Plasmon microscope with super-resolution

Plasmons are essentially electromagnetic modes that can arise and propagate on a metal surface. Much as a photon is a localized manifestation of a free-space EM field, a surface plasmon polariton (SPP) is a localized excitation in a plasmon field. Last year, Igor Smolyaninov of the University of Maryland and his colleagues demonstrated a far-field light microscope, based on SPPs traveling on a glycerine-wetted gold film, that could achieve a resolution better than 100 nm. As reported at the March 2006 meeting of the American Physical Society, the researchers have improved the device’s resolution to about 60 nm by nanopatterning the gold film, much like a photonic crystal. They then used digital image-processing techniques to approach 30-nm resolution. The SPPs were excited with light of about 515 nm. Shown here is a C-shaped hole imaged on the left with a scanning electron microscope and on the right with an SPP-assisted...