Plasmonic crystal alters to match light-frequency source

(Press-News.org) Contact information: Neal Singer
nsinger@sandia.gov
505-845-7078
DOE/Sandia National Laboratories
Plasmonic crystal alters to match light-frequency source A device like a photonic crystal, but smaller and tunable

ALBUQUERQUE, N.M. — Gems are known for the beauty of the light that passes through them. But it is the fixed atomic arrangements of these crystals that determine the light frequencies permitted passage.

Now a Sandia-led team has created a plasmonic, or plasma-containing, crystal that is tunable. The effect is achieved by adjusting a voltage applied to the plasma. Because the crystal then is agile in transmitting terahertz light at varying frequencies, it could increase the bandwidth of high-speed communication networks and generally enhance high-speed electronics.

"Our experiment is more than a curiosity precisely because our plasma resonances are widely tunable," says Sandia researcher Greg Dyer, co-primary investigator of a recently published online paper in Nature Photonics, expected in print in November. "Usually, electromagnetically induced transparencies in more widely known systems like atomic gases, photonic crystals and metamaterials require tuning a laser's frequencies to match a physical system. Here, we tune our system to match the radiation source. It's inverting the problem, in a sense."

Photonic crystals are artificially built to allow transmission of specific wavelengths. Metamaterials require micron- or nano-sized bumps to tailor interactions between manmade structures and light. The plasmonic crystal, with its ability to direct light like a photonic crystal, along with its sub-wavelength, metamaterial-like size, in effect hybridizes the two concepts. Its methods could be used to shrink the size of photonic crystals and to develop tunable metamaterials.

The crystal's electron plasma forms naturally at the interface of semiconductors with different band gaps. It sloshes between their atomically smooth boundaries that, properly aligned, form a crystal. Patterned metal electrodes allow its properties to be reconfigured, altering its light transmission range. In addition, defects intentionally mixed into the electron fluid allow light to be transmitted where the crystal is normally opaque.

However, this crystal won't be coveted for the beauty of its light. First, the crystal transmits in the terahertz spectrum, a frequency range invisible to the human eye. And scientists must tweak the crystal's two-dimensional electron gas to electronically vary its output frequencies, something casual crystal buyers probably won't be able to do.



INFORMATION:



The paper is titled "Induced transparency by coupling of Tamm and defect states in tunable terahertz plasmonic crystals."

Other authors are co-principal investigator Eric Shaner, Albert D. Grine, Don Bethke and John L. Reno, all from Sandia; Gregory R. Aizin of The City University of New York; and S. James Allen of the Institute for Terahertz Science and Technology at the University of California, Santa Barbara.

The work was supported by the Department of Energy's Office of Basic Energy Sciences (BES) and performed in part at the Center for Integrated Nanotechnologies, a Sandia/Los Alamos national laboratories user facility of DOE BES.

Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin company, for the U.S. Department of Energy's National Nuclear Security Administration. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major R&D responsibilities in national security, energy and environmental technologies and economic competitiveness.

Sandia news media contact:

Neal Singer
nsinger@sandia.gov
(505) 845-7078