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  • Magnetic Mirror Reflects Light in New Ways

Photonics.com
Oct 2014
ALBUQUERQUE, N.M., Oct. 16, 2014 — A new magnetic mirror uses non-metallic metamaterial properties to reflect IR light.

Scientists at Sandia National Laboratories developed the magnetic mirror by placing nanoscale antennas at or very near the mirror’s surface, thereby allowing the researchers to harness IR radiation. At optical frequencies, the magnetic properties required for strong interaction can be achieved only by using artificially tailored materials, the researchers wrote in the study.


The cubic dielectric resonators on the left side act as a dielectric magnetic mirror in the optical frequency range. In contrast, the gold surface on the right side exhibits a 180-degree phase shift of the electric field upon reflection. Courtesy of OSA.

They developed a 2-D array of dielectric nanoscale resonators using tellurium, which has a lower signal loss than metals. The cube-shaped resonators are considerably smaller than the IR wavelengths, which makes the new design reflective and creates a strong electrical field at the mirror’s surface.

The resonators were also found to strongly interact with the magnetic component of incoming light. Reflective properties of the resonators emerged because they behaved like artificial atoms, absorbing and then re-emitting photons in random directions.

“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,” said Sandia scientist Dr. Michael Sinclair.

Conventional mirrors reflect IR light by interacting with its electrical component. They not only reverse the image, they also reverse the light’s electrical field. The new magnetic mirrors reflect IR light by interacting with their magnetic field, preserving their original electrical properties.

“A magnetic mirror … produces a very strong electric field at the mirror surface, enabling maximum absorption of the electromagnetic wave energy,” said Sandia scientist Dr. Igal Brener.

The researchers used time-domain spectroscopy to ensure that the new design would continue to behave like a true magnetic mirror and not reverse the phase of light upon reflection.

“Our results clearly indicated that there was no phase reversal of the light,” said Sheng Liu, a postdoctoral associate at Sandia. “This was the ultimate demonstration that this patterned surface behaves like an optical magnetic mirror.”

The scientists are investigating other materials to demonstrate magnetic mirror behavior at even shorter optical wavelengths. This could potentially enable the development of smaller lasers, as well as photodetectors, solar cells and other optical systems. The research was published in Optica.

For more information, visit www.sandia.gov.


GLOSSARY
reflection
Return of radiation by a surface, without change in wavelength. The reflection may be specular, from a smooth surface; diffuse, from a rough surface or from within the specimen; or mixed, a combination of the two.  
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