Enhancement of superconducting nanowire single-photon detectors via local helium ion irradiation

Superconducting nanowire single-photon detectors (SNSPDs) play a significant role in photonic quantum technologies and for general faint light detection. Their excellent performance metrics, consisting of high detection efficiency and low timing jitter make them ideal for applications like quantum key distribution or deep space optical communication. We present our recent results on enhancing the efficiency of NbTiN SNSPDs via helium ion irradiation, increasing the system detection efficiency of a 10 nm thick SNSPD from <2% to a saturating efficiency of 43%. Moreover, we show how He ion irradiation can be used to counteract the current crowding effect by irradiating only the straight segments of the detector. With this special irradiation technique, we achieved unitary quantum efficiency for single-photons with wavelengths of 780 nm and 1550 nm and dark count rates down to 7 mHz.