Delivered by Ingenta to: Chinese University of Hong Kong IP: 95.85.80.42 On: Fri, 17 Jun 2016 08:16:01 Copyright: American Scientific Publishers RESEARCH ARTICLE Copyright © 2013 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Computational and Theoretical Nanoscience Vol. 10, 2276–2281, 2013 Dispersion Characteristics of Guided Plasmonic Modes in Metallic Slot Waveguides Using Method of Lines Anju Babu 1 , C. Bhagyaraj 1 , R. Ajith 1 , and Vincent Mathew 2 ∗ 1 Postgraduate and Research Department of Physics, St. Thomas College, Palai, Kerala 686574, India 2 Department of Physics, Central University of Kerala, Riverside Transit Campus, Padennakad P.O., Nileshwar, Kasaragode, Kerala 671314, India In this paper we analysed the dispersion characteristics of the mode supported by a plasmonic slot waveguide structure, using Method of Lines (MoL) and Finite Element Method (FEM). Metal slot waveguides, unlike nano-metal strip waveguides, can support bound plasmon mode for wavelengths above optical regime. The propagation properties of the mode is studied as a function of operating wavelength. Metallic slot waveguides provide the confinement of the mode to lateral size many decade times smaller than the free-space wavelength. The dependance of the mode properties on the guiding geometry and structural parameters is also analysed. It is observed that the slot width, thickness, and refractive index of the material filling the slot region strongly influence the dispersion characteristics of the mode. Keywords: Plasmonics, Slot Waveguide, Method of Lines. 1. INTRODUCTION Guiding electromagnetic waves through highly integrated photonic circuits can be achieved through bound non- radiative surface waves called Surface Plasmon Polari- tons (SPPs). 1 The SPP on the metal-dielectric interface is the key mechanism for wave propagation in miniaturized subwavelength waveguides. 2 In the past years, plasmonic waveguides have been used as an effective mechanism to provide ultrafast optical signal processing capabilities of photonics with structural dimension much more com- pact than their photonic predecessors. Thus SPP waveg- uides aim at an efficient solution to the size incompatibility problem between micrometer scale photonic devices and nanoscale electronics. 3 Different types of plasmonic waveguiding structures have been proposed over the past years like metallic nanorods, metallic nanoparticle chains, metallic photonic crystals, and thin metallic strips. 4–7 Such guiding geome- tries, operating near the surface plasmon frequency regime, incorperates trade-off between subwavelength mode confinement and the propagation loss including losses associated with metal. However, metallic slot plasmonic waveguide structures are being reported to support guided ∗ Author to whom correspondence should be addressed. modes with better confinement over a wide range of fre- quency. 8 In a slot waveguide, depending on the design characteristics, deep subwavelength localization can be obtained at the slot region due to the large refractive-index discontinuity. The small mode volume could be even useful for coupling the emission of individual quantum emitters incorporated into the slot region to guided modes, a nanoscale source of light on an optical integrated circuit. 9 Propagation of SPP through subwavelength plasmon slot waveguide structure has been investigated recently. Veronis and Fan demonstrated the existence of a bound mode in symmetric and asymmetric plasmonic slot waveguides. 8, 10 Partially filled metal slot waveguides were analyzed by Feng et al. to study enhanced field localization along with low propagation loss. 11 Three-dimensional plasmonic slot waveguides, including mirrors, bends, T -splitters and X-junctions were also been investigated. 12 However the propagation characteristics of the mode with respect to the width of slot for different dielectric materials have not been considered in detail. Since the dimension of the waveg- uide considered are well above the quantum regime, 13–15 the wave propagation can be analyzed using Maxwells theory. We employ the method of lines (MoL), a finite difference based semi-analytical scheme which is suitable to adjust the width of the slot conveniently. The results obtained were verified and field distribution has been studied using Finite 2276 J. Comput. Theor. Nanosci. 2013, Vol. 10, No. 9 1546-1955/2013/10/2276/006 doi:10.1166/jctn.2013.3198