Sanyo Electric Co Ltd of Japan has developed a blue-violet laser diode with a pulse oscillation output power of 450mW (Fig 1). The emission wavelength is 405nm, designed to make it possible for Blu-ray Disc drives to record 4-layer discs at 12x speed. A 4-layer disc would have a storage capacity of 100 Gbytes, enough to hold about eight hours of high-definition television (HDTV) imagery. With a 12x write speed, it would be possible to dub a two-hour program in only ten minutes (Fig 2).
Blu-ray Disc drives currently use 2-layer discs at 6x speed, but increases are expected in the number of recording layers, rotation speed and other characteristics. Key causes are increased exposure to HDTV programming, and the fact that more consumer digital camcorders can also shoot digital imagery. It is likely that more users in the future will choose Blu-ray Disc to store their imagery, and that expectation is driving manufacturers to increase recording time through multi-layering, accelerate recording by boosting rotation speed and otherwise enhance products.
Sanyo Electric hopes to commercialize a 4-layer, 12x drive in two or three years, and launch volume production of the new laser at that time.
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