Near-field optical phase antennas for long-range plasmon coupling.

Plasmon-mediated long-range coupling of optical excitations is shown to be attainable using near-field phase antennas involving nanoparticles situated at focal spots. The antennas rely on metal-surface features that are geometrically arranged to produce constructive interference of plasmons emanating from a source spot over a designated image position. Large image-field intensities and focal spots as narrow as one-third of the wavelength are obtained for source-image separations of tens of micrometers. The ability to strongly couple distant focal spots through phase accumulation produced by engineered plasmon scatterers opens up a vast range of possibilities in contactless plasmon sensing, optical interconnects, and microscopy.