Textured optical storage media

A class of optical storage media is described which consists of thin films, microscopically textured by reactive ion etching. These surfaces have random arrays of decoupled columns or cones with cross-sectional dimensions less than 100 nm. This structure yields a spatially varying, graded refractive index resulting in low specular reflectance for visible wavelengths. Reflective spots ~1 μm in diameter have been produced on the surfaces by local melting with a low power laser beam. This has been demonstrated for highly stable materials such as Si and Ge with threshold energies as low as ~1 nJ. The fabrication, microstructure, writing parameters and encapsulation of the media are discussed.