SNSPD | laboratorioattanasio

Superconducting films for Superconducting Nanowires Single Photon Detectors (SNSPD)

Superconducting Single-Photon Detectors are among the best established technology based on superconducting materials. Nevertheless, the community is continuously committed to improve the detector performances. The group was recently involved in this field of research.

The first SNSPDs based on NbRe films 8-nm-thick were realized in collaboration with TU Delft and its spin-off Single Quantum. NbRe films with their polycrystalline structure made of small crystallites, their disorder-dominated transport properties, and their relatively high value of the critical temperature are a promising alternative between the materials-of-choice such as NbN or NbTiN and amorphous superconductors.

The main key parameters which characterize the devices operation, such as critical current density, eﬃciency, dark counts rate, time jitter, and recovery time were estimated at T=2.8 K. The study reveals that the detectors performances in terms of time resolution, such as recovery times between about 8 and 19 ns and time jitter of about 35 ps, are competitive with many of the already employed materials. In addition, the normalized internal efficiency, which shows robust saturation at lower wavelengths, also tends to saturate at 1301 nm.

NbReN films were recently suggested as an alternative material as well. Indeed, the microscopic properties of NbReN films which may produce improvement of some of the main figures of merit of NbRe-based detectors. The new superconductor has enhanced resistivity, which should produce larger hot-spots, shorter rise time, and better optical absorption, as well as comparable qp relaxation times.