Dorenbos, S. N., Heeres, R. W., Driessen, E. F. C., & Zwiller, V. (2011). Efficient and robust fiber coupling of superconducting single photon detectors. arXiv, , 6.
Abstract: We applied a recently developed fiber coupling technique to superconducting single photon detectors (SSPDs). As the detector area of SSPDs has to be kept as small as possible, coupling to an optical fiber has been either inefficient or unreliable. Etching through the silicon substrate allows fabrication of a circularly shaped chip which self aligns to the core of a ferrule terminated fiber in a fiber sleeve. In situ alignment at cryogenic temperatures is unnecessary and no thermal stress during cooldown, causing misalignment, is induced. We measured the quantum efficiency of these devices with an attenuated tunable broadband source. The combination of a lithographically defined chip and high precision standard telecommunication components yields near unity coupling efficiency and a system detection efficiency of 34% at a wavelength of 1200 nm. This quantum efficiency measurement is confirmed by an absolute efficiency measurement using correlated photon pairs (with $\lambda$ = 1064 nm) produced by spontaneous parametric down-conversion. The efficiency obtained via this method agrees well with the efficiency measured with the attenuated tunable broadband source.
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Edlmayr, V., Harzer, T. P., Hoffmann, R., Kiener, D., Scheu, C., & Mitterer, C. (2011). Effects of thermal annealing on the microstructure of sputtered Al2O3 coatings. J. Vac. Sci. Technol. A, 29(4), 8.
Abstract: The morphology and microstructure of Al2O3 thin films deposited by pulsed direct current magnetron sputtering were studied in the as-grown state and after vacuum annealing at 1000 °C for 12 h using transmission electron microscopy. For the coating deposited under low ion bombardment conditions, the film consists of small γ- and/or δ-Al2O3 grains embedded in an amorphous matrix. The grain size at the region close to the interface to the substrate was much larger than that of the remaining layer. Growth of the γ-Al2O3 phase is promoted during annealing but no transformation to α-Al2O3 was detected. For high-energetic growth conditions, clear evidence for γ-Al2O3 formation was found in the upper part of the coating with grain size much larger than for low-energetic growth, but the film was predominately amorphous at the interface region. Annealing resulted in the transformation of γ-Al2O3 to α-Al2O3, while the mainly amorphous part crystallized to γ-Al2O3.
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Mazin, B. A., Bumble, B., Meeker, S. R., O'Brien, K., McHugh, S., & Langman, E. (2011). A superconducting focal plane array for ultraviolet, optical, and near-infrared astrophysics. arXiv, , 9.
Abstract: Microwave Kinetic Inductance Detectors, or MKIDs, have proven to be a powerful cryogenic detector technology due to their sensitivity and the ease with which they can be multiplexed into large arrays. A MKID is an energy sensor based on a photon-variable superconducting inductance in a lithographed microresonator, and is capable of functioning as a photon detector across the electromagnetic spectrum as well as a particle detector. Here we describe the first successful effort to create a photon-counting, energy-resolving ultraviolet, optical, and near infrared MKID focal plane array. These new Optical Lumped Element (OLE) MKID arrays have significant advantages over semiconductor detectors like charge coupled devices (CCDs). They can count individual photons with essentially no false counts and determine the energy and arrival time of every photon with good quantum efficiency. Their physical pixel size and maximum count rate is well matched with large telescopes. These capabilities enable powerful new astrophysical instruments usable from the ground and space. MKIDs could eventually supplant semiconductor detectors for most astronomical instrumentation, and will be useful for other disciplines such as quantum optics and biological imaging.
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Ozhegov, R. V., Gorshkov, K. N., Gol'tsman, G. N., Kinev, N. V., & Koshelets, V. P. (2011). The stability of a terahertz receiver based on a superconducting integrated receiver. Supercond. Sci. Technol., 24(3), 035003.
Abstract: We present the results of stability testing of a terahertz radiometer based on a superconducting receiver with a SIS tunnel junction as the mixer and a flux-flow oscillator as the local oscillator. In the continuum mode, the receiver with a noise temperature of 95 K at 510 GHz measured over the intermediate frequency (IF) passband of 4-8 GHz offered a noise equivalent temperature difference of 10 ± 1 mK at an integration time of 1 s. We offer a method to significantly increase the integration time without the use of complex measurement equipment. The receiver observed a strong signal over a final detection bandwidth of 4 GHz and offered an Allan time of 5 s.
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Флоря, И. Н., Корнеева, Ю. П., Корнеев, А. А., & Гольцман, Г. Н. (2011). Сверхпроводниковый однофотонный детектор для среднего инфракрасного диапазона на основе узких параллельных полосок. Труды МФТИ, 3(2), 14–17.
Abstract: Мы рассматриваем ультрабыстрый сверхпроводниковый однофотонный детектор (SSPD). SSPD представляет собой тонкопленочную наноструктуру — очень узкую и длинную полоску сверхпроводника, изогнутую в виде меандра, изготовленную из пленки NbN толщиной 4 нм, нанесенной на сапфировую подложку. SSPD хорошо сопрягается с оптоволокном и легко может быть интегрирован в полностью готовую для работы приемную систему. В стремлении продвинуться в средний ИК диапозон нам удалось разработать SSPD в виде параллельно соединенных полосок с шириной полоски всего 50 нм и сохранить при этом сверхпроводящие свойства. Эти детекторы показывают более чем на порядок большую чувствительность на длине волны 3;5 мкм, чем SSPD в виде меандра. Полученные результаты открывают путь к эффективным детекторам среднего ИК-диапазона, обладающим скоростью счета свыше 1 ГГц.
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