Speaker: Fabian Wietschorke, TU Munich

Zoom: https://ucdavis.zoom.us/j/93899298889

Title: Defect engineering in Superconducting Nanowire Single-Photon Detectors

Abstract: 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 also at long wavelengths, low dark count rate and low timing jitter make them ideal for applications that require the detection of single photons like quantum key distribution, photonic quantum computing, or deep space optical communication. SNSPDs are especially suited for photonic integrated circuits and can be fabricated on waveguides of various shapes. In this contribution, we present our recent results on enhancing the efficiency of NbTiN SNSPDs via helium ion irradiation as a tool for defect engineering. For 10 nm thick NbTiN SNSPDs we observe an increase of system detection efficiency from <2% to 43% and saturating internal detection efficiency at 4 K for 780 nm photons after irradiation with He ions. 

Moreover, we present a special He ion irradiation technique , which can be used to counteract the current crowding effect, an inherent issue of meander-type SNSPDs that reduces the maximum applicable bias current due to the increased current density in the 180° turns. This allows to enhance the detection efficiency while keeping the high switching current of an unirradiated device. Finally, challenges and opportunities of waveguide integrated SNSPDs on SiC waveguides as well as the compatibility with He ion irradiations are discussed.