Delivered by Ingenta to: Chinese University of Hong Kong IP: 146.185.202.70 On: Fri, 17 Jun 2016 08:13:26 Copyright: American Scientific Publishers RESEARCH ARTICLE Copyright © 2015 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Computational and Theoretical Nanoscience Vol. 12, 909–915, 2015 Backside Nanoslot Excited Sub-Wavelength Grating-Coupled Cu-Strip Plasmonic Waveguides Houxiao Wang 1 2 3 ∗† , Rakesh Ganpat Mote 3 4† , Wei Zhou 2 3 ∗ , Er Ping Li 3 ∗ , and Ping Bai 3 1 School of Mechanical Engineering, Jiangsu University, Zhenjiang, 212013, Jiangsu, P. R. China 2 School of Mechanical and Aerospace Engineering, Nanyang Technological University, 639798, Singapore 3 Advanced Photonics and Plasmonics Division, A*STAR Institute of High Performance Computing, 138632, Singapore 4 Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India The backside nanoslot excited sub-wavelength grating-coupled Cu-strip silica-based plasmonic waveguides were developed using the finite difference time domain (FDTD) simulation method. The performance of the designed waveguides was simulated, and the effects of copper film thickness on plasmonic wave propagation were analyzed for relatively low propagation loss design. The designed waveguides could achieve unidirectional guiding of the excited surface plasmon polaritons (SPPs) with sub-wavelength lateral confinement and acceptable propagation length at microscale, and the recommended design for the sub-wavelength grating-coupled Cu-strip SPP waveguide was given, with the potential applications for the fiber-optic devices or elements. Keywords: Backside Nanoslot Excitation, Sub-Wavelength Grating Reflector, Surface Plasmon Polaritons, Cu-Strip Plasmonic Waveguides. 1. INTRODUCTION Metamaterials are artificial structures exhibits double neg- ative properties such as negative permittivity and nega- tive permeability. If quantum properties of metamaterial are considered, they can control electromagnetic radiations by quantum mechanics. 1 2 Surface plasmon polaritons (SPPs) can be launched via coupling between the inci- dent light and surface plasmons in plasmonic structures/ metamaterials through the interaction of light with metal- dielectric structures. 3–7 The SPP photonic circuits consist of various components (e.g., the subwavelength plasmonic waveguides acting as optical interconnects) where the inci- dent light is firstly converted into SPPs (charge density oscillations at metal-dielectric interfaces, i.e., longitudi- nal waves with magnetic vector perpendicular to the plane of incidence or p-polarized transverse-magnetic waves), and then propagating and interacting with different devices before being recovered as the freely propagating light. 8 9 Waveguides supporting highly-confined optical modes are important to achieve compact integrated photonic devices, and plasmonic waveguides may guide the sub-wavelength optical modes and optically transmit information from one electronic component to another in the integrated ∗ Authors to whom correspondence should be addressed. † These two authors contributed equally to this work. nanoelectronic circuits (the one-dimensional metallic nano- structures, e.g., nanowires, strips, or nanoparticle chains, have been widely used as the optical waveguides). 10–15 As a new device technique emerged recently, the plasmonic waveguide makes it possible to integrate plasmonic, elec- tronic, and conventional dielectric photonic devices on the same chip. 16 Propagating SPPs can support higher bandwidths than electrical signals carried by conventional metal wires. 17 18 Compared with the dielectric waveguides, plasmonic devices can concentrate light to smaller volumes (this makes it possible to realize optical nanocircuitry and even- tually bring light into nanoelectronics) and enhance light- matter interactions despite the problem of metal-induced attenuation or loss, 17 19 20 among which the plasmonic waveguides can guide both light and electrical current with high confinement to realize efficient coupling to their outside microscopic or nanoscopic world. 13 21 More- over, plasmonic waveguides have the ability to confine and propagate light over short distances (typically less than one hundred microns) through coupling electromag- netic waves to SPPs and then emitted at their oppo- site ends, and this short propagation length is actually the trade-off between the propagation loss and the con- finement of plasmonic waves below the diffraction limit (typically on the order of a hundred of nanometers). J. Comput. Theor. Nanosci. 2015, Vol. 12, No. 6 1546-1955/2015/12/909/007 doi:10.1166/jctn.2015.3826 909