Holographic storage

Mmm... Holographic storage. Not only is it actually cool, but it sounds cool too.

And while the word 'holographic' possibly conjures up memories of multi-hued holograms stuck to cards and cereal boxes in the 80s, the truth is those marvellous tilt-able images belie the science that founded them, the type of science that can make sci-fi concepts like Babylon 5's data crystals a sci-reality (yes, I really do take every opportunity to pimp Babylon 5. Have you watched it yet? Go, go now!)

And, kinda like data crystals, holographic storage is pushing boundaries in the realm of removable, portable, media. There are good bets it'll be the next Blu-ray, and it certainly puts it to shame in terms of specs.

But first a little history.

Pure light
Like many fantabulous technologies covered here in X-Ray, holographic storage isn't as new as it sounds. Indeed, the first holograms that recorded a 3D image were made in 1962 by scientists in both Russia and the USA after advances in laser technology, and the pure intense light they produced, which made it easier to create and view them.

Prior to this, it wasn't possible to easily generate the monochromatic light used to create them and the only holograms before the revolution of the laser were made by the man who discovered them - a Hungarian born British scientist by the name of Denis Gabor in 1947. Gabor had first theorised about holograms while trying to increase the resolution of some of the first electron microscopes. He later created holograms on film transparencies using a mercury arc lamp, the brightest and most coherent light source he could find at the time. It was Gabor who coined the term 'hologram' based on the Greek works 'holos' meaning 'whole' and 'gramma' meaning 'message'.

The mercury arc lamp wasn't coherent enough to make holograms of any real depth, however, and the first holograms were largely distortions in the film that contained a twin image, and so research was stymied until the invention of the pulsed-ruby laser in 1960. Those who had read Gabor's work and researched the theory recognised that laser was the ideal light source to produce and view holograms. One of the first three-dimensional holograms, now famous, was of a toy train and bird by Emmett Leith and Juris Upatniek in 1962 at the University of Michigan create using lasers.

By 1967 the first hologram of a person was made, and in the same year the first widely distributed hologram made it to the public in the 1967 World Book Encyclopaedia Science Yearbook, displaying a picture of chess pieces on a board.

And the rest is, as they say, well... bright.

Recent advances
Holography today is a refined science. Further advances in coherent light sources (continuous, monochromatic, single point and wavelength lasers, as opposed to pulsed lasers) as well as recording medium have seen holograms used just about everywhere - from various forms of art and creative expression to the more subdued uses such as on credit cards, mobile phone batteries, and those ugly Windows CDs and DVDs.

But what about storage? Research into holographic storage has actually been going on for over forty years, since the 1970s when computer scientists started worrying about the existing level of semiconductors and magnetic media being unable to meet the future memory and storage demands of computers. Of course, advances in precisely these areas relieved the pressure, but the idea of using holography to store data didn't die. The potential of the theory provides for some incredible volumes of storage, so the impetus has always been there, the problem - at least back then - was the technology to make it viable and affordable.

Today the ubiquity of consumer level devices like CDs and DVDs has created ubiquitous cheap lasers that could be ideal for use with holographic storage, which means all that's really missing now is the right recording medium and the mechanism to create the holograms.

Which is what GE's (General Electric) recent announcement on its holographic storage breakthrough was about. GE has a huge investment in chemical research and a base from which to produce suitable recording media, and combined with its technique of 'micro-holography' claimed that affordable holographic discs aren't too far off. The company isn't letting too much out about how the technology works, except the basic principle.

The general gist of all holographic media is this - why write on only one surface of the recording media (as with CD, DVD and Blu-ray), when you can write throughout the media itself? And essentially, the company is working on a form of 3D volumetric holographic storage with micro-holography using its own polycarbonate recordable media that can store holographic data in the substrate.

Logically, the thicker the disc the more room you have to store data, however GE is hoping a product developed on its technology would allow backwards compatibility with CD, DVD and Blu-ray products, meaning holographic discs are likely to use similar densities as current discs. Not that this is a bad thing - by GE's reckoning a DVD-sized disc of its holographic media could store 200 times the volume of data as current DVDs.

But there are competitors, and different approaches too. While GE isn't revealing much detail, a company called InPhase actually has tangible (though still young) products, have developed their own recording medium, and are even willing to show how it's done.

Here's the English translation...