We demonstrate efficient nanowire superconducting single photon detectors (SSPDs) based on NbN thin films grown on GaAs. NbN films ranging from 3 to 5 nm in thickness have been deposited by dc magnetron sputtering on GaAs substrates at 350 °C. These films show superconducting properties comparable to similar films grown on sapphire and MgO. In order to demonstrate the potential for monolithic integration, SSPDs were fabricated and measured on GaAs/AlAs Bragg mirrors, showing a clear cavity enhancement, with a peak quantum efficiency of 18.3% at λ=1300 nm and T=4.2 K.
We present the first nanoscale (down to approximately 50 x 50 nm(2)) detector displaying single-photon sensitivity and a nanosecond response. This type of nanodetector can also be operated in multiphoton mode, where the detection threshold can be set at N = 1, 2, 3, or 4 photons, thus allowing the mapping of photon number statistics on the nanoscale. Its operation principle based on that of hot-spot formation in superconducting nanowires allies the temporal resolution and sensitivity of superconducting single-photon detectors with subwavelength resolution and photon number discrimination. Such detectors can be of great interest for the study of nanophotonic devices at low temperature.
We report on efficient nanowire NbN superconducting single photon detectors (SSPDs), integrated with an optical cavity based GaAs/AlAs distributed Bragg reflectors, showing a detection efficiency of 18.3% at 4.2K at 1.3 μm wavelength.Superconducting nanowire single photon detectors (SSPDs) are an emerging technology that offers ultrahigh sensitivity at telecommunication wavelengths, high counting rates, broad spectral response and high temporal resolution due to low jitter values. All these features are interesting for a variety of applications such as quantum key distribution (QKD), ultra-long distance optical communication, biomedical imaging and VLSI circuit testing. SSPDs consist of an ultrathin (4 to 5 nm) NbN nanowire patterned as a meander with 100 nm typical width. The detection mechanism is based on the hot-spot process: if the nanowire is in the superconducting state and it is current-biased near its critical current I C, the absorption of a single photon can drive an entire cross-section of the nanowire to the normal state [1].Until recently, SSPDs have been fabricated only on sapphire, MgO and silicon substrates. The integration of NbN nanowires with III-V semiconductor heterostructures (e.g. GaAs-based) could open novel avenues for their application: On one hand, advanced optical structures such as microcavities and waveguides can be realized to increase the absorption and therefore the efficiency. On the other hand, it may lead to the monolithic integration of all key functionalities needed for photonic quantum information processing (photon generation, processing and detection), and therefore to integrated quantum photonic chips. Here we report the successful operation of a SSPD based on NbN nanowires grown on a GaAs substrate, and demonstrate its monolithic integration with an optical microcavity based on a GaAs/AlAs Bragg mirror. The GaAs/AlAs Bragg technology can provide very high reflectivity >99%, and allows the use of the top-illumination, as opposed to the top-mirror approach reported in ref.[2]. Figure 1: SSPD integrated with a DBR. a) Layers structure b) 2 and 3 dimensional AFM image of an NbN meander fabricated on the DBR substrate, after the etching of the NbN. A layer of ~30nm electronic resist covers the nanowires.
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