Dispersion Analysis of Twist-Symmetric Dielectric Waveguides

Pilar Castillo-Tapia,Oscar Quevedo-Teruel,Kwinten Van Gassen,Francisco Mesa,Zvonimir Sipus,Qiao Chen

doi:10.3390/photonics8060206

Pilar Castillo-Tapia, Oscar Quevedo-Teruel + Show 4 more

Open Access

https://doi.org/10.3390/photonics8060206

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Abstract

We propose a circular twist-symmetric dielectric waveguide that is polarization-selective. In the practical implementation of optical fibers, a selective circular polarization is more convenient than its linearly polarized counterpart where previous knowledge of the emitted polarization from the transmitter is unknown. The analysis of the waveguide was conducted with three methods: an eigenmode approach, simulation of a truncated structure, and the so-called multimodal transfer-matrix method (MMTMM). The presented simulations demonstrate that the operational band can be manipulated by tuning the parameters of the structure. Furthermore, the MMTMM allows for a direct and accurate calculation of the attenuation constant of the rejected circular polarization.

Highlights

The electromagnetic properties of periodic structures with higher symmetries were first studied in the 1960s and 1970s [1,2,3]
Two types of spatial higher symmetries can be found in the literature: glide and twist symmetry
The results provided by the eigenmode solver in CST reveal that, while the left-handed circularly-polarized (LCP) mode does not have a stop band in the first Brillouin zone, the right-handed (RCP) mode has a stopband between 6.4 and 7 GHz

Summary

Introduction

The electromagnetic properties of periodic structures with higher symmetries were first studied in the 1960s and 1970s [1,2,3]. Glide-symmetric structures have been demonstrated to exhibit lower dispersion and higher refractive indices than conventional structures [4], properties that are found useful when designing two-dimensional lens antennas [9,10,11,12]. Twist symmetry reduces the dispersion of periodic structures and increases its equivalent refractive index [23] These properties were experimentally demonstrated in coaxial lines [24,25] and hollow waveguides [26]. A similar feature was already proposed with the use of chiral fibers in [37] where a double helix was placed around a fiber This helix could be seen as an infinite-fold twist-symmetric structure [38]. Some results and relevant features of these three approaches are reported

Eigenmode Solver

Frequency Domain Simulation of a Truncated Structure

Conclusions