A new state of light

05.05.2014 - A theoretical physicist has been able to explain how to capture particles of light at room temperature.

In doing so, Alex Kruchkov has confirmed the existence of a ‘new state of light’ which could pave the way for advanced computer chip, laser and solar panel technology

Previously, getting hold of these particles - called photons - was only thought to be possible under extremely cold temperatures. Light is made up of tiny quantum particles called photons. Physicists know that when quantum particles condense, they lose their individual identity. Their different energy levels collapse into a single macroscopic quantum state, causing them to behave like clones and form a ‘super particle’ or wave known as a Bose-Einstein condensate (BEC). This usually happens at extremely low temperatures of less than a micro-kelvin, or a millionth of a degree above absolute zero, according to a report by Katia Moskvitch on Live Science. Chilling rubidium atoms down to a low enough temperature in a compact space, for instance, causes them to quickly become indistinguishable, behaving like a single particle. A long-standing question in physics has been whether or not photons can be condensed like other quantum particles such as rubidium atoms. In theory it should work, but the main obstacle to proving the effect has always been that photons have no mass, which is a key requirement for a Bose-Einstein condensate. But in 2010, physicists from Bonn University in Germany were able to successfully condense photons in something known as a micro-cavity – a device made of two mirrored surfaces.The surfaces trapped a photon, which then behaved as if it had a mass.

However, up until now no one has been able to reproduce the experiment. ‘Understanding of the condensation of photons was like the light at the end of the tunnel,’ Mr Kruchkov, a doctoral student at the Swiss Federal Institute of Technology (EPFL), told Live Science. ‘Experimentalists were waiting for some simple but effective model, containing “a recipe” to “cook” light condensates. ‘I showed that the energy of light can be accumulated in the condensed state of photons,’ he said. Mr Kruchkov’s mathematical model shows that photons can be captured in a Bose-Einstein condensate state, and at room temperature and pressure. ‘Now, it is actually possible to predict the behaviour of the system for other experimental conditions. It also explains the temperature reaction of the experimental setup,’ he added. The research is important because a Bose-Einstein condensate of photons would represent a completely new state of light.‘In some sense, the BEC of light is a bridge between light and matter - the bridge unknown before,’ said physicist Sergiy Katrych, who was not involved in the study. This photonic Bose-Einstein condensate has characteristics resembling lasers, but with an important advantage.

‘We are currently not capable of producing lasers that generate very short-wave light – i.e. in the UV or X-ray range,’ explained Bonn University’s Jan Klärs. ‘With a photonic Bose-Einstein condensate this should, however, be possible.’For chip designers, this could mean that they could etch more detailed circuits in their semiconductor materials to create more powerful computers. Another possible application is to use the new state of light to power smaller solar cells that produce significantly more energy.

Originally by Daily Mail