Advanced materials for high-density optical storage

Abstract

High storage density optical disk is expected as the key device for storage at the dawn of the full-scale multimedia age. It meets the requirement of a large storing capacity to record and retrieve great amounts of data including motion pictures, audio information and data for computer processing. The advanced storage media are the most important means for high density optical disk storage. According to optical diffraction limitation the diameter of the focused spot is proportional to (lambda) /NA, where (lambda) is writing and reading laser wavelength and NA is optical numerical aperture of focusing lens. Therefore, the practical approach for minimizing the mark length is to decrease (lambda) and to increase NA. There are three steps for decreasing laser wavelength from 780 - 800 nm used now to 630 - 650 nm (red diode lasers) and then to 400 - 500 nm (blue-green lasers). The advanced storage materials should be sensitive, stable and with recording performances at 630 - 650 nm and 400 - 500 nm laser wavelength regions. This paper reports our progress of three kinds of advanced storage materials for high density optical disks, there are: magneto-optical, phase change and organic storage materials. The main attention is put on rewritable (erasable) optical storage.