Tiny electrical waves now digitally controlled

Researchers from the FOM Institute AMOLF in Amsterdam and the University of Twente have developed a way to digitally control tiny electrical waves, so-called surface plasmons.

These waves play an important role in nanophotonic research, which studies materials at a very small scale. The new knowledge could lead to an interface that makes nanophotonic devices more user-friendly (comparable to Windows on a computer). The researchers published their results yesterday in the leading journal Nature Photonics.
When light reflects off gold nanostructures under the right conditions, it creates tiny electrical waves on the surface called surface plasmon polaritons (SPPs). The researchers have now achieved SPP control in a remarkably simple and universal manner. They did this by changing the shape of the incident light with a computer-controlled megapixel device called a phase plate (similar to a liquid crystal display).
Unlike previous approaches, phase plate control is cheap and highly flexible. The researchers demonstrated this flexibility by creating a sharply focused SPP spot and scanning it across a gold surface. Such a scanned focused spot could be used to create the first super-resolution SPP microscope. In addition, the method could result in new interfaces for nanophotonic devices. This would make them more accessible for industry.

Further information
Bergin Gjonaj, +31 (0)6 50 26 11 78.
 
Reference 
Active spatial control of plasmonic fields           
B. Gjonaj, J. Aulbach, P.M. Johnson, A.P. Mosk, L. Kuipers, A. Lagendijk
Nature Photonics (2011),doi:10.1038/nphoton.2011.57

Figure 1. Flexible control of the plasmonic waves using a pixelated phase plate (a) Light from each pixel of the phase plate acts as a source of plasmons on the gold film. The computer tunes the relative phases of the pixels, and thus of the plasmonic sources, to achieve constructive interference at a chosen spot. This creates a sharp plasmonic focus. (b) Relocation of the focus to a newly chosen spot. The position of the plasmonic focus is fully selectable from the computer.