Nanoplasmonic Directional Coupler Using Asymmetric Parallel Coupled MIM Waveguides

This article presents the design and analysis of a nanoplasmonic directional coupler using an asymmetric parallel-coupled line metal insulator metal (MIM) waveguide. The proposed plasmonic directional coupler is designed by applying three wire transmission line (TL) model based on the basic TL characteristic parameters of the related asymmetric parallel coupled line structures. To this end, the effective refractive index, propagation length, and characteristic impedance of the related coupled line MIM waveguide structure are obtained by using fullwave simulation software CST microwave studio suite. Specifically, the dual-band nature can be obtained by exchanging the asymmetric coupled line MIM waveguide section with two asymmetric even mode step impedance resonators (SIRs) by adjusting the gap width (g
₁
). Subsequently, a side-coupled resonator is designed and analyzed. Hence, the designed coupler is more useful to exchange several plasmonic devices such as power splitters and mixers in photonic integrated circuits (PICs) at a subwavelength scale.