High Performance Absorber Structure Using Subwavelength Multi- branch Dimers

摘要

As the desire growing of the thin film absorption structure for various sub-wavelength applications such as photo detector, thin-film thermal emitters, thermo photovoltaic cells, and multi-color filters, we proposed a type of sub-wavelength multi-branch dimers which exhibit several tunable dipole-dipole-like plasmonic resonances and integrated it into metal-insulator-metal structure as the top layer. The structures are studied through numerical calculation by finite element method. When normal incident is considered, the novel structure shows three absorption peaks in the considered wavelength range. One peak has near-perfect absorption and the other two also show excellent absorption.. When different angle oblique incident is considered, the absorption only has slight change, which is useful to an ultrathin absorber structure. In addition, we find that the thickness of the dielectric layer can tune the absorption rates for each absorption peak. In general, the multi-branch dimers can easily tune its absorption rates and spectrum via the change of their geometric parameters such as branch lengths, branch angles, and dielectric layer thickness.