Picosecond superconducting single-photon optical detector

TLDR

The study demonstrates a supercurrent‑assisted hotspot‑formation mechanism for ultrafast detection and counting of visible and infrared photons. The detector uses an ultrathin, narrow NbN strip biased near its critical current at 4.2 K, where a photon‑induced hotspot forms a transient resistive barrier that generates a voltage pulse and heals in ~30 ps, restoring superconductivity for rapid successive photon detection. The device achieves ~20 % quantum efficiency at 0.81 µm with negligible dark counts.

Abstract

We experimentally demonstrate a supercurrent-assisted, hotspot-formation mechanism for ultrafast detection and counting of visible and infrared photons. A photon-induced hotspot leads to a temporary formation of a resistive barrier across the superconducting sensor strip and results in an easily measurable voltage pulse. Subsequent hotspot healing in ∼30 ps time frame, restores the superconductivity (zero-voltage state), and the detector is ready to register another photon. Our device consists of an ultrathin, very narrow NbN strip, maintained at 4.2 K and current-biased close to the critical current. It exhibits an experimentally measured quantum efficiency of ∼20% for 0.81 μm wavelength photons and negligible dark counts.