RESEARCHERS OBSERVE AND CONTROL LIGHT WAKES FOR THE FIRST TIME
(July 6, 2015) When a duck paddles across a pond or a supersonic plane flies through the sky, it leaves a wake in its path. Wakes occur whenever something is traveling through a medium faster than the waves it creates — in the duck’s case water waves, in the plane’s case shock waves, otherwise known as sonic booms.
Wakes can exist wherever there are waves, even if those waves are light. While nothing travels faster than the speed of light in a vacuum, light isn’t always in a vacuum. It is possible for something to move faster than the phase velocity of light in a medium or material and generate a wake. The most famous example of this is Cherenkov radiation, wakes produced as electrical charges travel through liquids faster than the phase velocity of light, emitting a glowing blue wake.
For the first time, Harvard researchers have created similar wakes of light-like waves moving on a metallic surface, called surface plasmons, and demonstrated that they can be controlled and steered. The discovery, published today in the journal Nature Nanotechnology, was made in the lab of Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at the Harvard John A. Paulson School of Engineering and Applied Science (SEAS).