By Cameron Chai
A research team at the Chalmers University of Technology have used two metallic nanoparticles to construct a nanoantenna, which can disperse red and blue colour lights in different directions.
The nanoantenna, which measures less than a light wavelength in size is comprises two metallic nanoparticles namely gold and silver. These nanoparticles, gold and silver were placed at a distance of 20 nm on a surface made of glass.
Ideally a nanoantenna, which is smaller than a light wavelength does not disperse light. But in this research it was discovered that the nanoantenna scattered light in order to disperse red and blue lights in different directions. This happened due to the optical phase shift created by the asymmetrical composition of materials said Timur Shegai. The optical phase shifts occurred due to the difference in Plasmon resonances. A Plasmon resonance happens when the electrons present in the nanoparticle oscillate according to the light frequency subsequently affecting the propagation of light inspite of the antenna being small.
Scientists have been able to establish that nanoantennas can be made to control the direction of the light through asymmetrical composition. They have also established that these antennas can be produced substantially over bigger areas using cost-effective colloidal lithography.
This phenomenon could also be used in optical nanosensors where the Plasmon can be used to construct sensors that can locate very low concentrations of bio molecules or gases. This can particularly help in diagnosing diseases at the initial stages to facilitate early treatment.
The research was funded by the Swedish Research Council, Goran Gustafsson Foundation and the Swedish Foundation for Strategic Research and the research findings were presented at the optical nanosensors international conference held at Chalmers University of Technology.