We report on the formation of switchable holographic transmission gratings in polymer-dispersed liquid-crystal cells by use of the 633-nm wavelength of a He-Ne laser. We present results for the structure, diffraction efficiency, and switching characteristics of the gratings.

We present results for the effects of a crosslinking agent, cure temperature, and UV flux on the electro-optical properties of polymer-dispersed liquid crystal (PDLC) cells. These cells were fabricated using a mixture of a liquid crystal (E8) and an acrylic monomer (CN135). The maximum in the first derivative of the transmission vs. applied, sinusoidal voltage (inflection voltage, V inf ), varies systematically with PDLC formulation and cure-process conditions. For PDLC cells fabricated with a crosslinking agent (SR295), V inf increases with increasing the concentration of SR295. However, for cells fabricated without the use of a crosslinking agent, V inf decreases with increasing the UV flux and decreasing temperature.

We describe the production of a high speed, and high stroke, phase modulator using a polymer network liquid crystal device. We present data showing fast response times (sub millisecond) in a device which can operate at visible wavelengths with a simple electrical addressing scheme.

Bragg reflection gratings are holographically recorded in polymer-dispersed liquid crystal materials by using the 632.8-nm wavelength of the He-Ne laser. Mixtures of the commercially available E8 nematic liquid crystal, pentafunctional monomers, and photooxidant dye methylene blue are employed. We demonstrate that Bragg reflection gratings can be formed in this acrylate photopolymer system with reflection efficiencies of 52% with a peak notch at 1165 nm. We also present results for the switching characteristics of these gratings with switching fields on the order of 6MV∕m and rise times of 62μs.

We investigate the effects of monomer functionality on the formation and switching characteristics of holographic transmission gratings in polymer-dispersed liquid-crystal cells fabricated by using the 633 nm wavelength of an He-Ne laser. We present results for the microstructure, diffraction efficiency eta, and switching characteristics of gratings formed with acrylate monomers of functionalities ranging from 2 to 4. The microstructure and diffraction efficiency are sensitive to functionality; both improve with increasing functionality. For functionalities of 2.5 or more, eta approaches 34% and can be switched off with electric fields of about 20 MV m(-1).