Nowadays, Superconducting Nanowire Single-Photon Detectors (SNSPDs) play a significant role in quantum technologies and for general faint light detection. Typically, NbTiN SNSPDs are at most 8nm thick to achieve single-photon sensitivity. However, as absorption increases with film thickness, it is desirable to use thicker films of 10 or 12nm considering that the absorption probability places an upper limit for the achievable system detection efficiency. In this contribution, we present for the first time 12nm thick NbTiN SNSPDs that show an increase of system detection efficiency from less than 0.01% to 55% and saturating internal detection efficiency at 4K after irradiation with helium ions. Furthermore, we investigated the influence of helium ion irradiation on the transport properties of the underlying superconducting films.
In recent years, Superconducting Nanowire Single-Photon Detectors (SNSPDs) have obtained tremendous attention as a possible key technology for photonic quantum processing and faint light detection.
Here, we present our recent progress on engineering of the properties of NbTiN SNSPDs fabricated on various substrates measured. We discuss approaches to simultaneously improve the most important figures of merit (DCR, dead time, timing jitter, efficiency) as well as efficient characterization methods. Specifically, for the latter we investigate the impact of the substrate material on the performance parameters as well as the fundamental interrelation of the resulting voltage pulse properties, such as pulse height, rise time and timing jitter, and their dependence on the applied bias current.
KEYWORDS: Superconductors, Single photon detectors, Sensors, Nanowires, Quantum efficiency, Near infrared, Deep reactive ion etching, Thin films, Single photon, Resonators
In this work, recent developments in the study of Superconducting Nanowire Single Photon Detectors (SNSPDs) are presented. This devices properties highly depends on the quality of the superconducting films from which they are fabricated. Here, we study some film properties for SNSPDs made out of NbTiN and MoSi in function of the deposition parameters. Subsequently we focus on the properties of the fabricated detector, such as efficiency, timing resolution and energy sensitivity.
We fabricate an integrated photonic circuit with emitter, waveguide and detector on one chip, based on a hybrid superconductor-semiconductor system. We detect photoluminescence from self-assembled InGaAs quantum dots on-chip using NbN superconducting nanowire single photon detectors. Using the fast temporal response of these detectors we perform time-resolved studies of non-resonantly excited quantum dots. By introducing a temporal filtering to the signal, we are able to resonantly excite the quantum dot and detect its resonance fluorescence on-chip with the integrated superconducting single photon detector.
Rudolf Gross, J. Klein, B. Wiedenhorst, C. Hoefener, U. Schoop, J. Philipp, M. Schonecke, F. Herbstritt, L. Alff, Yafeng Lu, A. Marx, S. Schymon, S. Thienhaus, W. Mader
We have grown heteroepitaxial thin film structures composed of various transition metal oxides such as the colossal magnetoresistance manganites, superconducting cuprates, ruthenates as well as insulating titanates on SrTiO3, NdGaO3 and LaAlO3 substrates using a UHV laser molecular beam epitaxy (laser-MBE) system. The film growth was controlled in-situ using high pressure RHEED as well as scanning probe techniques (AFM/STM). The fabricated films were analyzed by x-ray diffraction, transmission electron microscopy and the measurement of the transport properties. The manganite, ruthenate and titanate thin film structures show good epitaxy with small mosaic spread. The observation of RHEED oscillations during the film deposition indicates a layer by layer growth mode. This is further supported by the observed small surface roughness of typically less than 3 nm rms for a 100 nm thick film. We also could find a clear correlation between the observed RHEED pattern and the surface morphology measured by AFM/STM. Our analysis shows that UHV laser MBE is well suited for the fabrication of complicated heteroepitaxial thin film structures required for oxide electronics.
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