Polymer Dispersed Liquid Crystal Layer Research Articles

Optical diffraction gratings from polymer-dispersed liquid crystals switched by interdigitated electrodes

A spatial dependence of the refractive index perturbation induced in a 5-μm-thick polymer-dispersed liquid-crystal layer, by the use of a periodic electric field from the system of 50μm separated interdigitated electrodes, was investigated by measuring the induced in-plane birefringence of the sample. The efficiency of various diffraction orders was measured as a function of the applied voltage amplitude, and the dependence achieved for the 1st diffraction order was compared to the values calculated on the basis of the refractive index profile. The switching properties in response to the amplitude modulation of the driving voltage of various modulation depths were investigated. Our results demonstrate that a very effective phase modulation with response times considerably below 10ms can be achieved at the expense of slightly higher driving fields than needed for the bulk nematic liquid-crystal gratings.

Monte Carlo Model of Light Scattering in Polymer Dispersed Liquid Crystals: Polarization Effects and Defects

A numerical model based on the Monte Carlo protocol is developed to describe the evolution of polarized light as it propagates through a polymer dispersed liquid crystal (PDLC) layer. Incorporating the Stokes vector and the Mueller scattering matrix to represent the light polarization, the degree of polarization (DOP) was discovered to increase for decreasing droplet size, with DOP approximately 10% after four scattering events. For increasing scatterer concentration, the DOP of transmitted light decreases from perfect polarization to as much as 75% after eight interactions. Impurities and defects in the PDLC layer are simulated by assembling non-spherical droplets and are found to depolarize in the following order of efficiency: oblates > prolates > spheres.

Phase change of a plane wave propagating through polymer dispersed liquid crystal film with nanosized droplets

The coherent field propagation in a polymer dispersed liquid crystal layer is described using a method based on the Foldy-Twersky integral equation for the vector case. Expressions for a polarization-independent phase shift and the coherent transmission coefficient of such a layer containing nanodimensional nematic liquid crystal droplets are obtained. Theoretical results for the phase shift are compared to the available experimental data.

Spatial light modulators for high-brightness projection displays

We fabricated polymer-dispersed liquid-crystal light valves (PDLCLV's) consisting of a 30-microm-thick hydrogenated amorphous-silicon film and a 10-microm-thick polymer-dispersed liquid-crystal (PDLC) film composed of nematic liquid-crystal (LC) microdroplets surrounded by polymer. The device can modulate high-power reading light, because the PDLC becomes transparent or opalescent independent of the polarization state of the reading light when either sufficient or no writing light is incident on the PDLCLV. This device has a limiting resolution of 50 lp/mm (lp indicates line pairs), a reading light efficiency of 60%, a ratio of intensity of light incident on the PDLC layer to intensity of light radiated from the layer, and an extinction ratio of 130:1. The optically addressed video projection system with three PDLCLV's, LC panels of 1048 x 480 pixels as input image sources, a 1-kW Xe lamp, and a schlieren optical system projected television (TV) pictures of 600 and 450 TV lines in the horizontal and the vertical directions on a screen with a diagonal length of 100 in. The total output flux of this system was 1500 lm.

Transmittance and Spatial Optical Noise of Polymer Dispersed Liquid Crystal Layers

On the base of the optical scattering methods, the transmittance and spatial noise spectrum of polymer dispersed liquid crystal layers are etermined. We take into account optical properties of liquid crystal droplets, spatial number fluctuations of the droplets, and droplets topological ordering.