Oldenburg physicists track light storage in real time

Oldenburg. The idea of capturing and storing light has fascinated researchers for centuries. The complexity lies in the enormous speed of light: it only takes a second to travel from the earth to the moon. In nanostructures, solar cells for example, it only lasts a few femtoseconds - that's the cheapest part of a second. A German-Japanese research team led by Prof. Dr Christoph Lienau, physicist at the University of Oldenburg, has now succeeded in tracking the trapping - physicists call it localisation - of light in artificial nanostructures in real time. In the May issue of the renowned journal Nature Photonics, the Oldenburg physicists, in close collaboration with scientists from the Universities of Tokyo and Ilmenau, show for the first time how long light can be stored in a random arrangement of tiny needles made of zinc oxide.

"You can imagine these needles as a maze for light: Once light rays have entered, they have trouble finding their way out again," explains Oldenburg physicist Martin Silies, who coordinated the experiment. In order to track down the light, the scientists have developed a new microscope with extremely high time resolution. The key trick is to couple light pulses into the zinc oxide structure that are shorter than its storage time, explains Silies. "This allows us to directly measure how long the localisation lasts."

The findings can be applied in many ways. "We expect, for example, that solar cells can be improved if it is possible to store the sunlight entering them for longer," explains Lienau. "Our experiments show how this light storage works in detail - and this understanding will help us to make light storage even more efficient."

The new results are just the beginning. The collaboration between the research groups from Oldenburg, Ilmenau and Tokyo, funded by the German Research Foundation (DFG) and the Japan Science and Technology Agency, has worked extremely well, says Lienau. "We will continue it and hope that our work will not only lead to the improvement of solar cells, but also to the development of completely new nanolasers."

[Press release from 16.04.2012]