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 PCs many times over to be possible, 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), led by Dr Siyuan Yu, Reader in Photonics and Optical Communications at Bristol University’s Department of Electrical and Electronic Engineering, will develop integrated optical logic and memory devices based on a semiconductor ring laser (SRL).
The team 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 does not appear to be very sensitive to temperature and works in a wide range of operational conditions. What is more, it is suitable for miniaturisation - key to making a lot of it on a single semiconductor chip.
Dr Siyuan Yu, commenting on the project, said: “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 to create an all-optical information processing system.
“Such a system has been the 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.”