Electronics reports Sharp has developed a blue-violet 500mW laser that could lead to triple-layer or even quad-layer Blu-ray discs. Each layer has a storage capacity of 25GB, so a quad-layer Blu-ray disc is capable of holding up to 100GB. It's unknown when this technology will hit the market.
The light is as strong as 500mW and achieves the feat by putting an aluminum oxynitride layer between the laser's crystal and the usual dielectric film meant to protect the laser, eking out more output than would normally be possible with just the dielectric element alone. It would not only allow a drive to read twice as deep as current dual-layer Blu-ray drives but would let it write at 8X speed on all four layers.