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Kerman AJ, Yang JKW, Molnar RJ, Dauler EA, Berggren KK. Electrothermal feedback in superconducting nanowire single-photon detectors. Phys Rev B. 2009;79(10):4.
Abstract: We investigate the role of electrothermal feedback in the operation of superconducting nanowire single-photon detectors (SNSPDs). It is found that the desired mode of operation for SNSPDs is only achieved if this feedback is unstable, which happens naturally through the slow electrical response associated with their relatively large kinetic inductance. If this response is sped up in an effort to increase the device count rate, the electrothermal feedback becomes stable and results in an effect known as latching, where the device is locked in a resistive state and can no longer detect photons. We present a set of experiments which elucidate this effect and a simple model which quantitatively explains the results.
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Marsili F, Najafi F, Herder C, Berggren KK. Electrothermal simulation of superconducting nanowire avalanche photodetectors. Appl Phys Lett. 2011;98(9):3.
Abstract: We developed an electrothermal model of NbN superconducting nanowire avalanche photodetectors (SNAPs) on sapphire substrates. SNAPs are single-photon detectors consisting of the parallel connection of N superconducting nanowires. We extrapolated the physical constants of the model from experimental data and we simulated the time evolution of the device resistance, temperature and current by solving two coupled electrical and thermal differential equations describing the nanowires. The predictions of the model were in good quantitative agreement with the experimental results.
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Hu X, Zhong T, White JE, Dauler EAN Faraz, Herder CH, Wong FNC, et al. Fiber-coupled nanowire photon counter at 1550 nm with 24% system detection efficiency. Opt Lett. 2009;34(23):3607–9.
Abstract: We developed a fiber-coupled superconducting nanowire single-photon detector system in a close-cycled cryocooler and achieved 24% and 22% system detection efficiencies at wavelengths of 1550 and 1315 nm, respectively. The maximum dark count rate was ~1000 counts/s.
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Stevens MJ, Baek B, Dauler EA, Kerman AJ, Molnar RJ, Hamilton SA, et al. High-order temporal coherences of
chaotic and laser light. Opt Express. 2010;18(2):1430–7.
Abstract: We demonstrate a new approach to measuring high-order temporal coherences that uses a four-element superconducting nanowire single-photon detector. The four independent, interleaved single-photon-sensitive elements parse a single spatial mode of an optical beam over dimensions smaller than the minimum diffraction-limited spot size. Integrating this device with four-channel time-tagging electronics to generate multi-start, multi-stop histograms enables measurement of temporal coherences up to fourth order for a continuous range of all associated time delays. We observe high-order photon bunching from a chaotic, pseudo-thermal light source, measuring maximum third- and fourth-order coherence values of 5.87 ± 0.17 and 23.1 ± 1.8, respectively, in agreement with the theoretically predicted values of 3! = 6 and 4! = 24. Laser light, by contrast, is confirmed to have coherence values of approximately 1 for second, third and fourth orders at all time delays.
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Zhong T, Hu X, Wong FNC, Berggren KK, Roberts TD, Battle P. High-quality fiber-optic polarization entanglement distribution at 1.3 μm telecom wavelength. Opt Lett. 2010;35(9):1392–4.
Abstract: We demonstrate high-quality distribution of 1.3 μm polarization-entangled photons generated from a fiber-coupled periodically poled KTiOPO4 waveguide over 200 m fiber-optic cables. Time-multiplexed measurements with a 19% efficient superconducting nanowire single-photon detector at the remote location show a detected flux of 5.8 pairs / s at a pump power of 25 μW and an average two-photon quantum-interference visibility of 97.7% without subtraction of accidentals.
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Rosfjord KM, Yang JKW, Dauler EA, Kerman AJ, Vikas Anant, Voronov BM, et al. Nanowire Single-photon detector with an integrated optical cavity and anti-reflection coating. Opt Express. 2006;14(2):527–34.
Abstract: We have fabricated and tested superconducting single-photon detectors and demonstrated detection efficiencies of 57% at 1550-nm wavelength and 67% at 1064 nm. In addition to the peak detection efficiency, a median detection efficiency of 47.7% was measured over 132 devices at 1550 nm. These measurements were made at 1.8K, with each device biased to 97.5% of its critical current. The high detection efficiencies resulted from the addition of an optical cavity and anti-reflection coating to a nanowire photodetector, creating an integrated nanoelectrophotonic device with enhanced performance relative to the original device. Here, the testing apparatus and the fabrication process are presented. The detection efficiency of devices before and after the addition of optical elements is also reported.
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Anant V, Kerman AJ, Dauler EA, Yang JKW, Rosfjord Kine M, Berggren KK. Optical properties of superconducting nanowire single-photon detectors. Opt Express. 2008;16(14):10750.
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Dauler E, Kerman A, Robinson B, Yang J, Voronov B, Goltsman G, et al. Photon-number-resolution with sub-30-ps timing using multi-element superconducting nanowire single photon detectors. J Modern Opt. 2009;56(2):364–73.
Abstract: A photon-number-resolving detector based on a four-element superconducting nanowire single photon detector is demonstrated to have sub-30-ps resolution in measuring the arrival time of individual photons. This detector can be used to characterize the photon statistics of non-pulsed light sources and to mitigate dead-time effects in high-speed photon counting applications. Furthermore, a 25% system detection efficiency at 1550 nm was demonstrated, making the detector useful for both low-flux source characterization and high-speed photon-counting and quantum communication applications. The design, fabrication and testing of this detector are described, and a comparison between the measured and theoretical performance is presented.
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Marsili F, Najafi F, Dauler E, Bellei F, Hu X, Csete M, et al. Single-photon detectors based on ultranarrow superconducting nanowires. Nano Lett. 2011;11(5):2048–2053.
Abstract: We report efficient single-photon detection (η = 20% at 1550 nm wavelength) with ultranarrow (20 and 30 nm wide) superconducting nanowires, which were shown to be more robust to constrictions and more responsive to 1550 nm wavelength photons than standard superconducting nanowire single-photon detectors, based on 90 nm wide nanowires. We also improved our understanding of the physics of superconducting nanowire avalanche photodetectors, which we used to increase the signal-to-noise ratio of ultranarrow-nanowire detectors by a factor of 4, thus relaxing the requirements on the read-out circuitry and making the devices suitable for a broader range of applications.
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Hu X, Dauler EA, Molnar RJ, Berggren KK. Superconducting nanowire single-photon detectors integrated with optical nano-antennae. Opt Express. 2011;19(1):17–31.
Abstract: Optical nano-antennae have been integrated with semiconductor lasers to intensify light at the nanoscale and photodiodes to enhance photocurrent. In quantum optics, plasmonic metal structures have been used to enhance nonclassical light emission from single quantum dots. Absorption and detection of single photons from free space could also be enhanced by nanometallic antennae, but this has not previously been demonstrated. Here, we use nano-optical transmission effects in a one-dimensional gold structure, combined with optical cavity resonance, to form optical nano-antennae, which are further used to couple single photons from free space into a 80-nm-wide superconducting nanowire. This antenna-assisted coupling enables a superconducting nanowire single-photon detector with 47% device efficiency at the wavelength of 1550 nm and 9-μm-by-9-μm active area while maintaining a reset time of only 5 ns. We demonstrate nanoscale antenna-like structures to achieve exceptional efficiency and speed in single-photon detection.
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