A never-before-seen class of mirrors allows researchers to capture electromagnetic radiation, which could lead to advances in chemical sensors, solar cells, lasers, and optoelectronic devices.
The innovation works by reflecting infrared light using the magnetic properties of a non-metallic metamaterial. Nanoscale antennas placed at the surface of these "magnetic mirrors" allow them to capture the radiation, The Optical Society reported.
"We have achieved a new milestone in magnetic mirror technology by experimentally demonstrating this remarkable behavior of light at infrared wavelengths. Our breakthrough comes from using a specially engineered, non-metallic surface studded with nanoscale resonators," said Michael Sinclair, co-author on the Optica paper and a scientist at Sandia National Laboratories in Albuquerque, New Mexico, USA who co-led a research team with fellow author and Sandia scientist Igal Brener.
The cube-shaped resonators employ the element tellurium and are even smaller than the width of a human hair and thinner than the waves of infrared light.
"The size and shape of the resonators are critical, as are their magnetic and electrical properties, all of which allow them to interact uniquely with light, scattering it across a specific range of wavelengths to produce a magnetic mirror effect," Sinclair said.
Conventional mirrors reflect light by interacting with the electrical components of radiation, but to confirm the new magnetic device was actually behaving like a mirror the researchers needed to measure how light waves overlap as the bounced off the mirror's surface and overlapped. Since normal mirrors reverse this phase of light, evidence that the phase signature of the wave was not reversed would be proof the new device was working.
To make this detection the researchers used a technique called time-domain spectroscopy, which is used to measure phase at longer terahertz wavelengths. Very few scientists have successfully used this technique at shorter wavelengths, as was done in this experiment.
"Our results clearly indicated that there was no phase reversal of the light," remarked Sheng Liu, Sandia postdoctoral associate and lead author on the Optica paper. "This was the ultimate demonstration that this patterned surface behaves like an optical magnetic mirror."
In the future the researchers hope to look into how other materials can also demonstrate magnetic mirror behavior at even shorter wavelengths.
"If efficient magnetic mirrors could be scaled to even shorter wavelengths, then they could enable smaller photodetectors, solar cells, and possibly lasers," Liu concluded.
