FORGET Blu-ray. Discs which can store 20 times as much data in 3D holograms just moved a step closer, thanks to better materials.
To write the data, two laser beams are aimed at a disc of light-sensitive polymer. One beam has been encoded with patches representing 0s and 1s by shining it through a digital 鈥渕ask鈥�. At the point in the disc where the beams intersect, they interfere with each other to create islands of bright light and regions of darkness. Where the lasers鈥� interference pattern creates bright areas on the disc, small monomer molecules link up to form chains with a different refractive index. The data is stored in this pattern, which like a hologram can be read back with another laser.
One initial problem was that the polymers from which the discs are made tend to shrink during this process, creating distortions that make it difficult to read the data back. So Craig Hawker鈥檚 team at the University of California, Santa Barbara, have replaced the small monomers with larger ones. Because these take up more space, fewer bonds form between them, reducing this shrinkage and eliminating distortions, Hawker says (Chemical Communications, ).
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