Timur Shegai and co-workers, Chalmers University of Technology, Gothenburg, Sweden, have built a nanoantenna that directs red and blue light in opposite directions. The antenna is smaller than the wavelength of visible light, 390–770 nm, so should not be able to scatter light. An optical phase shift was created through an asymmetric material composition. For this, two nanoparticles, one silver and one gold, were placed 20 nm apart on a glass substrate. The difference in permittivity between gold and silver created the optical phase shift in the blue region of the spectrum which scattered the light in different directions.
Dense assemblies of these bimetallic color routers can be fabricated over large areas using cheap colloidal lithography which should facilitate their application to optical sensor development, spectroscopy and photonics.
This work shows that light can not only be manipulated by plasmon resonance and device geometry, but also by material composition.
- A bimetallic nanoantenna for directional colour routing
T. Shegai, S. Chen, V. D. Miljković, G. Zengin, P. Johansson, M. Käll,
Nat. Commun. 2011, 2, 481.