Examining the theoretical basis for the analysis of surface plasmons in the microwave and terahertz regimes

Surface electromagnetic modes guided by thin metal layers are usually called surface plasmons SP. SP were originally discovered by Ritchie in the fifties of the twentieth century in the optical regime. Then, surface plasmons found many applications in different areas of science including terahertz and microwave devices. Departing from optics to radio frequencies, an urgent need for a solid theoretical basis to analyze SP in those regimes has appeared. The only candidate was Sommerfeld´s analysis for radiation of electromagnetic waves over imperfect ground planes, published in 1909. This kind of analysis has been used recently by many researches working on SP applications at radio frequencies. The main goal of this paper is to give a theoretical analysis which proves the unsuitability of Sommerfeld´s analysis to the problem of SP.