"The ability to control light is a powerful one," said Professor Federico Capasso, from Harvard's School of Engineering and Applied Science. "Our understanding of optics on the macroscale has led to holograms, Google Glass and LEDs, just to name a few technologies. Nano-optics is a major part of the future of nanotechnology and this research furthers our ability to control and harness the power of light on the nanoscale."
Surface plasmons are confined to the surface of a metal. In order to create wakes through them, Prof Capasso's team designed a faster than light running wave of charge along a one dimensional metamaterial.
The metamaterial – a nanostructure of rotated slits etched into a gold film – changes the phase of the surface plasmons generated at each slit relative to each other, increasing the velocity of the running wave. The nanostructure also acts like a boat's rudder, allowing the wakes to be steered by controlling the speed of the running wave.
The team discovered that the angle of incidence of the light shining onto the metamaterial provides an additional measure of control and, by using polarised light, the direction of the wake can be reversed.
