摘要：

This thesis reveals the optical properties of a one-dimensional photonic crystal with a twisted-nematic liquid crystal defect layer. The one-dimensional photonic crystal is formed from two dielectric materials with different refractive indices by means of periodically alternate evaporation deposition. As the defect layer, the alignment and orientation of the twisted-nematic liquid crystal is mediated by the alignment technique as well as an externally applied voltage. To comprehend the optical and electro-optical properties, a spectrometer is adopted in order to observe the transmittance in the visible spectrum from 400 to 800 nm.The results show that both sets of defect modes attributed to the extraordinary and ordinary components coexisting when a polarizer controlling the polarization of the incident beam is used. These two distinct sets of peaks switch between each other when the polarization angle is altered. All defect-mode peaks blueshift with increasing applied voltage. Besides, the crossed-polarizer examination reveals the polarization-selection effect and multiple interferences. Owing to the birefringent retardation and the polarization waveguiding in a mixed-mode twisted-nematic liquid crystal, a hump-like spectral undulation appears and affects the height of the defect-mode peaks. The superposition of the humps and peaks brings about the selection effect, which dramatically enhances the transmittance of the defect-mode peaks located at the middle of the humps while suppresses most peaks impartially to as low as 20% and diminishes the one sitting right in the hump valley has nearly no transmittance. The results of experiments and simulations, being in good consistence with each other, demonstrate that such a device may be used as an electrically controllable very-narrow-band monochromatic selector.

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