Trapped rainbow

1 min read

A technique developed by the University of Surrey and Salford University may be able to slow, stop and capture light. The approach may be applicable to data storage as well as in optical networks.

The research has been undertaken by Professor Ortwin Hess and PhD student Kosmas Tsakmakidis of the Advanced Technology Institute and Department of Physics at the University of Surrey, and Professor Alan Boardman from Salford University. The technique uses light, rather than electrons, as a memory. Because light has a broad spectrum, it may increase storage capacities by a factor of 10. ‘Slow light’ may also increase the speed of optical networks, with some data packets slowed at interconnections to let others through. According to the researchers, previous attempts to slow and capture light have involved cryogenic temperatures, have been costly and have only worked with one specific frequency of light. The technique being proposed involves negative refractive index metamaterials, along with the exploitation of the Goos Hänchen effect. This shows that, when light hits an object or an interface between two media, it does not bounce back immediately, but seems to travel very slightly along that object, or in the case of metamaterials, travels very slightly backwards along the object. Professor Hess’ theory shows that, if you create a tapered layer of glass surrounded by two suitable layers of negative refractive index metamaterials, a packet of white light injected into this prism from the wide end will be completely stopped at some point in the prism. As different component ‘colours’ of white light have different frequencies, each frequency would therefore be stopped at a different stage down the taper, creating a ‘trapped rainbow’. Professor Hess said: “Our ‘trapped rainbow’ bridges the exciting fields of metamaterials with slow light research. It may open the way to the long awaited realisation of an optical capacitor.”