December 7th, 2006
A terabyte of data on a regular DVD?
This is the promise of the 3-D Optical Data Storage system developed at the University of Central Florida (UCF). This technology allows to record and store at least 1,000 GB of data on multiple layers of a single disc. The system uses lasers to compact large amounts of information onto a DVD and the process involves shooting two different wavelengths of light onto the recording surface. By using several layers, this technique will increase the storage capacity of a standard DVD to more than a terabyte.
This technology has been developed by Kevin D. Belfield, Department Chair and Professor of Chemistry at UCF, and his colleagues in the Belfield Research Group. So how does this work?
The process involves shooting two different wavelengths of light onto the recording surface. The use of two lasers creates a very specific image that is sharper than what current techniques can render. Depending on the color (wavelength) of the light, information is written onto a disk. The information is highly compacted, so the disk isn’t much thicker. It’s like a typical DVD.
The challenge scientists faced for years was that light is also used to read the information. The light couldn’t distinguish between reading and writing, so it would destroy the recorded information. Belfield’s team developed a way to use light tuned to specific colors or wavelengths to allow information that a user wants to keep to stay intact.
Below is a picture showing how this two-photon 3D optical system reads the data. "This 3D image was reconstructed from successively two-photon fluorescence imaging (readout) of 33 XY data planes along the axial direction (1 micron distance between each image). The principle for this novel two-photon 3D optical storage device was based on a bichromophoric mixture consisting of diaryletheneand fluorene derivative, suitable for recording data in thick storage media." (Credit: Dr. Zhen-Li Huang, UCF)
This research work has been published by Advanced Materials under the title "Two-Photon 3D Optical Data Storage via Fluorescence Modulation of an Efficient Fluorene Dye by a Photochromic Diarylethene" (Volume 18, Issue 21, Pages 2910-2914, Published online on October 30, 2006). Here is a link to the abstract.
This work has also been reviewed by Rachel Pei Chin Won in Nature Photonics under the title "Two photons are better than one" (November 16, 2006). Here are more details about this "Two-Photon 3-D Optical Data Storage" system.
[The researchers] have fabricated a two-photon three-dimensional optical data system using a photochromic polymer. They show that the system is suitable for recording data in thick storage media and for providing a readout method that does not erase existing stored information — they perform 10,000 readout cycles with only a small reduction in contrast. Also, contrary to other techniques, this method allows reading and writing of data at the same wavelength, which is achieved by changing the intensity of the laser light.
Nature Photonics also describes what kind of lasers were used by Belfield and his team.
Although the authors used a relatively expensive femtosecond Ti-sapphire laser to both read and write the information, they suggest that the data could be read using cheaper nanosecond laser diodes with comparable laser intensity, making this high density data-storage system more cost effective.
But when will we able to use DVDs with a terabyte capacity? Not before several years. In fact, the researchers just received a $270,000, three-year grant from the National Science Foundation to continue its work.
In the mean time, you can still visit — virtually — Belfield's lab. In particular, you should take a look at this page about High-Density Optical Data Storage, from which the above illustration has been extracted, and a photo gallery about One vs Two-photon Excitation.
Sources: Zenaida Gonzalez Kotala, University of Central Florida, December 4, 2006; and various websites
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