Very slow surface plasmons: Theory and practice (Review)

The theory and practical applications of very slow (antisymmetric) optical plasmons are described. These plasmons can exist on thin metal films and filaments and (as standing waves) on metal spheres and ellipsoids. The material presented here extends the conventional concepts of electromagnetic modes of spaces, probability of spontaneous emission, construction of optical images, optical focusing, and the photon momentum. The reviewed achievements in this field have been obtained in the last years. The problem of the photon momentum in a medium has been a subject of irreconcilable disputes for nearly 100 years, beginning with Minkowski and Abraham's famous papers. Various practical applications are considered, including experiments with the significant enhancement of atom spontaneous emission into a plasmon field mode of a nanoparticle; experiments on focusing optical radiation into a spot much smaller than the diffraction-limited one (the so-called almost ideal Pendry lens, which produces an image with details much smaller than the light wavelength); and, finally, a greatly increased (by factors of 10, 100, or more) photon momentum in plasmon.