We present a novel type of photorefractive polymer-dispersed liquid crystal (PDLC) that contains a polymer, low-molecular liquid crystals (LC's), and a photoconductive sensitizer. Photorefractivity is demonstrated by two-beam-coupling experiments with an external dc field. This material shows highly sensitive photorefractivity, and a purely refractive-index grating $\left(\mathrm{\Delta }n\ge 3.0\times {10}^{-3}\right)$ is generated by irradiation of interference light $\left(\lambda =632.8 \mathrm{nm}\right)$. The grating in the photorefractive PDLC's shows strong anisotropy, and the dynamics depends strongly on the composition. In the case of a $40:60$ weight ratio of polymer:LC's, the photorefractive PDLC's present a stable memory effect.

In this paper, we describe the principle of the three-dimensional vector holograms formed in anisotropic recording medium. The polarization states of the interference light are three-dimensionally modulated due to both the polarization interference and optical anisotropy in the recording medium. The electric field of the polarized light reorients the director and forms the three-dimensional vector hologram in anisotropic photoreactive liquid-crystal composites. The theoretical consideration reveals the formation mechanism and optical characteristics of the resultant three-dimensional vector holograms.

The polarization state of the diffraction light from the polarization holographic grating on varying the polarization conditions of the writing beams has been investigated on the basis of Jones theory. The authors found that the polarization holographic grating, which was fabricated by irradiating the two writing beams with around 0.2 of polarization ellipticity, could convert circularly polarized light into linearly polarized light, and the anisotropic phase grating under above-mentioned condition was really fabricated using the photo-cross-linkable polymer liquid crystal. This function, not observed in the conventional polarization gratings, should be widely applied as highly functionalized optical devices.

We present a simple yet efficient method to automatically fabricate the twisted nematic structure by one-step exposure on an empty glass cell coated with photocrosslinkable polymer liquid crystal (PCLC) films. The resultant photoalignment directions of two substrates can be orthogonal to each other by controlling the difference between the exposure energy for upper and lower PCLC films and the twisted nematic (TN) structure can be automatically fabricated. The vector grating liquid crystalline cell with TN structure was also fabricated by means of a developed method, and the diffraction properties were well explained by the theoretical calculation on the basis of Jones calculus.