Research project could help create computers that run on light

In June Dr Fetah Benabid, of the Department of Physics at Bath, will lead a team of researchers to develop a new technique which would enable them to synthesise ‘waveforms’ using light photons with the same accuracy as electrons are used in electronics. Waveform synthesis is the ability to control very precisely the way that electric fields vary their energy.

Ordinarily, electric fields rise and fall in energy in a regular pattern similar to the troughs and crests of waves on the ocean, but modern electronics allows a close control over the shape of the ‘wave’ – in effect creating waves that are square or triangular or other shapes rather than curved.

It is this control of the variation of the electric field that allows electronic devices such as computers to function in the precise way needed.

But electronics has its limitations, and the development of ever smaller silicon chips which has allowed computers to double in memory size every 18 months or so will come to an end in the next few years because the laws of physics do not permit chips smaller than a certain size.

Instead, engineers are looking to the science of photonics, which uses light to convey information, as a much more powerful alternative. But so far photonics can use light whose waveform is in one shape only – a curve known as a sine wave – and this has limited value for the communications needed to run a computer, for example.

The Bath researchers want to allow photonics to create waveforms in a variety of different patterns. To do this, they are using the new photonic crystal fibres which are a great step forward in photonics because, unlike conventional optical fibres, they can channel light without losing much of its energy.

In the research, light of one wavelength will be passed down a photonic crystal fibre which then branches off in a tree-like arrangement of fibres, each with a slightly separate wavelength, creating a broad ‘comb-like’ spectrum of light from ultra-violet to the middle of the infra-red range.

...continued