A nanoscale game of "now you see it, now you don't" may contribute to the creation of metamaterials with useful optical properties that can be actively controlled, according to scientists at Rice University.
A Rice laboratory led by chemist Stephan Link has discovered a way to use liquid crystals to control light scattered from gold nanorods. The researchers use voltage to sensitively manipulate the alignment of liquid crystal molecules that alternately block and reveal light from the particles; the gold nanorods collect and retransmit light in a specific direction.
The research was reported in the American Chemical Society journal Nano Letters.
It seems simple, but Link said the technique took two years to refine to the point where light from the nanoparticles could be completely controlled.
"The key to our approach is the in-plane rotation of liquid crystal molecules covering individual gold nanorods that act as optical antennas," said Link, an assistant professor of chemistry and electrical and computer engineering. "Learning how our devices work was exciting and has provided us with many ideas of how to manipulate light at the nanoscale."
Link said the device is actually a super half wave plate, a refined version of a standard device that alters the polarization of light.
With the new device, the team expects to be able to control light from any nanostructure that scatters, absorbs or emits light, even quantum dots or carbon nanotubes. "The light only has to be polarized for this to work," said Link, who studies the plasmonic properties of nanoparticles and recently authored a perspective on his group's recent research in plasmonics for the Journal of Physical Chemistry Letters. (View a video of Link and his team here.)
In polarized light, like sunlight reflecting off water, the light's waves are aligned in a particular plane. By changing the direction of their alignment, liquid crystal
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