A multi-layered optical disc scheme for high density storage using transparent media

A scheme for multi-layered high-density optical storage using transparent d ielectric films is presented. Information storage in the transparent storag e medium is accomplished by varying its thickness and the subsequent inform ation retrieval is achieved by performing differential interference between two probe beams that traverse two adjacent bit areas in the medium. As a d emonstration we constructed a five-layer storage sample by stacking photo-r esist coated glass substrates together and a dual probe interferometer for the readout of the stored optical bits. Apart from the successful recovery of the information from individual layers, our experiments also demonstrate d the auto-focussing capability of the scheme by monitoring the Fresnel ref lection off the dielectric interfaces within the stack. Such feature is an important pre-requisite for practical implementation of this scheme in real applications.