Abstract: Methods of applying a pattern and security devices are disclosed. In one arrangement, a receiving member (10) having a layered structure (12) is provided. The layered structure (12) comprises a layer of phase change material (PCM, 2). The phase change material (PCM, 2)is thermally switchable between a plurality of stable states having different refractive indices relative to each other. An embossing member (5) is stamped into the receiving member (10). The embossing member (5) heats a selected portion of the layer of phase change material (PCM, 2) via contact with the receiving member (10) during the stamping. The heating thermally switches phase change material (PCM, 2) in the selected portion and thereby applies a pattern of different refractive indices to the layer of phase change material (PCM, 2).

Abstract: Provided herein is a phase change material for use in a display device. Also provided is a display device comprising a phase change material; the use of a phase change material as an optical absorber in a display device; a method of fabricating a pixel; and a method of fabricating a display device. The phase change material is as described in more detail herein.

Abstract: There is provided a chirped diffractive element (20) in the form of a grating (22) configured for supporting a plurality of guided mode resonances (54), which resonances (54) may be considered to comprise a standing wave. Chirping the grating (22) may allow guided mode resonances (54) to be distinguishable in terms of position within a section (34) the grating (22). An incident electromagnetic field may be coupled into at least one of the sections (34) when the electromagnetic field has a wavelength value within a predetermined wavelength range and a sample has a refractive index value within a predetermined index range. The incident electromagnetic field may be reflected by at least one of the sections (34) of the grating (22) exhibiting a guided mode resonance (54).

Abstract: There is provided a chirped diffractive element (20) in the form of a grating (22) configured for supporting a plurality of guided mode resonances (54), which resonances (54) may be considered to comprise a standing wave. Chirping the grating (22) may allow guided mode resonances (54) to be distinguishable in terms of position within a section (34) the grating (22). An incident electromagnetic field may be coupled into at least one of the sections (34) when the electromagnetic field has a wavelength value within a predetermined wavelength range and a sample has a refractive index value within a predetermined index range. The incident electromagnetic field may be reflected by at least one of the sections (34) of the grating (22) exhibiting a guided mode resonance (54).