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Abstract

An optical data storage medium is disclosed for use in an optical read/write system using an optical read wavelength of W, the medium including a textured region having raised areas and depressed areas disposed in a regular array with a period (pitch) not greater than W and a depth (peak-to-trough) in the range 10 to 1,000 nanometers. The medium comprises a substrate and a regular array of zones of magneto-optic material disposed at least over the peaks and troughs of the surface texture and conforming to the surface texture. In many embodiments, there is also a layer or a regular array of zones of an optically reflective material. In one embodiment, the texture is shallow, being generally in the range 10 to 120 nanometers. In a second embodiment, the depth of the texture is at least one tenth of the value of W. In any of the embodiments, there may be a dielectric layer over the top of the structure. The texture can take the form of a grating, or of crossed gratings, or be defined between an array of protuberances; structures with sinusoidal, square-wave (top-hat) or saw-tooth profile are advantageous.

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