Magnetic mirrors are able to reflect light in ways old-fashioned mirrors can not, possibly leading to a new generation of technologies. Infrared wavelengths, slightly longer than those visible by the human eye, reflect off magnetic waves created by the new device.
Nanoscale antennas were placed in focal points of tiny magnetic reflectors. This energy was focused on the device due to absorption and emission of photons, similar to the way light reflects off atoms.
Light, including infrared frequencies, are forms of electromagnetic radiation. As the name suggests, this form of energy has both electrical and magnetic components. When it reflects off physical mirrors, both the image, as well as the electrical field, are reversed. This reversal of the electrical field has no effect on the image, as seen by the human eye. However, at the exact moment of reflection, waves cancel each other out, negating the electrical field of light at the surface of the mirror. This prevents tiny nanoscale antennas from functioning just above a physical reflector.
"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," Michael Sinclair of Sandia National Laboratories and co-author of a paper detailing development of the magnetic mirror, said.
Magnetic mirrors interact with the magnetic function of the wave, leaving electrical fields unaffected.
The base of the device is made of a non-magnetic material, which can be made to exhibit magnetic properties. The reason behind this is that no known metal reflects light through interactions with the magnetic field of electromagnetic radiation.
Photons, particles of light, have no charge, and can not normally be affected by magnetic fields. Development of metallic cells shaped like fish scales has allowed some reflection of photons, but the results were too inconsistent for use with nanoscale antennae.
Non-metallic dielectric resonators were the key to development of the new magnetic mirror. Tellurium, a metalloid element resembling tin, was used as the basis of the new device. The material is far more efficient than fish-scale devices at reflecting infrared waves. The new technology can also be manufactured using standard technology.
"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.
Magnetic mirrors could be used in new generations of lasers, solar cells, chemical sensors and more devices.
Development of magnetic mirrors was detailed in the journal Optica.