Electro-optic response and switchable Bragg diffraction for liquid crystals in colloid-templated materials.

We report optical switching studies on nematic liquid crystal incorporated into structures based on self-assembled colloids. We compare the electro-optic responses of liquid crystal imbibed into colloid-templated polymers, liquid crystal imbibed in the interstitial space of colloid crystals, and conventional polymer-dispersed liquid crystals. We characterize the Bragg diffraction of our templated liquid-crystal/polymer composites as a function of electric field and measure switching times. The response of liquid crystal in connected networks differs qualitatively from that of liquid crystal in isolated cavities.

Patterned colloidal deposition controlled by electrostatic and capillary forces.

We use substrates chemically micropatterned with anionic and cationic regions to govern the deposition of charged colloidal particles. The direct observation of the colloidal assembly suggests that this process includes two steps: an initial patterned attachment of colloids to the substrate and an additional ordering of the structure upon drying. The driving forces of the process, i.e. , screened electrostatic and lateral capillary interactions, are discussed. This approach makes it possible to fabricate complex, high-resolution two-dimensional arrays of colloidal particles.

Photopolymer-filled nanoporous glass as a dimensionally stable holographic recording medium.

The holographic recording characteristics of a photopolymer-nanoporous-glass composite are reported. An M/# of 3.2 is measured in this medium by angle multiplexing of a series of plane-wave holograms. In addition, the dimensional stability of the material is demonstrated by the negligible Bragg detuning of a set of angle-multiplexed holograms recorded with varying grating tilt angles and by the relative insensitivity of the detuning to changes in temperature.