A dual probe differential interference scheme for multi-layered high-density optical storage

Abstract

We present a new approach for multi-layered high-density optical storage using transparent dielectric films. The proposed scheme encodes the digital bits in the storage layer by varying its optical thickness and recovers the signal by performing differential interference between two probe beams that traverse two adjacent data bits. We demonstrate the feasibility of this approach by scanning two focused laser spots across the edge of an optical step and analysing the interference pattern using a matched grating filter. The system's sectioning capability which permits multi-layered data recovery has also been demonstrated by scanning a stack of two such optical steps. The use of dual probe interference offers the advantage of inherent vibration isolation as both beams pass through a common path except at the focal region where the storage medium is positioned.