Terahertz surface plasmon propagation in a near field coupled asymmetric resonators based planar waveguide

Abstract

In this article, we investigate terahertz surface plasmons propagation in a planar waveguide comprising asymmetric resonators placed in close proximity. The waveguide is designed to support surface plasmon polaritons at two distinct terahertz frequencies, ω 1 and ω 2, which are near to each other. This is accomplished by carefully designing the unit cell comprising of two resonators with slightly different sizes. The resonators in the form of rectangular apertures are placed along the transverse direction in the near field regime. We observe an absorption window surrounded by two transmission resonances which are coupled to each other. As the resonators are moved apart, we observe a switching from the coupled to an uncoupled resonance state. The absorption window can be tuned by changing the resonance frequency of the resonators, which depends upon its structural parameters. We have employed a theoretical model to understand the coupling mechanism between the resonators and the dispersive behavior resulting in the absorption window. The proposed study is significant in the construction of planar terahertz components such as slow lights systems, buffers, etc, where strongly dispersive mediums play a vital role.