contrast, in the case of two-photon excitation, the CPL emission spectra in the forward and backward configurations were almost identical. This is because the absorption coefficient for two-photon excitation was smaller than that for one-photon excitation, and spontaneous emission occurred over the entire sample. This result indicates that two-photon excitation is a useful optical pumping method for spectral analysis in CLC-semiconductors.
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