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We present the results of an extended investigation performed on holographic reflection gratings recorded in blue sensitive polymer dispersed liquid crystals in view of a possible application in optical data-storage. The analysis has been performed by means of real-time spectroscopy during the polymerization process. The analysis of transmission spectra during the recording process showed a fast photopolymerization, resulting in the rapid formation of a reflection peak. Gratings characterized by high spatial frequency (> 7000 lines/mm), high diffraction efficiency (up to 50%) and large refractive index modulation (Δn ∼ 0.008) have been obtained. Unfortunately, the monomer conversion into a polymer network is generally characterized by a strong packing, with a consequent reduction in volume (polymerization shrinkage). This phenomenon induces a significant blue-shift of the reflected wavelength. With the aim of better understanding and possibly reducing the shrinkage, a new high-sensitive experimental technique has been developed to measure shrinkage effects in multi-component polymeric mixtures. [ABSTRACT FROM AUTHOR]

We report optical characterization of holographic reflection grating recorded in Nano-PDLC in view of their application as basic materials for a new generation of optical disk. The evaluation of the critical parameters of the holographic materials has been achieved by analyzing the experimental data through the existing theories. The procedure allows to evaluate: diffraction efficiency, sensitivity, index modulation, optical shrinkage, absorption. The recorded gratings fulfill most of the requirements for this application. [ABSTRACT FROM AUTHOR]

We report the fabrication technique and the main emission properties of two novel all-organic laser devices based on high-resolution reflection gratings written on holographic polymer-dispersed liquid crystal materials by means of conventional holographic techniques. The first type of laser is based upon a distributed Bragg-reflector configuration whereas the second one makes use of a distributed-feedback configuration. Different monomer/liquid-crystal/photoinitiator mixtures are analysed and the main parameters affecting the grating reflectivity and the overall performances of these plastic mirrorless laser device are discussed. [ABSTRACT FROM AUTHOR]

A detailed study of the light-induced gratings in Methyl-Red-doped 4-n-pentyl-4'cyanobiphenyl (5CB) homeotropically aligned is reported. In particular, the dependence of diffraction efficiency upon the pump and probe polarizations has been investigated both for transient and permanent gratings. Our results confirm the earlier observations on the role of light-induced adsorption of MR molecules on the cell boundaries and demonstrate the common origin of the supranonlinear response and the permanent recording effect. [ABSTRACT FROM AUTHOR]

We report the realization and the characterization of an all-optical switching device based on a transmission grating recorded in a polymeric substrate infiltrated with a methyl red-doped liquid crystal. The properties of this highly nonlinear mixture are exploited to modulate the diffraction of the grating by a pump beam when a static electric field is applied. The behavior of the device is in agreement with the existing model for methyl red-doped liquid crystals. [ABSTRACT FROM AUTHOR]

Abstract: We report diffraction gratings recording in polymer dispersed liquid crystals (PDLC) material with a beam suffering total internal reflection from the sample air surface. The real time diffraction efficiency kinetics as well as the polarization, voltage behavior and angular selectivity of the gratings are studied at different reconstruction geometries. An increase of three times of the diffraction efficiency in case of applied voltage is observed for one of these geometries in opposite to typical PDLC switchable gratings. Such dependence appears in most of the geometries and is connected to the specific formation of two gratings by the Stetson scheme. [Copyright &y& Elsevier]