Abstract: An optical data storage medium includes a triple layer recording structure having an expansion layer, a retention layer and a very thin reflective layer interposed between the retention and expansion layers. The three layers are strongly bonded together so that the thermally and mechanically active expansion and retention layers can mechanically act upon each other through the intermediate reflective layer. The expansion and retention layers are dyed to selectively pass or absorb light of preselected wavelengths. The thin reflective layer is adapted to partially pass and partially reflect light of preselected wavelengths.

Abstract: An erasable optical data storage medium has an embedded servo track and a subsurface recording interface. An erasable recording structure having two dyed polymer layers is separated from the servo track by a compression layer. The servo track is formed in a hard substrate which provides mechanical support for the medium. The medium is adapted to form non-vesicular data bumps projecting into the compression layer when exposed to a write laser beam of predetermined wavelength projected through the substrate and compression layer. The embedded servo track and recording interface are sufficiently close to each to be read simultaneously in the same focal plane.