Study of the interaction of surface waves with a metallic nano-slit via the finite-difference time-domain method

Authors: Ung, Bora
Advisor: Sheng, Yunlong
Abstract: The study of the interference of the surface plasmon polariton (SPP) with the incident plane wave on a subwavelength metallic slit has become recently a fundamental subject of research in the domain of plasmonics. One of the objectives is to better understand the phenomenon of enhanced optical transmission through the nano-slit. Using the numerical method of finite-difference time-domain (FDTD), we have investigated the coupling mechanisms of the SPP inside the nano-slit. The objective of this project first consists in the conception and implementation of a flexible and robust FDTD algorithm capable of simulating the interaction between electromagnetic sources and metallic nanostructures. The algorithm that we have developed on the Matlab platform is able to model two-dimensional dispersive dielectric structures. The second and main objective is to use this FDTD simulator to investigate the coupling mechanisms between the SPP and a nano-slit pierced into a thin silver film. Our analysis demonstrates that the incident SPP is scattered by the inner edge of the slit and that the scattered waves induce oscillating electric charges on the slit edges which reradiate electromagnetic energy inside the slit. Moreover, these electric charges generate new SPPs on the slit walls which contribute to the formation of Fabry-Pérot modes along the central slit axis. We also show the formation of Fabry-Pérot modes set up by the multi-reflections of scattered waves between the slit walls. The combination of these two Fabry-Pérot modes produces an asymmetric field distribution inside the slit. We demonstrate that the phase of the SPP relatively to the normal incident beam determine the conditions of constructive and destructive interference which correspond, respectively, to the enhancement and suppression of the optical transmission through the nano-slit. Finally, we have confirmed the theory of interference between the induced fields by the SPP and incident normal beam via the superposition of their instantaneous fields.
Document Type: Mémoire de maîtrise
Issue Date: 2007
Open Access Date: 13 April 2018
Grantor: Université Laval
Collection:Thèses et mémoires

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