Potentiality of the Ag-In-Sb-Te phase change recording material for high density erasable optical discs

The feasibility of using Ag-In-Sb-Te phase change material for high density of directly overwritable optical discs has been studied. A linear density of 0.34 mu m/bit with a track pitch of 0.74 mu m is confirmed to be achievable with a light source wavelength of 680 nm, with an objective lens NA of 0.60 and the criteria of data-to-data jitter of less than 14% of the channel bit length. The recording characteristics are also studied using an optical system with a 635 nm red laser diode in order to investigate the attainment of a linear density of 0.267 mu m/bit which is equivalent to the DVD-ROM (read only memory) specification.