Spoof Surface Plasmon Polariton Beam Splitter

Propagation of terahertz (THz) wave utilizing spoof surface plasmon polariton (SSPP) earned a great deal of attention due to the ability of SSPP modes to guide THz waves at very low dispersion. We present an investigation of the SSPP beam splitter, one of the key elements of many optical setups. In contrast with conventional free space implementations, in the case of the SSPP beam splitter, one can no longer disregard scattering of incoming wave back into the input channels. Thus, SSPP implementations must take into consideration both the splitting ratio and the backscattering as important parameters characterizing the beam splitter. Three different designs representing different approaches to solving the problem of the relation between these parameters are investigated. The mathematical formalism to study the dispersion diagrams is proposed. The frequency dependence of splitting ratio, scattering parameters, and backscattering for each beam splitter is investigated. Finally, by employing one of the proposed beam splitter, a controllable filter is designed and analyzed.