Plasmonic lifetimes and propagation lengths in metallodielectric superlattices

Abstract

We study the complex plasmonic band structure of nanoscopically thin metallodielectric layers. It is shown that the lifetime and propagation lengths can be obtained with excellent accuracy using a perturbation technique, thus establishing a quantitative connection between mode dissipation and its electromagnetic fields. Ultimately, the perturbation approach is shown to elucidate the physical origin of the orders-of-magnitude variation of lifetime and propagation lengths across the band structure. The symmetrical Brillouin zone center mode is dissipated the least because its electric field is efficiently screened from the metal layers. For a typical silver--titanium dioxide system at visible and infrared frequencies, maximum lifetimes have been found in the subpicosecond and picosecond range, while the longest propagation lengths are direction dependent and in the 10 to 100-micron range. We have also shown that the ratio of the propagation length for a given direction and the lifetime is equal to the corresponding group velocity component.