German Physicists Transmit Optical Signal on the Nanoscale
6 December 2013
Scientists at the University of Wurzburg, Germany, have achieved a major breakthrough in the field of nano-optics, finding a way to control the movement of individual light particles on computer chips and nanostructures and setting the stage for the development of optical circuits.
Two teams of physicists, led by Professor Bert Hecht and Professor Tobias Brixner, managed to feed a light signal through an antenna into a waveguide, confining it to emit at the other end through a second antenna. The experiment was successful as the transmission of the optical signal occurred in small structures that could be incorporated into contemporary microelectronics. It's also important to note that the antennas and the waveguide measured just a few hundred nanometers.
In general it's hard to control photons at such a small scale, which makes combining photonic technologies with silicon-based technology of conventional computer chips even more challenging, according to Hecht. The researchers, however, managed to find a way to control them, working with bound photons, rather than free photons, which form on the surface of highly-conducting materials such as gold. Incident light can produce there certain electron oscillations, also called plasmons, which propagate along the metal to release light elsewhere. The behavior of plasmons resembles that of free photons, with the difference that they can be concentrated into very small places.
In the journal Physical Review Letters the researchers recently presented the first-ever simple plasmonic circuit, comprised of an antenna around 200 nanometers long that has the capacity to capture free photons and turn them into plasmons. The antenna is bound to a plasmon waveguide that consists of two fine gold wires, which have a length of three micrometers and are placed parallel to each other, allowing for the charge waves to spread in two defined patterns. This approach could be applied in future for controlling the movement of plasmons, something that cannot be achieved with electrons.