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Article

Superconducting Nanowire Single Photon Detector for Coherent Detection of Weak Signals

IEEE Transactions on Applied Superconductivity. 2016. Vol. 27. No. 4. P. 2200705.
Lobanov Y., Shcherbatenko M., Semenov A., Kovalyuk V., Kahl O., Ferrari S., Korneev A., Ozhegov R., Kaurova N., Voronov B. M., Pernice W. H., Goltsman G.

Traditional photon detectors are operated in direct detection mode, counting incident photons with a known quantum efficiency. Here we have investigated a Superconducting-Nanowire-Single-Photon-Detector (SNSPD) operated as a photon counting mixer at telecommunication wavelength around 1.5 micrometers. This regime of operation combines the excellent sensitivity of a photon counting detector with the excellent spectral resolution given by the heterodyne technique. Advantageously, we have found that low LO power of the order of hundreds of femtowatts to a few picowatts is sufficient for clear observation of the incident test signal with the sensitivity approaching the quantum limit. With further optimization, the required LO power could be significantly reduced, which is promising for many practical applications, such as development of receiver matrices or recording ultra-low signals at a level of less-than-one-photon per second.

In addition to a traditional NbN-based SNSPD operated with normal incidence coupling, we also use detectors with a travelling wave geometry, where a NbN nanowire is placed on the top of a Si3N4 nanophotonic waveguide. This approach is fully scalable and a large number of devices could be integrated on a single chip.