Topology Optimization-Based Computational Design Methodology for Surface Plasmon Polaritons

Abstract

This paper presents the topology optimization-based computational design methodology for nanostructures in surface plasmon polaritons. Using the proposed method, nanostructures can be designed solely based on the user’s desired performance specification for the surface plasmon polaritons. This topology optimization-based computational design methodology is implemented based on the material interpolation with hybrid formulation of logarithmic and power law approaches, to mimic the metal surface with exponential decay of the electromagnetic field. The constructed computational design problem is analyzed using the continuous adjoint method, and the filter and projection techniques are utilized to ensure the minimum length scale in the obtained nanostructures. The outlined design methodology is used to investigate the nanostructures for localized surface plasmonic resonances, extraordinary optical transmission, and surface plasmonic cloaking, respectively. For localized surface plasmonic resonances and extraordinary optical transmission, the metallic nanostructures are designed with spectra peaks at the prescribed wavelengths and the shift of the spectra peak is controlled by solving the computational design problem corresponding to a different incident wavelength; for surface plasmonic cloaking, the cloak covered at a curved metal-dielectric interface is designed to bound the surface plasmon polariton at the interface and remove the radiation, where the conventional simple isotropic dielectric readily available in nature is used instead of the material possessing gradient electromagnetic properties with challenges on realization for optical frequencies.