Holographic data storage in clear view

17 Jun 2002

Photopolymerizable glass offers a diffraction efficiency of almost 100%.

Scientists have reported the successful development of a holographic medium that is said to meet the critical requirements of commercial, high-density data storage. Pavel Cheben of Optenia in Canada and Maria Luisa Calvo of Complutense University in Madrid, Spain, describe permanent holographic storage in a photopolymerizable, organically modified silica glass in Applied Physics Letters, Vol. 78, No. 11, pp.1490-1492.

The researchers claim that their new material exhibits unprecedented sensitivity and refractive-index change on exposure to green light. They achieved this performance by dispersing a titanocene photoinitiator and a high-refractive-index acrylic monomer through a porous inorganic host (silica glass) instead of the conventional polymeric binder. This host facilitates the more efficient transport of the liquid monomer. The properties of the resulting hybrid material are such that light from the encoding laser beams causes a polymerization reaction that alters the nature of the substance wherever it passes, changing the way that successive light beams progress through that point.

The material can form high-optical-quality samples with thicknesses of several millimeters. "Our results offer a significant advance in the field of research on holographic recording materials," said the scientists. "The holograms stored in our glass are permanent and stable. We believe that the prospects are excellent for producing practical holographic-storage devices from similar organically modified sol-gel glasses."