TEXTURED SURFACES: OPTICAL STORAGE AND OTHER APPLICATIONS.

Textured surfaces consisting of submicron columns or cones have been formed in a variety of surfaces using reactive ion etching. On metals, insulators, and semiconductors this texturing forms a graded index matching layer which reduces reflection of visible light to as low as 0. 1%. The optical properties can be permanently altered on an approximately 1 mu m size scale by irradiation with a low power laser beam and this has been explored as a new optical storage medium. The light energy transforms the optically absorbing textured surface to a nonabsorbing smooth one by melting. Reflectance changes of greater than a factor of 100 have been demonstrated at approximately 10 mw light power. The textured surfaces have also been used with dielectric materials to create high transparency optical elements. Highly absorbing films of Ge and Si have been studied as optical storage media.