Abstract: A method of making a wide temperature-range smectic liquid crystal material comprises taking a wide temperature-range nematic mixture and doping this with a mesogenic silicon-containing material. Aspects of the invention provide wide temperature-range smectic materials and devices using the smectic materials.

Abstract: A device for controlling the polarization state of transmitted light comprises first and second cell walls enclosing a layer of a chiral liquid crystal material. The material has a uniformly orientated helical axis in the absence of an applied field, and electrodes for applying an electric field substantially normal to the helical axis. An applied electric field flexoelectrically couples to the molecules, causing distortion of the helical structure and hence changes the bulk birefringence of the cell.

Abstract: A method of making a wide temperature-range smectic liquid crystal material comprises taking a wide temperature-range nematic mixture and doping this with a mesogenic silicon-containing material. Aspects of the invention provide wide temperature-range smectic materials and devices using the smectic materials.

Abstract: A device for controlling the polarization state of transmitted light comprises first and second cell walls enclosing a layer of a chiral liquid crystal material. The material has a uniformly orientated helical axis in the absence of an applied field, and electrodes for applying an electric field substantially normal to the helical axis. An applied electric field flexoelectrically couples to the molecules, causing distortion of the helical structure and hence changes the bulk birefringence of the cell.

Abstract: A tuneable laser device comprises first and second cell walls enclosing a layer of a liquid crystal material having a helical axis substantially normal to the inner surfaces of the cell walls in the absence of an applied field. The liquid crystal contains a fluorescent, phosphorescent, luminescent or rare-earth dye. The device includes electrodes for applying a transverse electric field substantially normal to the helical axis. The invention also provides a method of electrically adjusting the peak wavelength of a photonic band edge laser comprising a chiral nematic liquid crystal material having a helical axis and a fluorescent, phosphorescent, luminescent or rare-earth dye therein and optically pumped by a suitable light source. The method comprises applying an electric field substantially perpendicular to the helical axis so as to deform the helix by means of the flexoelectric effect.

Abstract: Siloxane compounds having a smectic liquid crystal phase and the general formula ##STR1## wherein each R=alkyl, alkenyl or aryl, Q represents a monovalent group, for example alkyl, --(CH.sub.2).sub.n OM', a chiral organic group, a dye group, a non-linear optic group or the group --(CH.sub.2).sub.n L, in which L represents a siloxane group, M and M' each represent ##STR2## wherein A is carboxyl, T is CN, F or Cl and p=0 or 1, provided that when T is F or Cl x has a value of at least 2.

Abstract: A liquid crystal device wherein the liquid crystal material is a siloxane-containing compound characterised by the the general formula ##STR1## wherein R is a C.sub.1-10 alkyl or ##STR2## each R' is a C.sub.1-4 alkyl, T is ##STR3## X is an alkyl or halogen-substituted alkyl group having at least one chiral center, Y is F, m is 0, 1 or 2 and n is 10, 11 or 12. Also claimed is a device wherein the liquid crystal material is disposed between a pair of substrates.

Abstract: A liquid crystal device wherein the liquid crystal material exhibits a smectic phase and cromprises at least one siloxane compound having the general formula ##STR1## in which R=alkyl, alkenyl or aryl, Q represents a monovalent group, for example alkyl --(CH.sub.2).sub.n OM', a chiral organic group, a dye group, a non-linear optic group or the group --(CH.sub.2).sub.n L in which L represents a siloxane group, M and M' each represent ##STR2## wherein A is carboxyl, T is CN, F or Cl and p=0 or 1, provided that when T is F or Cl x has a value of at least 2.

Abstract: A liquid crystal information storage device comprising a layer of material containing a side chain polymeric liquid crystal. At least a part of the material is heated from a viscous state above its glass transition temperature, to a fluid region in which the liquid crystalline material can readily undergo field-induced alignment. The material is addressed in this fluid region so as to achieve the selective variation in texture and orientation of molecules within the material and so record information, and the material is subsequently cooled and returned to its viscous state whereupon the information is retained.