Abstract
Mode properties of circularly symmetric waveguides with one special type of bianisotropy are studied using finite element approach. We find that the polarization degeneracy in circularly symmetric waveguides can be eliminated, by introducing intrinsic crossing coupling between electric and magnetic moments in the constituent units of the waveguide media. Breaking the polarization degeneracy in high order mode groups is also confirmed numerically. With the bianisotropic parameters chosen in this work, the x and y-polarized modes remain decoupled. Typically, the y-polarized modes remain completely unchanged, while the x-polarized modes are turned into leaky modes that are lossy along propagation direction. A perturbation model from coupled mode theory is developed to explain the results and shows excellent agreement. Such asymmetric behavior between different polarizations might be feasible and useful for developing compact polarizers in terahertz or mid-infrared regime.
Highlights
In metamaterials, the most general description of material properties is bianisotropic constitutive relation, which governs material responses to the electromagnetic (EM) fields, as well as the cross terms, i.e., magnetic dipoles induced by the incident electric fields
It was found that most of moving media are bianisotropic by Kong [3, 4], who invented the concept of bianisotropy to describe the electromagnetic properties of such kind of materials
Chirowaveguides proposed by Engheta are realized by filling cylindrical waveguides with isotropic chiral media, while chiral fibers are experimentally feasible with current fiber technology, i.e., by microforming glasses or decorating glass surfaces to create helical structures
Summary
The most general description of material properties is bianisotropic constitutive relation, which governs material responses to the electromagnetic (EM) fields, as well as the cross terms, i.e., magnetic (electric) dipoles induced by the incident electric (magnetic) fields. Chirowaveguides proposed by Engheta are realized by filling cylindrical waveguides with isotropic chiral media, while chiral fibers are experimentally feasible with current fiber technology, i.e., by microforming glasses or decorating glass surfaces to create helical structures. We note that in all the aforementioned work, the chiral media are isotropic As for light, it corresponds to a macroscopic model where chiral molecules are randomly distributed in the host, while for microwave the counterpart is the wire helices with random orientations in the host media. We extend the aforementioned work on chirowaveguides to the regime where the media can be bianisotropic using a finite element approach.
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