Diffraction Properties of Anisotropic Volume Gratings Formed in Polymer-Dispersed Liquid Crystal

The diffraction properties of highly polarized holographic polymer-dispersed liquid crystal (HPDLC) gratings fabricated by various grating formations are investigated as functions of the incidence angle of light and polarization state. Dominant anisotropic diffraction characteristics are obtained in HPDLC gratings by controlling the grating formation. Phase separation by photopolymerization to form the gratings is studied by evaluating the anisotropic diffraction and configuration of the separated phase of the gratings. The diffraction efficiency and the characteristic ratio of diffraction efficiency in polarization parallel to the grating vector to that in polarization perpendicular to the grating vector are markedly affected by liquid crystal (LC) contents. Structural analysis by optical polarization microscopy and scanning electron microscopy (SEM) is carried out to investigate the effect of the morphology of HPDLC gratings on diffraction properties. The grating morphologies are composed of fine droplets. The resultant gratings show novel diffractive performance consisting of high diffraction efficiency and polarization dependence over a wide angular range of incident light.