An optical computer could be only light years away

One of science's longest wanted devices, an 'optical memory' that can store digital information as light in a way similar to how memory chips in PCs store information could not be so many light years away thanks to funding of over タ1 million by the European Commission.

It is well known that light can carry a lot more information than an electric current. For an optical computer that would outpace today's PC many times over a form of memory using light is needed to store information. The problem is light never stops.

The IOLOS project (Integrated optical logic and memory using ultra-fast micro-ring bistable semiconductor lasers) will develop integrated optical logic and memory devices based on a device called semiconductor ring laser (SRL).

The team, including Marc Sorel from the University of Glasgow's Department of Electronics and Electrical Engineering, will work on the principle that light will encircle a SRL in one of the two possible rotational (clockwise or counter clockwise) directions therefore emitting a laser beam in only one of the two directions. When looking at output from one direction, you would either see 'light' or 'dark', representing '0' or '1' in a digital system in optical form.

Provided energy is supplied to the device, the recirculation is endless, much like a toy racing car going around its track for as long as the battery has power. The device can therefore remember its state as long as power supply to the SRL is not interrupted. To set the direction of the recirculation, a beam of light needs to be launched in that direction to begin with, very much like writing a '1' or '0' into a computer memory.

Many other types of potential devices have been tried before, but the SRL seems particularly robust in that it doesn't appear to be very sensitive to temperature and works in a wide range of operational conditions. What's more, it is suitable for miniaturisation - key to making a lot of it on a single semiconductor chip.

Marc Sorel from the University of Glasgow's Department of Electronics and Electrical Engineering, said: "Glasgow's contribution to the project is based on our state-of-the-art capability for making very small structures with exceptional precision - using the recently inaugurated James Watt Nanofabrication Centre."

Dr Siyuan Yu from the University of Bristol added: "By making the SRL really small, we aim to develop a practical technology that may one day provide optical memories operating just like electronic memories.

"This work is still in a preliminary stage but the understanding and expertise in the consortium over SRL-related physics is very strong due to the accumulation of several years' research in this area. Although this is a very challenging undertaking, all the indications point to a very promising technology that would provide a key missing link in the endeavor towards an all-optical information processing system.

"Such a system has been subject of worldwide research for many years, and would boost the capacity of information systems significantly by dealing with information in the form of photons instead of converting it into electronic form."

Kate Richardson (

For more information please contact the University of Glasgow Media Relations Office on 0141 330 3683 or email

First published: 2 November 2006