Superconducting nanowire single-photon detectors (SNSPDs) are a key building block in photon-based quantum computation and communication. To realize a scalable photonic device, integration of SNSPDs on waveguides is necessary. Hereby, one of the most promising waveguide materials is lithium niobate-on-insulator (LNOI). To find the ideal superconductor growth conditions, in this case NbTiN on LNOI, we created a series of superconducting films, while varying the superconductors stoichiometry. Here, the produced SNSPDs become more sensitive at a higher nitrogen content, while for lower amounts of nitrogen the recovery time is reduced, allowing for a direct correlation of sputter conditions and SNSPD performance.
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.
Rapid development in integrated optoelectronic devices and quantum photonic architectures creates a need for optical fiber to chip coupling with low losses. Here we present a fast and generic approach that allows temperature stable self-aligning connections of nanophotonic devices to optical fibers. We show that the attainable precision of our approach is equal to that of DRIE-process based couplings. Specifically, the initial alignment precision is 1.2±0.4 μm, the average shift caused by mating < 0.5 μm, which is in the order of the precision of the concentricity of the employed fiber, and the thermal cycling stability is < 0.2 μm. From these values the expected overall alignment offset is calculated as 1.4 ± 0.4 μm. These results show that our process offers an easy to implement, versatile, robust and DRIE-free method for coupling photonic devices to optical fibers. It can be fully automated and is therefore scalable for coupling to novel devices for quantum photonic systems.
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