Okunev, O., Smirnov, K., Chulkova, G., Korneev, A., Lipatov, A., Gol'tsman, G., et al. (2002). Ultrafast NBN hot-electron single-photon detectors for electronic applications. In Abstracts 8-th IUMRS-ICEM.
Abstract: We present a new, simple to manufacture, single-photon detector (SPD), which can work from ultraviolet to near-infrared wavelengths of optical radiation and combines high speed of operation, high quantum efficiency (QE), and very low dark counts. The devices are superconducting and operate at temperature below 5 K. The physics of operation of our SPD is based on formation of a photon-induced resistive hotspot and subsequent appearance of a transient resistive barrier across an ultrathin and submicron-wide superconductor.
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Semenov, A., Hübers, H. - W., Engel, A., & Gol'tsman, G. N. (2002). Background limited superconducting quantum detector for astronomy. In NASA/ADS.
Abstract: We present the concept of the superconducting quantum detector for astronomy. Response to a single absorbed photon appears due to successive formation of a normal spot and phase-slip-centers in a narrow strip carrying sub-critical supercurrent. The detector simultaneously has a moderate energy resolution and a variable cut-off wavelength depending on both the material used and operation conditions. We simulated performance of the background-limited direct detector having the 100- micrometer cut-off wavelength. Low dark count rate will allow to realize 10-21 W Hz-1/2 noise equivalent power at 4 K background radiation. The intrinsic recovery time of the counter is rather determined by diffusion of nonequilibrium electrons, thus, thermal fluctuations do not hamper energy resolution of the detector. Provided an appropriate readout technique, the resolution should be better than 1/20 at 50- micrometer wavelength. Planar layout and relatively simple technology favor integration of the detector into an array.
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Verevkin, A., Gershenzon, E. M., Gol'tsman, G. N., Ptitsina, N. G., Chulkova, G. M., Smirnov, K. S., et al. (2002). Direct measurements of energy relaxation times in two-dimensional structures under quasi-equilibrium conditions. In Mater. Sci. Forum (Vol. 384-3, pp. 107–116).
Abstract: A new microwave technique was successfully applied for direct studies of energy relaxation times in two-dimensional AlGaAs/GaAs structures under quasi-equilibrium conditions in the nanosecond and picosecond time scale. We report our results of energy relaxation time measurements in the temperature range 1.6-50 K, in quantum Hall effect regime in magnetic fields up to 4 T.
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Verevkin, A., Xu, Y., Zheng, X., Williams, C., Sobolewski, R., Okunev, O., et al. (2001). Superconducting NbN-based ultrafast hot-electron single-photon detector for infrared range. In Proc. 12th Int. Symp. Space Terahertz Technol. (pp. 462–468).
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Gol'tsman, G., Semenov, A., Smirnov, K., & Voronov, B. (2001). Background limited quantum superconducting detector for submillimeter wavelengths. In Proc. 12th Int. Symp. Space Terahertz Technol. (pp. 469–475).
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Xu, Y., Zheng, X., Williams, C., Verevkin, A., Sobolewski, R., Chulkova, G., et al. (2001). Ultrafast superconducting hot-electron single-photon detector. In CLEO (345).
Abstract: Summary form only given. The current most-pressing need is to develop a practical, GHz-range counting single-photon detector, operational at either 1.3-/spl mu/m or 1.55-/spl mu/m radiation wavelength, for novel quantum communication and quantum cryptography systems. The presented solution of the problem is to use an ultrafast hot-electron photodetector, based on superconducting thin-film microstructures. This type of device is very promising, due to the macroscopic quantum nature of superconductors. Very fast response time and the small, (meV range) value of the superconducting energy gap characterize the superconductor, leading to the efficient avalanche process even for infrared photons.
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Yagoubov, P., Hübers, H. - W., Gol’tsman, G., Semenov, A., Gao, J., Hoogeveen, R., et al. (2001). Hot-electron bolometer mixers – technology for far-infrared heterodyne instruments in future atmospheric chemistry missions. In S. Buehler, & Berlin (Eds.), Proc. 3rd Int. Symp. Submillimeter Wave Earth Observation From Space (pp. 57–69). Logos-Verlag.
