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Hovenier J.N., Adam A.J.L., Kašalynas I., Gao J.R., Klaassen T.O., Baryshev A., et al. (2006). Phase-locking on the beat signal of a two-mode 2.7 terahertz metal-metal quantum cascade laser. In Proc. Symp. IEEE/LEOS Benelux Chapter (pp. 125–128).
Abstract: We have studied the linewidth and phase-locking of a 2.7 THz quantum cascade laser by using a superconducting bolometer mixer. The 8 GHz beat signal is compared with a microwave reference with a feedback to the laser bias current. Phase locking has been demonstrated, resulting in an extremely narrow beat linewidth of less than 10 Hz. Under frequency-stabilization conditions we find that the line profile is virtually Lorentzian with a long-term minimum linewidth of the THz modes of about 6.3 kHz. Temperature dependent measurements suggestthat this linewidthdoes not approach the Schawlow-Townes limit.
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Chulkova, G., Milostnaya, I., Tarkhov, M., Korneev, A., Minaeva, O., Voronov, B., et al. (2006). Superconducting single-photon nanostructured detectors for advanced optical applications. In Proc. Symposium on Photonics Technologies for 7th Framework Program (Vol. 400).
Abstract: We present superconducting single-photon detectors (SSPDs) based on NbN thin-film nanostructures and operated at liquid helium temperatures. The SSPDs are made of ultrathin NbN films (2.5-4 nm thick, Tc= 9-11K) as meander-shaped nanowires covering the area of 10× 10 µm2. Our detectors are operated at the temperature well below the critical temperature Tc and are DC biased by a current Ib close to the meander critical current Ic. The operation principle of the detector is based on the use of the resistive region in a narrow ultra-thin superconducting stripe upon the absorption of an incident photon. The developed devices demonstrate high sensitivity and response speed in a broadband range from UV to mid-IR (up to 6 µm), making them very attractive for advanced optical technologies, which require efficient detectors of single quanta and low-density optical radiation.
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Вахтомин, Ю. Б., Антипов, С. В., Масленников, С. Н., Смирнов, К. В., Поляков, С. Л., Чжан, В., et al. (2006). Квазиоптические смесители терагерцового диапазона на основе эффекта разогрева электронов в тонких пленках NbN. In Proc. 16th Int. Crimean Microwave and Telecommunication Technology (Vol. 2, pp. 688–689).
Abstract: Представлены результаты измерения рактеристик смесителей на эффекте разогрева электронов в тонких сверхпроводниковых пленках NbN. Смесители были изготовлены на основе пленок NbN толщиной 2-3.5 нм осажденных на кремниевую подложку с буферным подсло- ем MgO. Смесительный элемент согласовывался с планар- ной логопериодической спиральной антенной. Лучшее зна- чение шумовой температуры приемника на основе NbN смесителя составило 1300 К и 3100 К на частотах гетеро- дина 2.5 TГц и 3.8 ТГц, соответственно. Максимальное зна- чение полосы преобразования, измеренной на частоте 900 |Ц, достигло значения 5.2 ГГц для смесителя изготовлен- ного из NbN пленки толщиной 2 нм. Оптимальная мощность Представлены результаты измерения ха- гетеродинного источника составила 1-3 мкВт для смесите- лей с различным объемом смесительного элемента.
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Goltsman, G. N. (2006). Submillimeter superconducting receivers for astronomy, atmospheric studies and other applications. In 31nd IRMW / 14th ICTE (177).
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Hadfield, R. H., Habif, J. L., Schlafer, J., Schwall, R. E., & Nam, S. W. (2006). Quantum key distribution at 1550 nm with twin superconducting single-photon detectors. Appl. Phys. Lett., 89(24), 241129.
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Rodriguez-Morales, F., Zannoni, R., Nicholson, J., Fischetti, M., Yngvesson, K. S., & Appenzeller, J. (2006). Direct and heterodyne detection of microwaves in a metallic single wall carbon nanotube. Appl. Phys. Lett., 89(8), 083502.
