Wedge hybrid plasmonic THz waveguide with long propagation length and ultra-small deep-subwavelength mode area.

Chengcheng Gui,Jian Wang

doi:10.1038/srep11457

Abstract

We present a novel design of wedge hybrid plasmonic terahertz (THz) waveguide consisting of a silicon (Si) nanowire cylinder above a triangular gold wedge with surrounded high-density polyethylene as cladding. It features long propagation length and ultra-small deep-subwavelength mode confinement. The mode properties of wedge hybrid plasmonic THz waveguide are comprehensively characterized in terms of propagation length (L), normalized mode area (Aeff /A0), figure of merit (FoM), and chromatic dispersion (D). The designed wedge hybrid plasmonic THz waveguide enables an ultra-small deep-subwavelength mode area which is more than one-order of magnitude smaller compared to previous rectangular one. When choosing the diameter of Si nanowire cylinder, a smaller diameter (e.g. 10 μm) is preferred to achieve longer L and higher FoM, while a larger diameter (e.g. 60 μm) is favorable to obtain smaller Aeff /A0 and higher FoM. We further study the impacts of possible practical fabrication errors on the mode properties. The simulated results of propagation length and normalized mode area show that the proposed wedge hybrid plasmonic THz waveguide is tolerant to practical fabrication errors in geometry parameters such as misalignment in the horizontal direction, variation of wedge tip angle, and variation of wedge tip curvature radius.

Highlights

The existing surface plasmons frequency is achievable by cutting holes or grooves in metal surfaces to increase the penetration of surface electromagnetic fields into the metal[8,9,10]
In the designed wedge hybrid plasmonic THz waveguide, a float-zone high-resistivity silicon (Si) nanowire cylinder, which has a diameter of d and a permittivity of εd = 1 1.6827 at 1 THz25, is placed above a triangular gold wedge as the metal substrate
Compared to the mode distribution of rectangular hybrid plasmonic THz waveguide as shown in Fig. 1(e), it can be seen from Fig. 1(f) that wedge hybrid plasmonic THz waveguide features greatly reduced deep-subwavelength mode confinement

Summary

Introduction

The existing surface plasmons frequency is achievable by cutting holes or grooves in metal surfaces to increase the penetration of surface electromagnetic fields into the metal[8,9,10]. The proposed wedge hybrid plasmonic THz waveguide features long propagation length and ultra-small deep-subwavelength mode confinement.

Results

Conclusion