Optimization of Plasmonic Nano-Antennas
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1077-L02-01
Optimization of Plasmonic Nano-Antennas Kursat Sendur, Orkun Karabasoglu, Eray Abdurrahman Baran, and Gullu Kiziltas Sabanci University, Istanbul, 34956, Turkey ABSTRACT The interaction of light with plasmonic nano-antennas is investigated. First, an extensive parametric study is performed on the material and geometrical effects on dipole and bow-tie nano-antennas. The transmission efficiency is studied for various parameters including length, thickness, width, and composition of the antenna as well as the wavelength of incident light. The modeling and simulation of these structures is done using 3-D finite element method based fullwave solutions of Maxwell’s equations. Next, a modeling-based automated design optimization framework is developed to optimize nano-antennas. The electromagnetic model is integrated with optimization solvers such as gradient-based optimization tools and genetic algorithms. INTRODUCTION Nano-optical applications, such as scanning near-field optical microscopy [1] and data storage [2], require intense optical spots beyond the diffraction limit. Nano-antennas [3-4] can obtain very small optical spots, but their ability to obtain optical spots beyond the diffraction limit is not sufficient for practical applications. In addition to a very small optical spot, a nanoantenna should provide high transmission efficiency for practical applications. The transmission efficiency of a nano-antenna determines the data transfer rate of storage devices and scan times of near-field optical microscopes. Therefore, the efficiency of nano-antennas should be optimized for potential utilization in practical applications. Optimization of nano-antennas is crucial for understanding their potential and limitations for emerging plasmonic applications. The interaction of antennas with electromagnetic waves has been thoroughly investigated at microwave frequencies. Scaling and optimization rules do not apply at optical frequencies [4]. At visible and infrared frequencies the underlying physics of the interaction of light with metallic nano-antennas is complicated due to the behavior of metals as strongly coupled plasmas [5-8]. Experimental studies have shown light localization using both dipole [9] and bow-tie [10] nanoantennas. A brute-force optimization study of these structures is not practical due to large number of parameters. There is a need for a systematic optimization of these structures. In this study, we develop a modeling-based automated design optimization framework to optimize nano-antennas. The modeling and simulation are done using 3-D finite element method (FEM), which is integrated with optimization solvers such as genetic algorithms and gradient based optimization tools. First, an extensive parametric study is performed on the material and geometrical effects. Then the proposed design framework is used to optimize nano-antennas. DIPOLE AND BOW-TIE PLASMONIC NANO-ANTENNAS To couple incident electromagnetic energy with small scale electronic devices, antennas have been utilized. The anten
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