Nano-scaled superconducting meanders as single-photon detectors

Gregory N Gol'tsman, Alexander A. Korneev, V Izbenko +9 more

Robert Vedin

Mei Yang, Lihua Liu, Luhui Ning +5 more

Superconducting nanowire single photon detector (SNSPD), as a new type of superconducting single photon detector (SPD), has a broad application prospect in quantum communication and other fields. In order to prepare SNSPD with high performance, it is necessary to fabricate a large area of uniform meander nanowires, which is the core of the SNSPD. In this paper, we demonstrate a process of patterning ultra-thin NbN films into meander-type nanowires by using the nano-imprint technology. In this process, a combination of hot embossing nano-imprint lithography (HE-NIL) and ultraviolet nano-imprint lithography (UV-NIL) is used to transfer the meander nanowire structure from the NIL Si hard mold to the NbN film. We have successfully obtained a NbN nanowire device with uniform line width. The critical temperature ( T c ) of the superconducting NbN meander nanowires is about 5 K and the critical current ( I c ) is about 3.5 μA at 2.5 K.

L. Parlato, Daniela Salvoni, Halima Giovanna Ahmad +11 more

When superconducting materials work as Single Photon Detectors (SPD) they are patterned in nanostrips about 100 nm wide with a typical meander structure to increase the photosensitive area. Moreover, they are biased by a DC current close to the critical current to have higher efficiency. The critical current could be non uniform mainly in proximity of the turn bends producing an increase of the dark count events. In this work MoSi nano-strips covered with a very thin (2 nm) layer of Al, have been realized and characterized in a wide interval of temperatures from 6 K down to 7 mK to investigate the critical current as a function of the temperature and then its uniformity in the presence of sharp corners and/or turn-arounds. Finally, the counts rates were recorded by a nano-meander under irradiation at two different wavelengths λ = 650 nm and 1550 nm, respectively, and compared with the events in the dark regime.

Berggren, Anant, Baek +11 more

Jia-Min Xiong, Weijun Zhang, Guangzhao Xu +8 more

Abstract To facilitate high optical coupling efficiency and absorptance, the active area of a superconducting nano/microstrip single-photon detector (SNSPD/SMSPD) is often designed as a meander configuration with a high filling factor (e.g. ⩾0.5). However, the switching current (I sw) of SNSPD/SMSPD, at which the detector switches into the normal state, is significantly suppressed by a geometry-induced ‘current crowding effect’, where there are sharp bends in the strip. Here, we propose and experimentally verify an alternative method to reduce current crowding both in SNSPD and SMSPD by directly increasing the thickness of the bends through the deposition and lift-off of a secondary superconducting film. We measure and compare the performance of SNSPDs and SMSPDs with different filling factors and bend configurations, with or without thickened bends. Improvements for detectors were observed in detection efficiency, intrinsic dark count rate, and time jitter, owing to the enhanced I sw. Our method provides a promising way of optimizing SNSPD/SMSPD detection performance.