Abstract: An optical storage medium in which the effect of optical interference is utilized to provide information storage. Heating of selected portions of the optical storage medium causes a permanent change in the wavelength and intensity of the interference fringes of the optical storage medium, and those changes give rise to large changes in light reflectivity at the initial interference fringe wavelengths, and hence gives rise to an optical pattern that is readily detectable. Preferred storage medium materials include alloys of the Ge-Se-S-Te group overlaying a metallic layer.