Capacity of a 3-D multi-layer optical data storage system

A high capacity 3D multi-layer optical data storage system is being developed at Call/Recall, Inc. A single beam two-photon recording technique is used to record data tracks and layers within a monolithic thick plastic disk (D.A. Parthenopoulos and P.M. Rentzepis, Science vol. 245, pp. 843-845, 1989; H. Zhang et al., Proc. SPIE vol. 4090, pp. 174-178, 2000). The recorded bits emit broadband fluorescence when excited by a laser beam within the absorption band of the written molecule. The recorded volume has no noticeable index change in the visible spectrum. The recorded bits are non-reflective for the readout beam and recording beam. These properties allow the recording and readout beams to access multiple layers in parallel (H. Zhang, 18th IEEE Symp. Mass Storage Systems, pp. 225-236, 2000; E.P. Walker et al., ODS 2002; E.P. Walker et al., ODS 2001, Proc. SPIE, 2001). The capacity of the two-photon 3D multi-layer optical data storage system is influenced by the recorded bit volume, track pitch and layer separation.