Frequency and time domain analysis of cavity plasmon waveguides

In the present contribution we propose and analyze a specific design cavity plasmon waveguide, consisting of spheroidal silicon nanoparticles in gold, which ensures single-mode operation at visible frequencies and can be realized in the laboratory using modern nanofabrication techniques. The plasmon modes of the cavities correspond to complex eigenfrequencies because of absorptive losses in the metallic material. We discuss the possibility of compensating for these losses by infiltrating the silicon nanoparticles with active centers, which are capable of sustaining an inversion of population under excitation by light of a different wavelength or by electric discharge. Our results are analyzed, also, in the light of a simple tight-binding model, which enables physical insight. The model becomes more accurate as the interparticle separation increases. Finally, we study the response of the above waveguide under time varying excitations by a localized light source. Specifically, starting from the time-depended Maxwell equations, we obtain a system of differential equations in a tight-binding form and discuss spatio-temporal solutions of these equations for specific types of excitation.