A reaserch Japanese group developed a new technology that promised 10x the capacity of current DVD discs (translation from Japanese text):

"...The Shizuoka university and the Toyota Research Center developed the basic technology of the large capacity optical multilayer record which can be recorded at high density of 10 times. 10 layer repeating record layer, being able to record information to depth direction is a special feature. Research is advanced as a technology ahead the optical disk technology which uses the blue laser.

The research group developed the high polymer materials, urethane, as the material which records information. On the glass baseplate the thin film of the urethane, the membrane of the transparent plastic is placed the on that. This was repeated alternately and the urethane was repeated 10 layer. Medium thickness of the whole record 20 micro at meter, is not different from the present DVD and the like. When laser light is allowed to shine, it records making use of the character of the urethane, where refractive index of light changes. When the disk of the same size as the DVD is made with the record medium which it developed, approximately 50 giga (1 giga 10 hundred million) can record the information of the byte...." NULL