An Eigenanalysis Study of Tunable THz and Photonic Unbounded Structures Employing Finite Element Method

Abstract

This work aims at the establishment of a rigorous full-wave eigenmode analysis technique based on a finite element scheme for the study of terahertz (THz) or photonic/optical unbounded structures. This numerical tool follows the last decades' trend to migrate the technological knowledge from microwave to THz and photonic regimes. The performed eigenanalysis offers an insightful view of the studied structures, revealing their characteristics. For the truncation of the infinite solution domain, the first kind absorbing boundary conditions are employed, while the involved spurious modes are eliminated with the incorporation of a tree-cotree splitting formulation. The study focuses on tunable microring resonators supporting leaky-radiating wave propagation and bounded-resonating whispering gallery modes. Tunability is achieved by integrating an electro-optical layer and in turn through the enforcement of an external applied DC electric field. An innovative approach constitutes the numerical determination of the altered dielectric permittivity as a piecewise constant distribution rather than a constant mean value.

An Eigenmode Study of Nanoantennas from Terahertz to Optical Frequencies

“…Perfect electric conductors (PEC), S E , perfect magnetic conductors (PMC), S H , and the openradiating fictitious surface, S f i , where the ABCs are applied, comprise the domain boundary ∂Ω (namely, ∂Ω = S E S H S f i ). Although the utilized formulation is already given in our previous work [50], let us summarize this approach in the next section for a convenient and self-sustained paper.…”

“…In the first approach, an iterative process is introduced, the details of which can be found in our previous work [50]. For reasons of completeness, we only give here a brief description of this method.…”

“…The proposed formulation is based on our prior developed eigenvalue technique [50], which is appropriate for the study of any arbitrarily shaped geometry loaded with anisotropic and/or inhomogeneous materials. In what follows, the proposed formulation is demonstrated in Section 2; the penetration depth in metals is investigated in Section 3; and Section 4 cross-examines the results of published studies and those derived from a commercial simulator.…”