Holographic storage developments are bursting out all over it seems. Colossal Storage Corp. has revealed technology that could lead to 100TB on a $45 3.5 inch disk by 2009. It uses a technology called 3D Volume Holographic Optical Storage and programmable molecular lenses. This sounds as if it is coming from Star Trek. Before attempting to disabuse that perception let's just recap recent holographic storage announcements:-
1. Optware combines holographic storage and optical disks and implies ready manufacture of holographic disks.
2. InPhase Technologies is a company we covered here and we wrote it "is a start-up developer of holographic storage devices. (A) two-year project started in October, 2002 and includes the development and demonstration of rewritable recording materials for holographic data storage systems that offer 'ultra high storage density and data access rates'".
3.) We also mentioned Aprilis, writing that it "produces HMD and HMC holographic media. These consist of a recording medium sandwiched between two unformatted glass substrates. HMD series media comes in 120 mm disk format and in 50 x 50 mm. card format."
The Aprilis technology has a 200GB capacity. But its web site talks about 1,000GB - that's 1TB - on a CD-sized disk. Also it discusses I/O rates of 100MB/sec.
Now ColossalStorage Corp is also talking about 1TB disks.
Images not data
As this writer understands it, in all three cases the holographic storage uses the full depth of the storage medium in a 3D sense rather than just magnetised areas on its surface. It stores pages of optical information which can be reconstructed into images by the reader. Inphase says 1MB can be read and written in parallel with a single flash of light.
Company web sites talk of holographic disks replacing magnetic disks. However, a seeming characteristic of holographic storage is that the stored data is not stored in binary fashion. This implies that numeric or text information - individual bytes - cannot be written and read from a holographic disk. Holography is good for images, not for raw information.
This means that holographic storage is good for stored visual data: images; drawings; photographs; movies. It is not so good for storing bits and bytes that a computer uses to generate numbers and letters and thus data base records, word processing documents, invoices and e-mails.
We could store such data holographically but it would be akin to a micro-fiche. You could pull up and view the pages of information but not apply computer operations to them directly. A holographic page of text would need to go through a OCR-like process before you could run it through a word processor.
Unless holographic storage technology can read and write individual bits and bytes such that computer applications can work on them directly then this limitation will stay in force.
Having noted this requirement let's have a brief look at Colossal Corp's technology.
Colossal Storage's technology
It uses a very small light wavelength; 50nm ultra violet, compared to, say, the Blu-ray laser which uses a 450nm beam. Plasmon’s UDO and the Aprilis technology uses beams in the 700-500nm area. The smaller the beam spot – which is a function of its wavelength, the denser the storage.
The inventor, Michael E. Thomas, president of Colossal Storage Corporation, found that, by using an Ultra Violet Photon and an electric field it was theoretically to use the electrons (write current) to make a binary state molecule transition back and forth between the two states, forming what he terms an “Atomic Switch". It’s switched from one state to another by "Photon/Laser Induced Electric Field Poling".
Reading data is accomplished by using Ultra Violet photons of lesser quantum energy and using the resulting diffraction and interference to assess the binary state of the molecule. Apparently the molecule’s changed state and the diffracted photons enables groups of light and dark lines to be viewed as data. (It sounds like a molecular level bar code.)
The use of a 3D space for storage means billions of bits can be written and read in one operation.
Where are we?
It appears that we have three companies developing holographic storage based on optical disks which offer the potential for tens of terabytes of storage. At the least moving and still image data can be stored. If the read and write apparatus can work at the individual bit level then data could be stored, data which can be operated on by computer applications.
If the storage capacities hinted at are real then it might just be that in five years time we will be using holographic optical disks to store data rather than the magnetised hard drives we know and love today.
It is, of course, a big if. Beam me up Scotty.