Light source discovery challenges basic assumption of physics

A widely-held understanding of electromagnetic radiation has been challenged in a newly published research which found that normal direct correspondence between the bandwidths of the light source and emitted radiation can be broken.
The study by the University of Strathclyde in the UK found that the normal direct correspondence between the bandwidths of the current source and emitted radiation can be broken.
This was achieved by extracting narrowband radiation with high efficiency, without making the oscillation of the current narrowband.
The finding produced narrowband light sources in media where electromagnetic radiation would not normally be possible.
It makes for a powerful tool for scientists that enables them to understand the intricacies of how materials, or even biological molecules, behave under different conditions, which has a major impact on people's lives through the development of new products and medical treatments.

The research, published in Scientific Reports, also involved researchers at the Ulsan National Institute of Science and Technology (UNIST) and the Gwangju Institute of Science and Technology (GIST), both in South Korea.

Professor Dino Jaroszynski, of Strathclyde's Department of Physics who led the study said: "Coherent light sources such as lasers have many uses, from communication to probing the structure of matter. The simplest source of coherent electromagnetic radiation is an oscillating electric current in an antenna".
However, there are many other devices are based on these basic laws of physics, such as the free-electron laser, which produces coherent X-ray radiation, or magnetrons found in microwave ovens.

"Our study has shown that some common media with interesting optical properties can be taken advantage of if we imbed, or bury, an oscillating current source in them," Dino said.
"Media such as plasma, semiconductors and photonic structures have a 'cut-off', where propagation of electromagnetic radiation with frequencies lower than the 'cut-off' frequency is not possible.We noticed that the radiation impedance is increased at the cut-off," he added.
"One consequence of this is that, for a broadband current source immersed in this type of dispersive medium, the cut-off frequency 'mode' is selectively enhanced due to Ohm's law, resulting in narrow bandwidth emission," he said.

Professor Min Sup Hur at UNIST, Republic of South Korea, who leads the work from UNIST, said: "This new discovery is scientifically interesting, because it leads us to see the phenomenon of electromagnetic radiation from a completely different viewpoint.