Multilayer thin-film holographic storage-a new approach

Optilink has developed and presented a polarization holographic reading writing system using 1-2 /spl mu/m thick storage layer on a card form media. A storage density of 1.3 bit//spl mu/m/sup 2/ has been achieved without multiplexing with sparse code modulation and Fourier-filtering. Because of the use of a thin storage layer, the volume data density is extremely high in the system. Further enhancement of the areal density up to /spl sim/100 bit//spl mu/m/sup 2/ can be achieved in an improved new polarization holographic system using a multilayer media instead of the thin film. A 6f system for reading with a suitable second spatial filter allows separation of the signal from different layers. This technique combines the advantage of the thin film holography with the idea of the confocal filtering.