Abstract: A light-emitting device includes a substrate, a light-emissive layer disposed over the substrate, and a grating for aligning the light-emissive layer. The grating aligns molecules of the emissive layer, so that the device emits polarised. The grating also reduces wave guiding effects in the device, so increasing the useful light output of the device. The light-emitting device may be an organic light-emitting device (OLED). The grating may align substantially the entire area of the light-emissive layer in a first direction. In this case, substantially the entire emissive area of the device will emit layer of a single polarisation. Alternatively, the grating may align a first region of the light-emissive layer in a first direction and may align a second region of the light-emissive layer in a second direction different from the first direction.

Abstract: A light-emitting device comprises a substrate (13), a light-emissive layer (15) disposed over the substrate, and a grating (17) for aligning the light-emissive layer (15). The grating (17) aligns molecules of the emissive layer (15), so that the device emits polarised. The grating also reduces wave guiding effects in the device, so increasing the useful light output of the device.

Abstract: A reflective liquid crystal device comprises a polarizer and a mirror between which are disposed several retarder. At least one of the retarders is a variable liquid crystal element whose optic axis is switchable so as to switch the device between a reflective state and a non-reflective state. In the non-reflective state, the total retardance of the retarders between the polariser and the mirror is equal to an odd number of quarter wavelengths for a wavelength at or adjacent the middle of the visible spectrum.

Abstract: A reflective liquid crystal device comprises a polariser and a mirror between which are disposed several retarder. At least one of the retarders is a variable liquid crystal element whose optic axis is switchable so as to switch the device between a reflective sate and a non-reflective state. In the non-reflective state, the total retardance of the retarders between the polariser and the mirror is equal to an odd number of quarter wavelengths for a wavelength at or adjacent the middle of the visible spectrum.

Abstract: A reflective liquid crystal device includes a polarising beam splitter, a polarisation preserving reflector and a retarder arrangement including at least two retarders. A first of the retarders is disposed between the beam splitter and the reflector, and a second of the retarders is disposed between the first retarder and the reflector, and at least one of the first and second retarder including a liquid crystal layer which is switchable between a dark device state and a bright device state. In the dark state, the retarder arrangement rotates the plane of polarisation of plane-polarised light directed by the beam splitter towards the reflector by substantially n.times.180.degree., where n is an integer, and in a bright device state the first retarder has a retardation of substantially .lambda./2 and the second retarder has a retardation of substantially .lambda./4.

Abstract: A wavelength-selective arrangement interacts with optical radiation propagating in a transmission medium. The arrangement includes a selector member made of a polar organic material which exhibits piezoelectric properties, the selector member having an interaction surface for interacting with the radiation. The selector member is provided with structure for propagating surface acoustic waves along the interaction surface so as to create a grating and thereby determine its interacting properties in relation to the wavelength of the radiation, in a selectively variable manner.