A computer disc about the size of a DVD that can hold 60 times more data is set to go on sale in 2006. The disc stores information through the interference of light – a technique known as holographic memory.
The discs, developed by InPhase Technologies, based in Colorado, US, hold 300 gigabytes of data and can be used to read and write data 10 times faster than a normal DVD. The company, along with Japanese partner Hitachi Maxell announced earlier in November that they would start selling the discs and compatible drives from the end of 2006.
“Unlike other technologies, that record one data bit at a time, holography allows a million bits of data to be written and read in parallel with a single flash of light,” says Liz Murphy, of InPhase Technologies. “This enables transfer rates significantly higher than current optical storage devices.”
The discs, at 13 centimetres across, are a little wider than conventional DVDs, and slightly thicker. Normal DVDs record data by measuring microscopic ridges on the surface of a spinning disc. Two competing successors to the DVD format – Blu-ray and HD-DVD – use the same technique but exploit shorter wavelengths of light to cram more information onto a surface.
Holographic memory, by contrast, stores information in a light-sensitive crystal material using the interference of laser light. The process involves splitting a single light beam into two and then passing one through a semi-transparent material. This is a grid that acts like a filter, changing different parts of the beam to encode bits of information.
The altered beam and the reference beam are then recombined in the light-sensitive material and their pattern of interference provides a record of the encoded information. Information can be recorded and retrieved so rapidly because many bits of data can be recorded and read in parallel.
InPhase says the technique could theoretically be used to store up to 1.6 terabytes of data on the same size of disc and to read data at 120 megabits per second. This is 340 times the capacity of an ordinary DVD and 20 times the data rate.