Silver and gold films and fibers several nanometers thick: Very slow optical surface plasmons

On films and fibers of well-reflecting metals (silver, gold) several nanometers thick, surface plasmons could be slowed down by 10 to 40 times. The plasmons are additionally slowed down when the nanofilms (nanofibers) are placed into a medium with a dielectric constant that is approximately equal to but still smaller than the modulus of the negative dielectric constant of the metal. As the result, the optical frequency waves prove to have wavelengths of ∼4 nm, i.e., as in soft x-ray. The propagation losses of these waves are moderately high. We propose to develop the optics (the optical transformations — deviation, focusing, photonic crystals, etc.) of these waves on thin metal layers integrated into nanodevices. In particular, we calculated the probability of spontaneous emission of a photon by an atom (molecule) into the surface plasmon of a nanoparticle. This probability proved to be increased by many orders of magnitude. This work interprets experiments that show a higher (14 orders of magnitude and more) probability of spontaneous Raman scattering of a molecule on the surface of a silver nanoparticle. The molecule is in the field of a surface plasmon, owing to which the local field and density of states of the field prove to be increased to such an extent as to give a rise of 12 or 13 orders of magnitude. An additional increase by one or two orders of magnitude is due to the antenna effect of a pair of nanoparticles, one of which is extremely small and the other is sufficiently large to serve as an efficient transceiver antenna. The possibility of developing sources of light pulses of exceptionally short duration arises.