Abstract: A system and method of using the same, wherein the system comprises: an optical surface having a diffractive image generating structure disposed thereon, the diffractive image generating structure itself comprising a layer of reflective material incorporating a plurality of grooved diffractive elements each having a periodic wave surface profile, the periodic wave surface profiles each having a groove alignment direction; a source of incident electromagnetic radiation arranged to illuminate the diffractive elements at an angle of incidence substantially normal to the plane of the surface of the diffractive elements; means for polarizing the radiation from the source, and means for polarizing radiation reflected from the diffractive elements; wherein the diffractive elements are configured such that, in use, polarization conversion of the incident radiation takes place, and wherein the diffractive elements are disposed in a two dimensional array of pixels to represent an image; and further wherein the means fo

Abstract: A system and method of using the same, wherein the system comprises: an optical surface having a diffractive image generating structure disposed thereon, the diffractive image generating structure itself comprising a layer of reflective material incorporating a plurality of grooved diffractive elements each having a periodic wave surface profile, the periodic wave surface profiles each having a groove alignment direction; a source of incident electromagnetic radiation arranged to illuminate the diffractive elements at an angle of incidence substantially normal to the plane of the surface of the diffractive elements; means for polarising the radiation from the source, and means for polarising radiation reflected from the diffractive elements; wherein the diffractive elements are configured such that, in use, polarisation conversion of the incident radiation takes place, and wherein the diffractive elements are disposed in a two dimensional array of pixels to represent an image; and further wherein the means fo

Abstract: A radiation absorber comprising multiple layers has a conducting base layer, and at least first and second further layers, each separated by a dielectric material, the first and second layers having patches thereon of highly conducting material, and defining resonant cavities in cooperation with the dielectric material, wherein the resonant cavities formed on adjacent layers differ in frequency. Characteristics of the patch, such as size or shape may vary on each layer to provide different resonant frequencies, and/or dielectric or magnetic properties of the dielectric material, and/or separation distance of the patches may be varied. In some embodiments, complex dielectrics may have their loss factors adapted to tune a resonant frequency, or to adapt its resonant bandwidth.

Abstract: An optical multilayer (1) comprising textured surfaces suitable for use in anti-counterfeiting and/or security applications is described.

Abstract: A radiation absorber comprising multiple layers has a conducting base layer, and at least first and second further layers, each separated by a dielectric material, the first and second layers having patches thereon of highly conducting material, and defining resonant cavities in cooperation with the dielectric material, wherein the resonant cavities formed on adjacent layers differ in frequency. Characteristics of the patch, such as size or shape may vary on each layer to provide different resonant frequencies, and/or dielectric or magnetic properties of the dielectric material, and/or separation distance of the patches may be varied. In some embodiments, complex dielectrics may have their loss factors adapted to tune a resonant frequency, or to adapt its resonant bandwidth.

Abstract: A method of optimising the sensitivity of surface plasmon ellipsometry (SPE) apparatus used to analyse a surface comprising a conducting film is disclosed. The method includes calculating a sensitivity map of plasmon ellipsometry for the film. The sensitivity map comprises data defining variations in sensitivity of the plasmon ellipsometry apparatus with angle of incidence and polarization angle of polarized light incident on the conducting film for analysis by the apparatus. The method further comprises using the sensitivity map to configure the plasmon ellipsometry apparatus with a combination of the angle of incidence and polarization angle located in a region of substantially maximum sensitivity in the sensitivity map.

Abstract: An iridescent material comprises a diffraction grating incorporating a plurality of sheets (1) of a first substantially transparent material in parallel alignment and spaced away apart by quantities of a second substantially transparent material (2), the second material having a refractive index significantly lower than the refractive index of the first material, the plates being tilted at an angle ? to an axis X and the grating having a period d(X) in the direction of axis X, the angle ? and period d being such that a second diffraction grating is provided along an axis Z, perpendicular to axis X, the second diffraction grating having a period d(Z) and consisting of ten periods or less and whereby, the diffraction conditions of the grating can be simultaneously fulfilled by electromagentic radiation of a range of wavelength thereby causing iridescence.

Abstract: A method of optimising the sensitivity of surface plasmon ellipsometry (SPE) apparatus used to analyse a surface comprising a conducting film, the method comprising calculating a sensitivity map of SPE for the film, the sensitivity map comprising data defining variations in sensitivity of said SPE apparatus with angle of incidence and polarisation angle of polarised light incident on said film for analysis by said SPE apparatus, and using said sensitivity map to configure said SPE apparatus with a combination of said angle of incidence and polarisation angle located in a region of substantially maximum sensitivity in said sensitivity map.

Abstract: An electromagnetic radiation absorber for absorbing radiation in the wavelength range ?min to ?max. The absorber has a conductor layer in contact with a dielectric layer. The conductor layer carries a plurality of apertures of sub-wavelength dimension and the thickness of the absorber is less than ?min/4n, where n is the refractive index of the dielectric. The dielectric layer may be sandwiched between two conductor layers, one of which has the structure described above. The invention is also directed to various articles comprising such an absorber.

Abstract: An iridescent material comprises a diffraction grating incorporating a plurality of sheets (1) of a first substantially transparent material in parallel alignment and spaced away apart by quantities of a second substantially transparent material (2), the second material having a refractive index significantly lower than the refractive index of the first material, the plates being tilted at an angle &thgr; to an axis X and the grating having a period d(X) in the direction of axis X, the angle &thgr; and period d being such that a second diffraction grating is provided along an axis Z, perpendicular to axis X, the second diffraction grating having a period d(Z) and consisting of ten periods or less and whereby, the diffraction conditions of the grating can be simultaneously fulfilled by electromagentic radiation of a range of wavelength thereby causing iridescence.

Abstract: A radiation emitting device includes an optical micro-cavity bounded by first and second reflective boundaries (33,39), at least one of said reflective boundaries (39) has associated therewith inhibiting means, such as an array of hillocks or dimples, to inhibit the coupling of radiation from within the micro-cavity (31) to predetermined propagation modes, such as surface plasmon polaritons, associated with at least one of the reflective boundaries.