Wedge Angle-Dependent Propagation Characteristics of Two Coupled Semi-Infinite Au Rib Nanoplasmonic Waveguides
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Wedge Angle-Dependent Propagation Characteristics of Two Coupled Semi-Infinite Au Rib Nanoplasmonic Waveguides Yin-Song Liao 1,2 & Po-Han Lee 2 & He-Qian Shen 2 & Jia-Ren Wu 1 & Sheng Hsiung Chang 1,3 Received: 5 August 2020 / Accepted: 6 September 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The wedge angle-dependent propagation characteristics of two coupled semi-infinite Au rib nanoplasmonic waveguides are investigated using the three-dimensional finite-difference time-domain (3D FDTD) method with the fast Fourier transform and curve fitting techniques. The simulation results show that the propagation loss and modal index of the fundamental mode are closely related to the field distribution of the supermode which can be manipulated by varying the wedge angle from 75° to 100°. Understanding of the nanostructure-induced enhancement of the propagation characteristics of nanoplasmonic waveguides helps us find the best way to optimize the metallic waveguiding structures. Keywords Nanoplasmonic waveguide . Wedge angle-dependent propagation characteristics . Modal field distribution . Edge localization . Partial orthogonal decoupling of electric fields
Introduction Nanoplasmonic waveguides [1–3], which have been intensively investigated in the past two decades, can be used to realize compact integrated optical circuits [4, 5] due to the localized modal field. Surface plasmon waves (SPWs) can propagate at the dielectric/metal interfaces, which naturally confine the electromagnetic waves within a twodimensional (X-Y) plane with short penetration depths on the dielectric and metal sides. The summation of the two penetration depths determines the modal size along the perpendicular direction (Z direction). Nanoplasmonic waveguide structures can be realized by the creation of Yin-Song Liao and Po-Han Lee contributed equally to this work. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11468-020-01290-9) contains supplementary material, which is available to authorized users. * Sheng Hsiung Chang [email protected] 1
Department of Physics, Chung Yuan Christian University, Taoyuan 320314, Taiwan, Republic of China
2
The Affiliated Senior High School of National Taiwan Normal University, Taipei 106, Taiwan, Republic of China
3
R&D Center for Membrane Technology and Center for Nanotechnology, Chung Yuan Christian University, Taoyuan 320314, Taiwan, Republic of China
additional lateral confinement by texturing the surface or the addition of dielectric strip to the top of the metallic surface. The application of a dielectric-loaded metal surface is the simplest way to form a nanoplasmonic waveguide [6]. Wedge [7, 8], V-groove [9, 10], and two coupled semi-infinite rib [11, 12] nanoplasmonic waveguides provide lateral confinement for guiding SPWs along a specific direction while maintaining relatively long propagation lengths. The fundamental modes of the metallic wedge and V-groove nanoplasmonic waveguides are mainly confined near the edg
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