1,333 research outputs found
Superconducting nanowire single photon detectors for quantum information and communications
Superconducting nanowire single photon detectors (SNSPD or SSPD) are highly
promising devices in the growing field of quantum information and
communications technology. We have developed a practical SSPD system with our
superconducting thin films and devices fabrication, optical coupling packaging,
and cryogenic technology. The SSPD system consists of six-channel SSPD devices
and a compact Gifford-McMahon (GM) cryocooler, and can operate continuously on
100 V ac power without the need for any cryogens. The SSPD devices were
fabricated from high-quality niobium nitride (NbN) ultra-thin films that were
epitaxially grown on single-crystal MgO substrates. The packaged SSPD devices
were temperature stabilized to 2.96 K +/- 10 mK. The system detection
efficiency for an SSPD device with an area of 20x20 was found to be
2.6% and 4.5% at wavelengths of 1550 and 1310 nm, respectively, at a dark count
rate of 100 c/s, and a jitter of 100 ps full width at half maximum (FWHM). We
also performed ultra-fast BB84 quantum key distribution (QKD) field testing and
entanglement-based QKD experiments using these SSPD devices.Comment: 7 pages, 10 figure
Superconducting nanowire single-photon detectors with non-periodic dielectric multilayers
We present superconducting nanowire single-photon detectors (SSPDs) on non-periodic dielectric multilayers, which enable us to design a variety of wavelength dependences of optical absorptance by optimizing the dielectric multilayer. By adopting a robust simulation to optimize the dielectric multilayer, we designed three types of SSPDs with target wavelengths of 500 nm, 800 nm, and telecom range respectively. We fabricated SSPDs based on the optimized designs for 500 and 800 nm, and evaluated the system detection efficiency at various wavelengths. The results obtained confirm that the designed SSPDs with non-periodic dielectric multilayers worked well. This versatile device structure can be effective for multidisciplinary applications in fields such as the life sciences and remote sensing that require high efficiency over a precise spectral range and strong signal rejection at other wavelengths
Free space-coupled superconducting nanowire single photon detectors for infrared optical communications
This paper describes the construction of a cryostat and an optical system
with a free-space coupling efficiency of 56.5% +/- 3.4% to a superconducting
nanowire single-photon detector (SNSPD) for infrared quantum communication and
spectrum analysis. A 1K pot decreases the base temperature to T = 1.7 K from
the 2.9 K reached by the cold head cooled by a pulse-tube cryocooler. The
minimum spot size coupled to the detector chip was 6.6 +/- 0.11 {\mu}m starting
from a fiber source at wavelength, {\lambda} = 1.55 {\mu}m. We demonstrated
efficient photon counting on a detector with an 8 x 7.3 {\mu}m^2 area. We
measured a dark count rate of 95 +/- 3.35 kcps and a system detection
efficiency of 1.64% +/- 0.13%. We explain the key steps that are required to
further improve the coupling efficiency.Comment: 16 pages, double-space
Single-Photon Counting Detector Scalability for High Photon Efficiency Optical Communications Links
For high photon-efficiency deep space or low power optical communications links, such as the Orion Artemis-2 Optical Communications System (O2O) project, the received optical signal is attenuated to the extent that single- photon detectors are required. For direct-detection receivers operating at 1.55 m wavelength, single-photon detectors including Geiger-mode InGaAs avalanche photon diodes (APDs), and in particular superconducting nanowire single-photon detectors (SNSPDs) offer the highest sensitivity and fastest detection speeds. However, these photon detectors exhibit a recovery time between registered input pulses, effectively reducing the detection efficiency over the recovery interval, resulting in missed photon detections, reduced count rate, and ultimately limiting the achievable data rate. A method to overcome this limitation is to divide the received optical signal into multiple detectors in parallel. Here we analyze this approach for a receiver designed to receive a high photon efficiency serially concatenated pulse position modulation (SCPPM) input waveform. From measured count rate and efficiency data using commercial SNSPDs, we apply a model from which we determine the effective detection efficiency, or blocking loss, for different input signal rates. We analyze the scalability of adding detectors in parallel for different modulation orders and background levels to achieve desired data rates. Finally we show tradeoffs between the number of detectors and the required received optical power, useful for real link design considerations
Optical Properties of Superconducting Nanowire Single-Photon Detectors
We measured the optical absorptance of superconducting nanowire single photon
detectors. We found that 200-nm-pitch, 50%-fill-factor devices had an average
absorptance of 21% for normally-incident front-illumination of
1.55-um-wavelength light polarized parallel to the nanowires, and only 10% for
perpendicularly-polarized light. We also measured devices with lower
fill-factors and narrower wires that were five times more sensitive to
parallel-polarized photons than perpendicular-polarized photons. We developed a
numerical model that predicts the absorptance of our structures. We also used
our measurements, coupled with measurements of device detection efficiencies,
to determine the probability of photon detection after an absorption event. We
found that, remarkably, absorbed parallel-polarized photons were more likely to
result in detection events than perpendicular-polarized photons, and we present
a hypothesis that qualitatively explains this result. Finally, we also
determined the enhancement of device detection efficiency and absorptance due
to the inclusion of an integrated optical cavity over a range of wavelengths
(700-1700 nm) on a number of devices, and found good agreement with our
numerical model.Comment: will appear in optics express with minor revision
Multi-channel SNSPD system with high detection efficiency at telecommunication wavelength
We developed a four-channel superconducting nanowire single-photon detector
system based on a Gifford-McMahon cryocooler. All channels showed a system
detection efficiency (at a 100 Hz dark-count rate) higher than 16% at 1550 nm
wavelength, and the best channel showed a system DE of 21% and 30% at 1550 nm
and 1310 nm wavelength, respectively.Comment: 10 pages, 4 figure
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