Infrared single-photon detection using NbTiN superconducting photodetectors via gap-plasmon resonances

Superconducting single-photon detectors (SSPDs) are highly sensitive devices capable of detecting individual photons with high detection efficiency, ultra-low dark count rates, and picosecond timing resolution. These detectors have various applications in quantum communication, quantum key distribution, and LIDAR. However, the reported system detection efficiency (SDE) at a wavelength of 1550 nm is less than 12% in the absence of additional resonance structures, making them unsuitable for practical applications. Here, we demonstrate a highly sensitive NbTiN superconducting photodetector integrated with a plasmonic gold nanorod array for infrared single-photon detection. By employing a plasmonic nanostructure consisting of Au nanorod/Al₂O₃/NbTiN structure, the light-matter interactions can be enhanced in the infrared regime. The critical temperature of NbTiN is around 14 K, as measured by SQUID. The FDTD calculation results show that NbTiN has lower loss and leads to a 3% improvement of the field strength compared to NbN.