While it may not be used for the PlayStation 4 which may utilize optical storage discs, Sony is currently developing new laser technology that is reportedly far superior to conventional Blu-ray discs.
According to Examiner.com (linked above), the new Sony laser tech is said to offer roughly 20 times the capacity of current Blu-Ray discs.
To quote: "The development team of Tohoku University and Sony has completed work on a new laser technology offering 20 times the capacity of current Blu-Ray discs.
The most difficult aspect, if I can make sense of the Google translation as well as I think I can, was reducing the size of the equipment needed to produce such a strong beam of light down to the size of commercial products.
Currently the technology can only be used in experimental prototypes costing over $100,000 to produce. Sony plans to have the laser available to consumers within a few years."
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