Utilizing niobium plasmonic perfect absorbers for tunable near- and mid-IR photodetection

With the fast development of single photon-based technologies such as quantum computing and quantum cryptography, conventional avalanche photodiodes as single photon detectors are not the optimum tools anymore. They are currently replaced by Superconducting Nanowire Single Photon Detectors (SNSPDs) based on the superconducting to normal conducting phase transition. The current challenge with SNSPDs lies in overcoming the trade-off between detection efficiency and recovery time. While a large active area will lead to high detection efficiency, the associated high kinetic inductance causes a long recovery time. Plasmonic effects can play an important role in the absorption enhancement of SNSPDs. Nanostructuring with a suitable geometry can provide a high-absorption cross-section at the intrinsic nanowire surface plasmon resonance, which can be significantly larger than their geometric cross-section. We present a photodetector based on the intrinsic localized surface plasmon resonance of a niobium nanowire, which is one of the common superconductors with low kinetic inductance. Additionally, we are increasing the absorption of our nanostructures even further using a plasmonic perfect absorber scheme. We fabricated a plasmonic perfect absorber superconducting photodetector, investigated its response to external light at resonance, and proved its plasmonic behavior as evidenced by its polarization dependence.