Abstract: The invention provides a mould (80) comprising first (82), second (84) and third (86) cuboid moulds elements, each having a pair of adjacent rectangular faces which are planar and polished flat and which intersect at 270° to a high tolerance. Each mould element has a length dimension substantially twice its width dimension so that the mould elements may be arranged to form two accurate internal corner-cubes having flat, planar surfaces suitable for moulding. The apexes of the two internal corner-cubes are co-located. Pairs of adjacent mould elements are clamped in contact with each other by means of bolts (88) and washers (89). The mould may be used to produce a component having a very accurate solid corner-cube, whilst the mould elements themselves are relatively simple to fabricate because each is required to have only a pair of adjacent rectangular surfaces which are flat and planar and which intersect at 270° to a high tolerance.

Abstract: An optical tag (200) comprises a chalcogenide glass corner-cube reflector (202) bonded to a silicon MEMS modulator (206) by means of a glass material (214) having a lower softening temperature than that of the reflector. The tag is provided with AR coatings (210, 212). The invention provides a robust, integrated and compact optical tag having a wide field of view and low manufacturing costs.

Abstract: An optical substrate is provided with a surface of a desired shape by coating the surface with a thin layer of an optical glass and subsequently modifying the shape of the external surface of the layer. In preferred embodiments, the temperature of the substrate is maintained at substantially less than 400° C., the substrate is an optical component other than a simple window, and the refractive index o the optical glass is within 20% of the refractive index of the material providing the surface to be coated. One particular use is when both the substrate (e.g. a non-linear optical layer) and the optical glass are optically transmissive in the near infra-red and/or mid infra-red ranges. The glass layer can compensate for physical imperfections in the surface. It can be polished to optical quality, or provide with detail across the coated surface, e.g. as a “moth-eye” anti-reflection layer, or a diffractive or interference structure.