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Hübers, H. - W., Semenov, A., Schubert, J., Gol'tsman, G., Voronov, B., & Gershenzon, E. (2000). Performance of the phonon-cooled hot-electron bolometric mixer between 0.7 THz and 5.2 THz. In Proc. 8-th Int. Conf. on Terahertz Electronics (pp. 117–119).
Abstract: We report on the phonon cooled NbN hot electron bolometer as mixer in the terahertz frequency range. Its hybrid antenna consists of a hyperhemispheric silicon lens and a logarithmic-spiral feed antenna. Noise temperatures have been measured between 0.7 THz and 5.2 THz. A quarter wavelength layer of Parylene works as antireflection coating for the silicon lens and reduces the noise temperature by about 30. It was found that the antenna pattern at 2.5 THz is determined by the feed antenna and not by the diameter of the lens.
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Huebers, H. - W., Semenov, A., Schubert, J., Gol’tsman, G. N., Voronov, B. M., Gershenzon, E. M., et al. (2000). NbN hot-electron bolometer as THz mixer for SOFIA. In R. K. Melugin, & H. - P. Roeser (Eds.), Proc. SPIE (Vol. 4014, pp. 195–202). SPIE.
Abstract: Heterodyne receivers for applications in astronomy need quantum limited sensitivity. We have investigated phonon- cooled NbN hot electron bolometric mixers in the frequency range from 0.7 THz to 5.2 THz. The devices were 3.5 nm thin films with an in-plane dimension of 1.7 X 0.2 micrometers 2 integrated in a complementary logarithmic spiral antenna. The best measured DSB receiver noise temperatures are 1300 K (0.7 THz), 2000 K (1.4 THz), 2100 K (1.6 THz), 2600 K (2.5 THz), 4000 K (3.1 THz), 5600 K (4.3 THz), and 8800 K (5.2 THz). The sensitivity fluctuation, the long term stability, and the antenna pattern were measured. The results demonstrate that this mixer is very well suited for GREAT, the German heterodyne receiver for SOFIA.
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Darula, M., Semenov, A. D., Hübers, H. - W., & Schubert, J. (2000). Quasioptical high-Tc superconductor Josephson mixer at terahertz frequencies. In Proc. 11th Int. Symp. Space Terahertz Technol. (515).
Abstract: Mixers based on Josephson junctions from conventional superconductor materials have demonstrated excellent performance at subgap frequencies. The advantages of Josephson mixers are low optimal power of the local oscillator and large intermediate frequency bandwidth but their noise temperature increases dramatically at frequencies corresponding to the energy gap of the superconductor, which is typically below 1 THz for widely used materials. The large energy gap of oxide superconductors makes them promising candidates for development of terahertz Josephson mixers. Here we report on experimental study of the quasioptical mixer utilizing bicrystal Josephson junction from high-transition-temperature YBa 2 Cu 3 O 7-δ film. Junctions with a width of 2 µm were fabricated from 100 nm thick laser ablated films on bicrystal MgO substrates and had the and the J C R n product of about 2 mV at 4.2 K. The planar complementary logarithmic spiral antenna incorporated into co-planar waveguide was patterned from 200 nm thick gold film thermally evaporated in situ on top of the YBa 2 Cu 3 O 7-δ film. The mixer chip was clamped to the extended hemispherical silicon lens. Performance of the mixer was investigated at 4.5 K bath temperature. We used FIR laser as a local oscillator at frequencies 0.698 and 2.52 THz. System noise temperature (DSB) was determined from Y-factor measured with 300 K and 77 K loads. At 0.698 THz the lowest noise temperature 1750 K was observed when the mixer was biased with the fixed current to the region in the vicinity of either the first Shapiro step or the critical current. Between these two bias points the noise temperature increased to ≈ 20000 K. As function of the local oscillator power the noise temperature reached the minimum when the critical current was suppressed to the half of its equilibrium value. Power of the local oscillator absorbed by the mixer at optimal operation was of the order 100 nW. The present design of our antenna limits the upper operation frequency to the value of 1.8 THz. Nevertheless, we clearly observed Shapiro steps at the frequency 2.52 THz. Bearing in mind an improved design of the antenna, we estimate the 3000 K DSB noise temperature at this frequency.
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