Large area single photon detectors based on parallel configuration NbN nanowires

The authors present superconducting single photon detectors (SSPDs) based on parallel nanostrips with an area up to 40 × 40 μm2. The SSPDs presented here are based on 100 nm wide ultrathin NbN nanostrips with a filling factor of 40%. The devices are fabricated by extending the standard electron beam lithography (EBL) patterning process to those densely structured large areas. By a thorough characterization it is shown that the electrical properties of the parallel SSPDs are comparable with those of smaller devices, as expected, proving in this way that the extended EBL process results in uniform nanostrips also in large area detectors. Furthermore, the estimated maximum count rate of the 40 × 40 μm2 parallel SSPDs was 33 MHz, showing that the parallel nanostrip configuration is much faster when compared with standard meandered serial SSPDs. The successful extension of parallel SSPDs to a large area coverage opens a new route to the use of such detectors also with multimode fibers