Glide symmetry for mode control and significant suppression of coupling in dual-strip SSPP transmission lines

Xiao Tian Yan,Jun Feng Liu,Xin Xin Gao,Tie Jun Cui,Wenxuan Tang,Meng Wang

doi:10.1117/1.ap.3.2.026001

Abstract

Glide symmetry, which is one kind of higher symmetry, is introduced in a special type of plasmonic metamaterial, the transmission lines (TLs) of spoof surface plasmon polaritons (SSPPs), in order to control the dispersion characteristics and modal fields of the SSPPs. We show that the glide-symmetric TL presents merged pass bands and mode degeneracy, which lead to broad working bandwidth and extremely low coupling between neighboring TLs. Dual-conductor SSPP TLs with and without glide symmetry are arranged in parallel as two channels with very deep subwavelength separation (e.g., λ0 / 100 at 5 GHz) for the application of integrated circuits and systems. Mutual coupling between the hybrid channels is analyzed using coupled mode theory and characterized in terms of scattering parameters and near-field distributions. We demonstrate theoretically and experimentally that the hybrid TL array obtains significantly more suppressed crosstalk than the uniform array of two nonglide symmetric TLs. Hence, it is concluded that the glide symmetry can be adopted to flexibly design the propagation of SSPPs and benefit the development of highly compact plasmonic circuits.

Highlights

Surface plasmon polaritons (SPPs) are highly localized surface waves that exist on the interface of metal and dielectric beyond the far-infrared frequency
We introduce glide symmetry in the dual-strip spoof surface plasmon polaritons (SSPPs) transmission lines (TLs) to further improve the performance of plasmonic circuits
We introduce glide symmetry, which is a typical type of higher symmetry, to manipulate the dispersion characteristics of the SSPP structure

Summary

Introduction

Surface plasmon polaritons (SPPs) are highly localized surface waves that exist on the interface of metal and dielectric beyond the far-infrared frequency They do not naturally exist at lower frequencies such as terahertz and microwaves, where the metals no longer behave like plasma with negative dielectric constants.[1] In order to allow SPPs to operate in the lower frequency bands, spoof surface plasmon polaritons (SSPPs) have been conceived and realized on periodically structured metallic surfaces.[2] Similar to the optical SPPs, SSPPs exhibit highly localized electromagnetic (EM) fields, subwavelength resolution, and extraordinary field confinements.[3] ultrathin corrugated metallic strips have been proposed as. We introduce glide symmetry in dual-conductor SSPP TLs and TL arrays for characteristics control. Two SSPP TLs, one with glide symmetry and one without glide symmetry, are arranged in parallel as two channels with deep subwavelength separation (which is λ0∕100 at 5 GHz).

Glide Symmetry in Dual-Strip SSPP TLs

Hybrid Nonglide and Glide Symmetric TL Array

Near-Field Measurement

Conclusion