Abstract:

An equivalent circuit (EC) FDTD method is derived, first for the case of non-dispersive materials and next for the case of dispersive materials. In the later case, both an extended-Drude and a combined Drude/1-pole Lorentz permittivity function, with corresponding circuit (admittance) models, are proposed and shown to perfectly agree with experimental data over a wide range of frequencies, with a broader frequency range of validity for the second model. A novel optical nano-coupler based on surface plasmon (SP) coupling between two metal-dielectric interfaces of a metal (Ag) slab embedded in a dielectric material (SiO2) is proposed, analyzed with the EC FDTD method, characterized in terms of scattering parameters and fields distributions, and shown to provide several operation modes, including power splitter and diplexer. The structure features super-compact size (around 2 µm) and low-loss (0.4 dB at 769 nm for power splitting operation, and 1.4 dB and 2.4 dB for the diplexing of light waves in 633 nm and 533 nm bands), and may therefore find various applications.