Metal ion doped polymers as media for optical memories

Polymer materials are making an impact on optical storage technology to develop high information density and fast access type memories with a high read‐out efficiency. The principle and advantages of three‐dimensional (3‐D) data storage in the form of interference patterns (holograms) have been outlined. Three different information storage materials have been developed by doping metal ions such as Cr(VI) and Fe(III) in water‐soluble polymers, namely poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA), which need no further thermal or chemical treatment. Volume transmission holograms have been recorded in dichromated poly(vinyl alcohol) (DCPVA), ferric chloride doped poly(vinyl alcohol) (FePVA) and dichromated poly(acrylic acid) (DCPAA), with and without an electron donor (dimethyl formamide), and xanthene dyes (fluorescein, eosin Y and Rose Bengal). Different parameters influencing the holographic performance have been optimized to achieve a high real‐time diffraction efficiency (∼70%). An electron transfer process from the polymer matrix to Cr(VI)/Fe(III), leading to the photocrosslinking of the polymer in the form of an interference pattern, has been suggested as the mechanism of information storage (hologram recording) in these materials.