Creating chaos to harvest light

Print edition : June 28, 2013

Distribution of light patterns of an optical cavity: non-chaotic (top) and chaotic.

AN international team of physicists has demonstrated that chaos can beat order, at least as far as light storage is concerned. The collaboration included researchers from the King Abdullah University of Science and Technology (KAUST), Saudi Arabia; the University of York, United Kingdom; the University of St. Andrews, Scotland; and the University of Bologna, Italy. The researchers deformed mirrors in order to disrupt the regular light path in an optical cavity and, surprisingly, the resulting chaotic light paths allowed more light to be stored than with ordered paths.

The work has important applications in fields like quantum optics and processing optical signals over the Internet. Solar cells may also benefit, as trapping more light in them improves their ability to generate electricity. The work will have other real-world practical applications as well. The research has been published in the journal Nature Photonics.

The work involved a study of optical cavities (resonators) and their ability to store light. Optical cavities typically store light by bouncing it many times between sets of suitable mirrors. The researchers demonstrated a six-fold increase of the energy stored inside a chaotic cavity as compared with a classical counterpart of the same volume.

“The concept behind broadband chaotic resonators for light harvesting applications is very profound and complex,” said Andrea Di Falco of the School of Physics and Astronomy, University of St. Andrews. The research was led by Andrea Fratalocchi from KAUST, Saudi Arabia, who also developed the theory behind chaotic energy harvesting.

“Chaos and disorder are ubiquitous phenomena that pervade our existence.… The majority of our systems try to avoid these effects, as we commonly assume that chaos diminishes the performance of existing devices. The focus of my research is to show that disorder can be used as a building block for a novel, low-cost and scalable technology that outperforms current systems by orders of magnitude,” Andrea Fratalocchi said.