Credit: Image courtesy of Hess et al. Nano Lett. 15, 3472-3478 (2015). Copyright 2015 American Chemical Society
Specially designed, extremely small metal structures can trap light. Once trapped, the light becomes a confined wave known as a surface plasmon. The plasmons propagate from the source to locations several hundred microns away, almost as fast as light through the air. Here the surface plasmons are represented by the blue waves, which begin at the pump beam and are detected hundreds of microns away by the probe beam.