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Stevens, M., Hadfield, R., Schwall, R., Nam, S. W., Mirin, R., & Gupta, J. (2006). Fast lifetime measurements of infrared emitters using a low-jitter superconduct- ing single-photon detector. Appl. Phys. Lett., 89, 031109.
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Walther, C., Scalari, G., Faist, J., Beere, H., & Ritchie, D. (2006). Low frequency terahertz quantum cascade laser operating from 1.6 to 1.8 THz. Appl. Phys. Lett., 89, 231121(1–3).
Abstract: The authors report a GaAs/Al0.1Ga0.9As quantum cascade laser based on a bound-to-continuum transition optimized for low frequency operation. High tunability of the gain curve is achieved by the Stark effect and laser emission is measured between 1.6 and 1.8 THz. Pulsed mode operation up to 95 K and continuous wave operation up to 80 K are reported. The dynamical range in current is as high as 43%.
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Słysz, W., Węgrzecki, M., Bar, J., Grabiec, P., Górska, M., Zwiller, V., et al. (2006). Fiber-coupled single-photon detectors based on NbN superconducting nanostructures for practical quantum cryptography and photon-correlation studies. Appl. Phys. Lett., 88(26), 261113 (1 to 3).
Abstract: We have fabricated and tested a two-channel single-photon detector system based on two fiber-coupled superconducting single-photon detectors (SSPDs). Our best device reached the system quantum efficiency of 0.3% in the 1540-nm telecommunication wavelength with a fiber-to-detector coupling factor of about 30%. The photoresponse consisted of 2.5-ns-wide voltage pulses with a rise time of 250ps and timing jitter below 40ps. The overall system response time, measured as a second-order, photon cross-correlation function, was below 400ps. Our SSPDs operate at 4.2K inside a liquid-helium Dewar, but their optical fiber inputs and electrical outputs are at room temperature. Our two-channel detector system should find applications in practical quantum cryptography and in antibunching-type quantum correlation measurements.
The authors would like to thank Dr. Marc Currie for his assistance in early time-resolved photoresponse measurements and Professor Atac Imamoglu for his support. This work was supported by the Polish Ministry of Science under Project No. 3 T11B 052 26 (Warsaw), RFBR 03-02-17697 and INTAS 03-51-4145 grants (Moscow), CRDF Grant No. RE2-2531-MO-03 (Moscow), RE2-2529-MO-03 (Moscow and Rochester), and US AFOSR FA9550-04-1-0123 (Rochester). Additional funding was provided by the grants from the MIT Lincoln Laboratory and BBN Technologies Corp.
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Kerman, A. J., Dauler, E. A., Keicher, W. E., Yang, J. K. W., Berggren, K. K., Gol’tsman, G., et al. (2006). Kinetic-inductance-limited reset time of superconducting nanowire photon counters. Appl. Phys. Lett., 88(11), 111116 (1 to 3).
Abstract: We investigate the recovery of superconducting NbN-nanowire photon counters after detection of an optical pulse at a wavelength of 1550nm, and present a model that quantitatively accounts for our observations. The reset time is found to be limited by the large kinetic inductance of these nanowires, which forces a tradeoff between counting rate and either detection efficiency or active area. Devices of usable size and high detection efficiency are found to have reset times orders of magnitude longer than their intrinsic photoresponse time.
The authors acknowledge D. Oates and W. Oliver (MIT Lincoln Laboratory), S.W. Nam, A. Miller, and R. Hadfield (NIST) and R. Sobolewski, A. Pearlman, and A. Verevkin (University of Rochester) for helpful discussions and technical assistance. This work made use of MIT’s shared scanning-electron-beam-lithography facility in the Research Laboratory of Electronics. This work is sponsored by the United States Air Force under Air Force Contract No. FA8721-05-C-0002. Opinions, interpretations, recommendations and conclusions are those of the authors and are not necessarily endorsed by the United States Government.
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