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Phototriggered kinetics is investigated in the dark for holographic polymer-dispersed liquid crystal gratings. Subsequently to holographic recording, the diffraction efficiency first slightly increases, then decreases, and afterwards starts to grow again. The remarkable growth continues for several days until the diffraction efficiency stabilizes at values several times larger than the initial ones. The initial increase is attributed to a dark polymerization reaction as confirmed by electron paramagnetic resonance spectroscopy. The slow process is associated with the kinetics of a phase-separation mechanism. The non-monotonic behaviour of the diffraction efficiency is explained by superposition of refractive-index and extinction modulations. [ABSTRACT FROM AUTHOR]

Strong polarization-conserving holographic scattering was observed in a photopolymer-dispersed liquid crystal film fabricated from the UV curable mixture of commercially available constituents. During the photopolymerization process a bright corona of diffracted light evolves around the pump beam. The intensity of the rotationally symmetric light distribution increases upon exposure. By rotating the sample, two characteristic diffraction rings appear which can be explained by the Ewald sphere construction. Our results demonstrate that the associated parasitic holograms are very pronounced. Hence, their presence must be accounted for whenever preparing and utilizing holographic polymer-dispersed liquid crystals in any application. [ABSTRACT FROM AUTHOR]