Ultrabroadband optical circular polarizers consisting of double-helical nanowire structures.

Recently, it was demonstrated by Gansel et al. [Science 325, 1513 (2009)] that 3D single-helical metamaterials can serve as broadband circular polarizers in the IR range. In this study, we propose a structured metamaterial with double-helical nanowires to construct circular polarizers with boarder wavelength bands in the visible-light and near-IR regions. Using the finite-difference time-domain method, we confirmed that the circular polarizers with the double-helical structures have operation bands more than 50% broader than those of the single-helical structures.