Progress in second-generation holographic data storage

Holographic data storage (HDS) remains an attractive technology for big data. We report on recent results achieved with a demonstrator platform incorporating several new second-generation techniques for increasing HDS recording density and speed. This demonstrator has been designed to achieve densities that support the multi-terabyte storage capacities required for a competitive product. It leverages technology from an existing state-of-the-art pre-production prototype, while incorporating a new optical head designed to demonstrate several new technical advances. The demonstrator employs the new technique of dynamic aperture multiplexing in a monocular architecture. In a previous report, a monocular system employing angle-polytopic multiplexing achieved a recording density over 700 Gbit/in(2), exceeding that of contemporaneously shipping hard drives [1]. Dynamic aperture multiplexing represents an evolutionary improvement with the potential to increase this figure by over 200%, while still using proven angle-polytopic multiplexing in a monocular architecture. Additionally, the demonstrator is capable of two revolutionary advances in HDS technology. The first, quadrature homodyne detection, enables the use of phase shift keying (PSK) for signal encoding, which dramatically improves recording intensity homogeneity and increases SNR. The second, phase quadrature holographic multiplexing, further doubles density by recording pairs of holograms in quadrature (QPSK encoding). We report on the design and construction of the demonstrator, and on the results of current recording experiments.