Engineering 2-photon optical data storage systems

Two-photon 3-D memories are similar to multilayer optical disk systems with the potential for simple media fabrication, many layers, parallel access for high data transfer rates, and low raw bit error rates (BER). Orthogonal intersection of the writing beams may be used, or if ultra-short (e.g. <100 femtosecond) pulses are used, a counter-propagating arrangement is feasible. While single bits may be stored and recalled, parallel access of lines or planes of data is naturally accommodated in two-photon 3-D memories, to provide increased data transfer rates. Due to diffraction of the addressing beam as it propagates across the data image, there exists a tradeoff between the volumetric density of the memory and the parallelism, or data transfer rate. We have performed a variety of 3-D memory experiments to demonstrate writing, reading, and erasure, and recently we have begun system-level characterization experiments to evaluate this technology's practical potential. The progression of this evaluation has proceeded from the demonstration of multilayer recording of "noisy" images, to the qualitative improvement of those images to the point at which more quantitative techniques are needed to measure the performance of the media, recording, and reading systems.