State-of-the-art Superconducting Nanowire Single Photon Detectors based on low-Tc materials reach 100% quantum efficiency. However, the response time is limited to >1-10 ns. Recently, it has been shown that due to a much lower kinetic inductance, a 100 ps response rate can be achieved in 120
μm-long
MgB2 nanowires. In this work, we demonstrate experimentally that such
MgB2 nanowires function as single-photon detectors for both visible (
λ= 630 nm) and infrared (
λ= 1550 nm) photons when biased close to the critical current, with a dark count rate of <10 cps.
MgB2 photodetectors over-perform NbN SNSPDs in speed by at least an order of magnitude for similar nanowire lengths. Such photodetectors offer a platform for single-photon detectors with a long thought-after combination of a large detector area and a response rate of up to 10 GHz with a single readout line.
High-efficiency superconducting nanowire single-photon detectors (SNSPDs), which have numerous applications in quantum information systems, function by using the optical cavity and the ultrasensitive photon response of their ultra-thin superconducting nanowires. However, the wideband response of superconducting nanowires is limited due to the resonance of the traditional optical cavity. Here, we report on a supercontinuum SNSPD that can efficiently detect single photons over an ultra-broad spectral range from visible to mid-infrared light. Our detection approach relies on using multiple cavities with well-separated absorbed resonances formed by fabricating multilayer superconducting nanowires on metallic mirrors with silica acting as spacer layers. Thus, we are able to extend the absorption spectral bandwidth while maintaining considerable efficiency, as opposed to a conventional single-layer SNSPD. Our calculations show that the proposed supercontinuum SNSPD exhibits an extended absorption bandwidth with increased nanowire layers. Its absorption efficiency is greater than 70% over the entire range from 400 to 2500 nm (or 400 to 3000 nm), when using two-layer (or three-layer) nanowires. As a proof of principle, the SNSPD with bilayer nanowires is fabricated based on the proposed detector architecture with simplified geometrical parameters. The detector achieves broadband detection efficiency over 60% from 950 to 1650 nm. This type of detector may replace multiple narrow band detectors in a system and find uses in the emerging and rapidly advancing field of atomic and molecular broadband spectroscopy.
Single-photon detectors have been widely used in many vital fields, such as quantum teleportation and quantum computation. Compared with other single-photon detectors, superconducting nanowire single-photon detector exhibits relatively wide response spectrum, low dark count rate and high detection efficiency. The principle of superconducting nanowire single-photon detector is demonstrated, especially on the process of the generation and the diffusion of the hotspot, and the simulation is done to illustrate this process. Many important parameters of superconducting nanowire single-photon detector are measured, such as R-T curve and photon response. Through the analysis of experimental data, the approach to improve the performance of superconducting nanowire single-photon detector is proposed.