Nanoscale aluminum plasmonic waveguide with monolithically integrated germanium detector

Surface plasmon polaritons have rapidly established themselves as a promising concept for molecular sensing, near-field nanoimaging, and transmission lines for emerging integrated ultracompact photonic circuits. In this letter, we demonstrate a highly compact surface plasmon polariton detector based on an axial metal-semiconductor-metal nanowire heterostructure device. Here, an in-coupled surface plasmon polariton propagates along an aluminum nanowire waveguide joined to a high index germanium segment, which effectively acts as a photoconductor at low bias. Based on this system, we experimentally verify surface plasmon propagation along monocrystalline Al nanowires as thin as 40 nm in diameters. Furthermore, the monolithic integration of plasmon generation, guiding, and detection enables us to examine the bending losses of kinked waveguides. These systematic investigations of ultrathin monocrystalline Al nanowires represent a general platform for the evaluation of nanoscale metal based waveguides for transmission lines of next generation high-speed ultracompact on-chip photonic circuits.