Light can be guided and manipulated at the nanometre scale by passing it through collections of tiny metal spheres -- according to new calculations by scientists in the US. The effect involves the interaction of light with plasmons on the surfaces of the spheres and the researchers claim that it could be used to create sources of coherent and polarized light. Such sources could be important for making a variety of all-optical nanodevices including sensors, switches and information storage devices ( J. Phys. B: At. Mol. Opt. Phys. 40 S283).
Plasmons are “quasiparticles” that describe the collective oscillations of electrons on the surfaces of metals. Plasmons interact with light and researchers are trying to exploit this property in “plasmonic” devices for processing and transmitting data.
Now, Maxim Sukharev and Tamar Seideman of Northwestern University have used a computer simulation to study the interaction between light and the plasmons on the surfaces of tiny metal spheres. Using the example of a T-junction composed of silver nanospheres, the simulation revealed that the path taken by the light through the spheres could be altered by changing the polarization of the light. The researchers believe that this effect – which has yet to be confirmed experimentally — could be used in an optical nanoswitch, or inverter.
The calculations also suggested that incident light can be confined within “plasmonic crystals” made from periodic arrays of nanoparticles. Moreover, depending on the geometry of the crystal, the light could be focused and guided. In addition, the computer results suggested that the effect could be harnessed in nanoscale light sources with controllable coherence and polarization properties.
The researchers believe that their modelling techniques could offer a practical way to predict the optical responses of plasmonic devices during the design process.
