Computing as we know it today is all thanks to one plucky little component: the transistor. This simple piece of technology, which is essentially an on/off switch that can be electronically controlled, is what has enabled the computing revolution of the last half century. However it has many well known limitations most of which stem from the fact that it’s an electrical device and is thus constrained by the speed of electricity. That speed is about 1/100th of that of light so there’s been a lot of research into building a computer that uses light instead of electricity. One of the main challenges that an optical computer has faced is storage as light is a rather tricky thing to pin down and the conversion process into electricity (so it can be stored in traditional memory structures) would negate many of the benefits. This might be set to change as researchers have developed a non-volatile storage platform based on phase-change materials.
The research comes out of the Karlsruhe Institute of Technology with collaborations from the universities of Münster, Oxford, and Exeter. The memory cell which they’ve developed can be written at speeds of up to 1GHz, impressive considering most current memory devices are limited to somewhere around a 1/5th of that. The actual memory cell itself is made up of phase-change material (a material that can shift between crystalline and amorphous states) Ge2Sb2Te5, or GST for short. When this material is exposed to a high-intensity light beam its state will shift. This state can then be read later on by using less intense light, allowing a data cell to be changed and erased.
One novel property that the researchers have discovered is that their cell is capable of storing data in more than just a binary format. You see the switch between amorphous and crystalline states isn’t distinct like it is with a transistor which essentially means that a single optical cell could store more data than a single electrical cell. Of course to use such cells with current binary architecture would mean that these cells would need a proper controller to do the translation but that’s not exactly a new idea in computing. For a completely optical computer however that might not be required but such an idea is still a way off from seeing a real world implementation.
The only thing that concerns me about this is the fact that it’s based on phase change materials. There’s been numerous devices based on them, most often in the realms of storage, which have purported to revolutionize the world of computing. However to date not one of them has managed to escape the lab and the technology has always been a couple years away. It’s not that they don’t work, they almost always do, more that they either can’t scale or producing them at volume proves to be prohibitively expensive. This light cell faces the unique challenge that a computing platform built for it currently doesn’t exist yet and I don’t think it can compete with traditional memory devices without it.
It is a great step forward however for the realm of light based computing. With quantum computing likely being decades or centuries away from becoming a reality and traditional computing facing more challenges than it ever has we must begin investigating alternatives. Light based computing is one of the most promising fields in my mind and it’s great to see progress when it’s been so hard to come by in the past.
