New discovery challenges physics assumption

The production of narrowband light sources - where electromagnetic radiation would not normally be possible - has been achieved by scientists in Scotland.

The scientist’s achievement challenges a widely held quality of electromagnetic radiation and could be essential for cutting-edge science.

Professor Dino Jaroszynski, from Strathclyde’s Department of Physics, who led the study, said: “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.”

In the study, researchers achieved this by breaking normal direct correspondence between the bandwidths of the current source and the emitting radiation, something thought unachievable. This research could provide a way for scientists to understand the intricacies of how materials or biological molecules behave under different conditions, influencing research of new products or medical treatments.

Electromagnetic sources used as scientific tools require good coherency, monochromaticity and high emission power. Coherence and monochromaticity – or narrow bandwidth – allows the use of electromagnetic radiation to observe changes in the structure of materials.

Media such as plasma, semiconductors and photonic structures have a ‘cut-off’, where propagation of electromagnetic radiation with frequencies lower than a certain frequency is not possible; and the researchers noticed that the impedance increased at the cut-off.

Professor Jaroszynski said: “What is curious is that novel physics should still be hidden in the classical cut-off behaviour; in our research, we uncovered a hidden face of the cut-off and realised a new paradigm of narrowband light sources in media that would not usually allow electromagnetic radiation to propagate. This is a remarkably simple idea based on straightforward physics theory that seems to have been overlooked.”

The main challenge facing researchers currently is making high electromagnetic radiation sources monochromatic. An inefficient method of obtaining this is by making the oscillating current narrowband or by filtering the spectrum -however this is complicated and can be expensive.

Professor Min Sup Hur at Ulsan National Institute of Science and Technology (UNIST), who led the study there, said: “This new discovery is scientifically interesting, because it leads us to see the phenomenon of electromagnetic radiation from a completely different viewpoint."

This research was the result of collaboration between the University of Strathclyde, UNIST and the Gwangju Institute of Science and Technology, both based in South Korea.

The study was published in Scientific Reports.