Thermally and electrically switchable gratings based on polymer-ball-type polymer-dispersed liquid-crystal films

Abstract

We focus on the fabrication and study of controllable holographic gratings based on azo-dye-doped and undoped polymer-ball-type polymer-dispersed liquid-crystal films. Experimental results indicate that the next step of photopolymerization of the sample with the illumination of Ar+ laser beams after UV curing causes a latent density grating to be recorded. This grating is formed by a selective secondary photopolymerization. Heating and applying a voltage change the structure of the liquid crystal and induce the appearance of the latent grating. Diffraction efficiencies versus temperature, voltage, and state of polarization are studied for both dye-doped and undoped cells and are found to be quite different. This discrepancy is attributable to the reorientation effect of liquid crystals through their interaction with the photo-induced adsorption of the doped dyes on the surface of polymer balls in the dye-doped cell.

Realization of POLICRYPS Gratings: Optical and Electro-Optical Properties

“…Neglecting the weak dependence on n of the square root in the denominator, we expand sin(pn) of expression (10) up to the linear term, and get the following result:…”

“…The common goal of this kind of applications is to reach a high diffraction efficiency in gratings fabricated by simple and cheap processes. During the last decade, a lot of work has been carried out concerning the characterization of morphology and diffraction efficiency [7][8][9], as well as switching properties [10,11,5] of such devices. In order to obtain high diffraction efficiency and good optical quality gratings, it is necessary to achieve a sharp and uniform fringe morphology; many attempts have been made therefore in order to avoid those optical inhomogeneities (produced by nematic droplets) which have the same spatial scale as the wavelength of the diffracted radiation.…”

A novel light diffuser based on the combined morphology of polymer networks and polymer balls in a polymer dispersed liquid crystals film

“…[23][24][25] Polymer morphologies in the lms can be divided into polymer-network-type and polymerball-type. [26][27][28] By optimizing the light scattering performance, PDLC lms with high transmittance can be applied in solar cells, organic light emitting diodes (OLEDs) and other optical electrical devices. Yang et al have demonstrated a novel light enhancing lm based on PDLCs that can increase the light efficiency of OLEDs.…”

Mesoscale Three Dimensional Lattices Formed in Polymer Dispersed Liquid Crystals: A Diamond-Like Face Centered Cubic

“…There have been many basic studies on optical behavior [28][29][30][31], electro-optic switching [32], liquid crystal ordering [33], and polymer morphologies [34][35][36]. Within the last few years, a number of new configurations have been reported, such as those based on polymer networks [37][38][39], polarization independent switching configurations [40], smectic-A phases [41], two-photon induced polymerization renditions [42], tunable reflection modes [43], specialized holographic methods [44][45][46], diffuse reflection modes [47], azo-dye doped PDLCs [48,49], thermal switching modes [50], and total internal reflection configurations [51]. Figure 1(a) illustrates how a red, green, blue H-PDLC stack (electrically switchable color filter stack) can be used in digital imaging using a single CCD [21] and Figure 1(b) illustrates the operation of a four-channel add-drop filter for telecommunication applications [22].…”