Towards fiber-coupled plasmonic perfect absorber superconducting nanowire photodetectors for the near- and mid-infrared

: Modern photon-based technologies are in need for fast detectors with the ability to detect photons in the near-and mid-IR efficiently. Superconducting nanowire photon detectors, which use the resistivity change upon photon incidence caused by a state transition from their superconducting to normal conducting phase, are state-of-the-art detectors. However, detectors usually suffer from low efficiency in the IR, due to their low intrinsic absorption in this spectral range. To enhance the detection efficiency, we use a plasmonic perfect absorber geometry, which utilizes a localized surface plasmon resonance and a spacer/mirror combination. We present superconducting niobium plasmonic perfect absorber nanostructures, featuring near-unity absorption, tailorable up to wavelengths of 4 µm. Further, we confirm the working principle of the plasmonic perfect absorber for wavelengths in the near-IR, which manifests itself as a polarization-dependent detector response. Finally, we demonstrate an approach of coupling the detector directly to a fiber. This might also enable ultrasensitive sensing application in the near-and mid-IR in the future.