Multiple space missions currently under study require high-performing detectors at mid-infrared wavelengths from 2 to 20 µm. However, the future availability of the IBC detectors used for JWST is in doubt, and HgCdTe detectors have difficulties at longer wavelengths. Superconducting detectors are therefore being considered as a solution to fill this technology gap. Superconducting nanowire single-photon detectors (SNSPDs) are particularly advantageous, because they are true photon-counting detectors with digital-like output signals and low dark count rates. These features make them very stable for applications like exoplanet transit spectroscopy and able to operate in photon-starved environments for applications like nulling interferometry. We have recently demonstrated SNSPDs with high internal detection efficiency at wavelengths as long as 29 µm. This talk will provide an overview of the current state of mid-IR SNSPDs and lay out the future steps needed to adapt them for exoplanet science missions.
Superconducting nanowire single-photon detectors (SNSPDs) have become the highest-performing type of single-photon detector, with demonstrations of near-unity detection efficiency, GHz count rate, and a broad wavelength range from UV to mid-IR. Scaling these detectors to large areas and pixel counts with minimal tradeoffs in their detection properties would expand the use case of SNSPDs to applications like astronomical spectroscopy, quantum imaging, or dark matter searches. In this talk, I will discuss a thermal coupling scheme enabling these large detector arrays and several array architectures to target the requirements of specific applications.
In recent years, superconducting nanowire single-photon detectors (SNSPDs) have emerged as the state-of-the-art for photodetection in infrared regime. However, there are technical challenges still need addressing, such as high non-uniformity in SNSPD arrays, high polarization sensitivity, lack of cryogenic ROIC, and lack of high-performance devices in the mid-IR regime. During this talk, I will discuss our current work on overcoming some of these challenges.
Superconducting nanowire single-photon detectors (SNSPDs) have become the gold standard for single photon detection at telecom wavelengths, and their high efficiency, high dynamic range, low timing jitter, and low dark count rates make them ideal for quantum applications. Many use cases benefit from arrays of SNSPDs, whether it’s to enable number resolution, to access higher maximum count rates, to cover larger active areas, or to provide imaging or spectroscopy capabilities. SNSPD array design typically involves a tradeoff between number of channels, active area, and timing properties. In this talk, I will discuss several applications of SNSPD arrays and describe how the applications’ different requirements affect the array and system-level design choices.
Superconducting nanowire single-photon detectors (SNSPDs) have long been the detector of choice for photon-counting applications in the near-infrared that demand high efficiency, high timing resolution and low dark counts. Extending the operation of these detectors to mid-infrared wavelengths above 2 µm would enable a host of applications in the fields of chemical and remote sensing, LIDAR and quantum optics. Pushing the range of these detectors deeper into the mid-infrared would also be of interest to the astronomical and dark matter communities. In this work we demonstrate long-wavelength sensitivity in SNSPDs by careful material and device optimization. We also show work towards efficient, low jitter devices in the mid-infrared.
We demonstrate two-photon interference and polarization entanglement at 2090 nm, constituting a crucial leap towards
free-space mid-infrared quantum communication systems in a spectral region with high atmospheric transparency and
reduced solar background.
Superconducting Nanowire Single photon Detectors (SNSPDs) offer unparalleled performance for IR photon counting, combining close to unity quantum efficiency, low intrinsic noise and ultrafast timing jitter. The ability of SNSPDs to count photons in mid-IR band up to 7 um wavelength opens up new possibilities in quantum optics, laser ranging, free space Quantum Key Distribution (QKD) and astronomy.
Here we report on development of mid-IR SNSPDs including device design, fabrication, optimisation of superconducting materials and characterisation. We present a characterisation setup covering 1.5 - 4.2 um spectral region based on tuneable optical parametric oscillator with picosecond long pulses. We then demonstrate the viability of mid infrared SNSPDs for a variety of applications and report the results from single photon light detection and ranging (LIDAR) experiment with 2.3 um photons. This work paves the way for future app in free space QKD, deep space communication and astronomy.
Single-photon counting has become an essential tool in quantum optics experiments, as well as remote sensing and life science applications. However conventional technologies such as single-photon avalanche diodes, as well as the availability of standard telecom optical components, has limited much of this work to the near infrared/telecom wavelength range. Superconducting nanowire single photon detectors (SNSPDs) have emerged in recent years as the gold standard in photon counting applications due to their low dark count rates, fast timing resolution and high efficiency [1]. SNSPDs have also demonstrated photon counting efficiency out to much greater wavelengths which enables us to explore new experimental possibilities in the mid-infrared [2].
