Thermal design for reversible phase change optical storage media

An optical storage medium comprising a substrate having lands and grooves, a reversible phase change active layer approximately 1,000 Angstroms thick above said substrate, and at least one thermally conductive dielectric layer, between 1,000 and 2,000 Angstroms thick either between said substrate and said active layer or on top of said active layer, with the grooves in the substrate being of at least 5,000 Angstroms in depth to provide thermal isolation between adjacent lands and grooves.