An optical data storage system is contemplated, one employing a data-modulated writing laser beam and a non-erasing reading laser beam of predetermined wavelength. Improved optical media (10) for such systems are described, these characterized by multiple layers (12, 13, 14, 15) whose optical characteristics and thickness are chosen to accomodate a prescribed writing and reading energy and wavelength and so provide an anti-reflection condition for unrecorded portions of the medium and a relatively higher reflectivity for recorded portions. A preferred optical medium (10) includes a highly reflective aluminum layer (13), a relatively transparent polymer spacer layer (14) overlying the reflective layer (13), and an absorber layer (15) overlying the nucleation layer, the absorber layer (15) being rendered in an island configuration, adapted to be so affected by the contemplated write beams as to "agglomerate" and better transmit the read beam.