In this work we design and fabricate mid-infrared SNSPDs and deploy them in a variety of photon counting experiments [3,4]. The devices are based on a NbTiN superconducting film integrated into an optical cavity to enhance absorption in the mid-infrared. We characterise these devices using an optical parametric oscillator, tuneable between 1.5 m and 4.2 m. We then deploy these in a proof-of-principle tabletop light detection and ranging (LIDAR) experiment at 2.3 m. LIDAR in the mid-infrared is attractive due to spectral regions of low atmospheric absorption and reduced solar background photon flux, when compared to telecom wavelengths. We also present results from a photon-pair source operating at 2 m. This is a key resource for extending quantum optics and quantum secure communications to the mid infrared domain. Pairs are generated using a custom lithium niobate crystal and detected using SNSPDs. We demonstrate two-photon interference and polarisation entanglement of the photon pairs at 2 m. This work opens the pathway to future development of quantum optics and quantum technologies in the mid-infrared spectral region.
References
[1] Gol’tsman et al Applied Physics Letters 79 705 (2001)
[2] Marisli et al Nano Letters 12 (9) 4799 (2012)
[3] G. G. Taylor et al Optics Express 26 (27) 38147 (2018)
[4] S. Prabhakar et al Science Advances 6 (13) eaay5195 (2019)
Quantum-enhanced optical technologies operating within the 2- to 2.5-μm spectral region have the potential to revolutionize emerging applications in communications, sensing, and metrology. Currently, sources of entangled photons are available at visible, near-infrared and telecom wavelengths but are strongly underdeveloped at longer wavelengths. Here, using custom-designed lithium niobate crystals for spontaneous parametric down-conversion and tailored superconducting nanowire single-photon detectors, we demonstrate two-photon interference and polarization-entangled photon pairs at 2090 nm. These results open the 2- to 2.5-μm mid-infrared window for the development of optical quantum technologies such as quantum key distribution in next-generation mid-infrared fiber communication systems and future Earth-to-satellite communications.
In this work we design, fabricate and characterize superconducting nanowire single photon detectors (SNSPDs) optimized for mid infrared operation. The mid infrared is of interest for free space applications due to lower solar background than at shorter wavelengths as well as low atmospheric absorption. We show a proof-of-principle LIDAR imaging experiment at 2.3µm showing the viability of using SNSPDs for a variety of applications in the mid infrared.
Superconducting nanowire single photon detectors (SNSPD) offer excellent performance for infrared single photon detection, combining high efficiency, low timing jitter, low dark count rates and high photon counting rates. Promising application areas for SNSPDs include quantum key distribution, space-to-ground communications and single photon remote sensing [1]. SNSPDs are typically made with ultrathin niobium nitride (NbN) films with thickness 4 nm and a superconducting transition temperature above 9 K. NbN offers high performance in the near infrared but their sensitivity drops at wavelengths beyond 2 um. There is growing interest in potential photon counting applications in the mid infrared domain (for example remote sensing of greenhouse gases in the atmosphere [2]). One way to overcome the wavelength limit in NbN SNSPDs is to use films with a lower superconducting energy gap [3]. Here we report on the study of SNSPDs fabricated with thin films of titanium nitride (TiN). We compare TiN films deposited by atomic layer deposition (ALD) and by magnetron sputtering. The TiN films range in thickness from 5 to 60 nm, with superconducting transition temperatures from ~1 K to 3.5 K. We have analyzed the films via transmission electron microscopy and variable angle spectroscopic ellipsometry. We characterize TiN SNSPDs performance from near to mid-infrared at wavelengths (1-4 um) with fast optical parametric oscillator (OPO) source. We compare the performance of TiN SNSPDs to devices based on other lower gap materials: MoSi, NbTiN, WSi.
[1] Natarajan et al Superconductor Science and Technology 25 063001 (2012)
[2] Abshire et al Laser Applications to Chemical, Security and Environmental Analysis, (Optical Society of America,
2008) paper LMA4
[3] Verma et al Applied Physics Letters 105 022602 (2014)
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