Surface plasmons in noble metal films

The surface plasmons (SPs) guided by the films of noble metals have been modelled using the measured optical constants of Ag, Au and Cu. It is shown that Drude permittivity with the slowly varying plasma ωp(λ) and collision ν(λ) frequencies, retrieved from the experimental data, provides a comprehensive description of the main features of the guided SP modes and the SP resonances. The effects of dispersion and losses on the SP properties have been separated by scaling ν(λ) in the numerical analysis of the full-wave dispersion equation. Using Drude permittivity with the scaled ν(λ), it is demonstrated that in the absence of SP resonances, the ωp(λ) dispersion but not damping primarily determine the maximum attainable slow wave factor of SP. A detailed qualitative interpretation of the SP characteristics in the metallic films with the measured permittivity shed the light on the phenomenological mechanisms underlying the SP properties in the films of noble metals on dielectric substrates.