Long-Range Spoof Surface Plasmons(LRSSP) on the Asymmetric Double Metal Gratings

Yong-Qiang Liu,Liangsheng Li,Hongcheng Yin

doi:10.1109/jphot.2021.3070880

Abstract

Spoof surface plasmons (SSP) on the corrugated metal surfaces have been widely studied over the past decade in both microwave and Terahertz (THz) band. Previous studies show that SSP mode on the metal grating suffers from high dissipative losses in high THz band especially near asymptotic frequency which may limit its real applications. The issue can be addressed by utilizing long-range SSP mode (LRSSP). LRSSP is a special low-loss symmetric propagating surface wave mode along double-layer corrugated metallic waveguides. In this paper, the asymmetric double metal gratings are proposed to support LRSSP which can significantly reduce the damping losses of the other short-range SSP mode (SRSSP) on the conventional doubly-corrugated metallic surfaces, thus enabling new possibilities to utilizing this SRSSP mode within long-range manner. According to our dispersion theory and the numerical calculations, the propagation loss of LRSSP is still lower than that of SRSSP within asymmetric regime, which demonstrates good tolerance to the asymmetry of the double-layer corrugated structure. However, its long-range propagation superiority of LRSSP vanishes gradually as the degree of asymmetry is enlarged. This work provides an alternative approach to increase the propagation length of SRSSP mode on the doubly-corrugated metallic surfaces and can open up new avenues to develop some novel LRSSP-based plasmonic devices such as waveguides, filters, sensors and active powerful radiation sources induced by energy beam below optical spectrum.

Highlights

Surface plamon polaritons (SPP) is an optical excitation coupling mode which propagates along two different medium interfaces e.g. on the metal-dielectric [1]
The other anti-symmetric lossy spoof surface plasmons (SSP) mode is termed as short-range SSP (SRSSP)
Considering the lower propagation losses of symmetric SSP mode on the symmetric structure [16], it is termed as long-range SSP (LRSSP) below

Summary

Introduction

Surface plamon polaritons (SPP) is an optical excitation coupling mode which propagates along two different medium interfaces e.g. on the metal-dielectric [1]. As the metal film thickness decreases, the field of SPP mode on the single upper and lower interface can couple with each other, a new symmetric SPP mode occurs on the structure This low loss symmetric SPP mode on the double-layer metal-dielectric interfaces is termed as long-range SPP (LRSPP) [2]. Damping losses of SSP mode can deteriorate the performance of every plamonic device and system both for passive and active ones especially in high frequency band [9,10, 14,15] This issue can be addressed by using low-loss SSP mode on the doubly-corrugated metal surfaces [14,15,16]. It is shown that the propagation loss of SRSSP mode can be reduced largely within asymmetric regime which can open up new avenues to develop some SRSSP-based high-performance devices such as low-loss filters, sensors and enhanced radiation source in THz band

Dispersion theory

Results and Discussions

Conclusions