Optically deep asymmetric one-dimensional plasmonic crystal slabs: Genetic algorithm approach

Optical asymmetry with regard to transmission has been numerically explored in one-dimensional (1D) plasmonic crystal slabs (PICSs) with the help of a genetic algorithm (GA). Optically deep asymmetric PICSs are not obtained in one-layer systems and can be achieved in unit cell structures composed of more than two layers. The optical asymmetry is classified into two types. One is ascribed to anisotropic diffraction efficiency, and the other comes from collective oscillations of particle plasmons in each metallic nanorod and can induce nearly perfect absorption over a broad band. In both asymmetry types, the degree of freedom in depth is crucial to manipulate the linear optical responses of PICSs. On the basis of the GA search, a simple design for optically asymmetric 1D PICS is extracted, which provides a standard for broadband plasmonic absorbers in both photon energy and incident angles. (C) 2009 Optical Society of America