Plasmonics and Antenna Effect Mediated Super Absorption in Ultrathin Film via Core/Shell Design

The conventionally low-absorbing ultrathin film is recently shown to obtain a high absorption via a strong optical interference effect by coating the highly absorbing film onto a metal layer. In this letter, through finite-element simulation and modal analysis, we report that the optical performance of an ultrathin semiconductor film can be significantly improved by further nanostructuring the ultrathin semiconductor film. Through wrapping the film onto a metallic nanowire in either lying or vertical configuration, a high dielectric resonance antenna effect and a strong plasmonic resonance can be excited simultaneously, which enables an extremely high and broadband optical absorption. Especially, with introducing the vertical metal-core/semiconductor-shell design, the peak absorption can be up to >300% under an extremely high field-confinement effect, leading to an integrated photocurrent density, which can be 25 times higher than that of the planar system. The proposed scheme is useful for the realization of compact, low-cost, and highly absorbing systems for photon absorbing, solar-energy harvesting, and photodetection applications.