Beam coupling ratios and diffraction efficiencies of a layer-structured liquid crystal device; the effect of injection temperature and layer thickness

Abstract

Beam coupling ratios and diffraction efficiencies of a photorefractive liquid crystal cell were measured while changing the injection temperature and the layer thickness of the liquid crystal in a layer-structured fabrication. A high beam coupling ratio and first-order Raman-Nath diffraction efficiency were observed at low injection temperature and small cell gap, which showed high order parameters. However, as the cell gap was reduced, the shear stress at the interfaces between the liquid crystals and the photoconducting layers increased, so that the reorientation of the liquid crystals by an internal field could be restricted by the geometry and interrupted by a highly-induced surface energy, reducing photorefractive effects. An optimum exists in the neighborhood of 7.5 mum when LCs are injected at 25 degreesC under our experimental conditions.