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Kawakami, A., Saito, S., & Hyodo, M. (2011). Fabrication of nano-antennas for superconducting Infrared detectors. IEEE Trans. Appl. Supercond., 21(3), 632–635.
Abstract: To improve the response performance of superconducting infrared detectors, we have developed a fabrication process for nano-antennas. A nano-antenna consists of a dipole antenna, and a superconducting thin film strip placed in the antenna's center. By measuring the transition temperature of the superconducting strips, we confirmed that their superconductivity maintained a good condition after the nano-antenna fabrication process. We also evaluated nano-antenna characteristics using Fourier transform infrared spectroscopy. The evaluated antenna length and width were respectively set at around 2400 nm and 400 nm, and the antennas were placed at intervals of several micrometers around the area of 1 mm2 . In an evaluation of spectral transmission characteristics, clear absorption caused by antenna effects was observed at around 1400 cm-1. High polarization dependencies were also observed.
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Lobanov, Y., Tong, E., Blundell, R., Hedden, A., Voronov, B., & Gol'tsman, G. (2011). Large-signal frequency response of an HEB mixer: from 300 MHz to terahertz. IEEE Trans. Appl. Supercond., 21(3), 628–631.
Abstract: We present a study of the large signal frequency response of an HEB mixer over a wide frequency range. In our experiments, we have subjected the HEB mixer to incident electromagnetic radiation from 0.3 GHz to 1 THz. The mixer element is an NbN film deposited on crystalline quartz. The mixer chip is mounted in a waveguide cavity, coupled to free space with a diagonal horn. At microwave frequencies, electromagnetic radiation is applied through the coaxial bias port of the mixer block. At higher frequencies the input signal passes via the diagonal horn feed. At each frequency, the incident power is varied and a family of I-V curves is recorded. From the curves we identify 3 distinct regimes of operation of the mixer separated by the phonon relaxation frequency and the superconducting energy gap frequency observed at about 3 GHz and 660 GHz respectively. In this paper, we will present observed curves and discuss the results of our experiment.
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Yang, J. K. W., Dauler, E., Ferri, A., Pearlman, A., Verevkin, A., Gol’tsman, G., et al. (2005). Fabrication development for nanowire GHz-counting-rate single-photon detectors. IEEE Trans. Appl. Supercond., 15(2), 626–630.
Abstract: We have developed a fabrication process for GHz-counting-rate, single-photon, high-detection-efficiency, NbN, nanowire detectors. We have demonstrated two processes for the device patterning, one based on the standard polymethylmethacrylate (PMMA) organic positive-tone electron-beam resist, and the other based on the newer hydrogen silsesquioxane (HSQ) negative-tone spin-on-glass resist. The HSQ-based process is simple and robust, providing high resolution and the prospect of high fill-factors. Initial testing results show superconductivity in the films, and suggest that the devices exhibit photosensitivity.
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Tretyakov, I., Ryabchun, S., Finkel, M., Maslennikov, S., Maslennikova, A., Kaurova, N., et al. (2011). Ultrawide noise bandwidth of NbN hot-electron bolometer mixers with in situ gold contacts. IEEE Trans. Appl. Supercond., 21(3), 620–623.
Abstract: We report a noise bandwidth of 7 GHz in the new generation of NbN hot-electron bolometer (HEB) mixers that are being developed for the space observatory Millimetron. The HEB receiver driven by a 2.5-THz local oscillator offered a noise temperature of 600 K in a 50-MHz final detection bandwidth. As the filter center frequency was swept this value remained nearly constant up to the cutoff frequency of the cryogenic amplifier at 7 GHz. We believe that such a low value of the noise temperature is due to reduced radio frequency (RF) loss at the interface between the superconducting film and the gold contacts. We have also performed gain bandwidth measurements at the superconducting transition on HEB mixers with various lengths and found them to be in excellent agreement with the results of the analytical and numerical models developed for the HEB mixer with both diffusion and phonon cooling of hot electrons.
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Gol'tsman, G. N., & Loudkov, D. N. (2003). Terahertz superconducting hot-electron bolometer mixers and their application in radio astronomy. Radiophys. Quant. Electron., 46(8/9), 604–617.
Abstract: We review the latest developments, research, and radioastronomy applications of hot-electron bolometer (HEB) mixers operated in the terahertz waveband. The physical principles of operation of terahertz HEB mixers are presented, their manufacturing from ultrathin NbN films, the main HEB-mixer parameters and their measurement techniques are discussed, and practical terahertz radioastronomy projects based on heterodyne receivers with HEB mixers are considered.
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Zhang, J., Pearlman, A., Slysz, W., Verevkin, A., Sobolewski, R., Wilsher, K., et al. (2003). A superconducting single-photon detector for CMOS IC probing. In Proc. 16-th LEOS (Vol. 2, pp. 602–603).
Abstract: In this paper, a novel, time-resolved, NbN-based, superconducting single-photon detector (SSPD) has been developed for probing CMOS integrated circuits (ICs) using photon emission timing analysis (PETA).
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Antipov, S. V., Vachtomin, Y. B., Maslennikov, S. N., Smirnov, K. V., Kaurova, N. S., Grishina, E. V., et al. (2004). Noise performance of quasioptical ultrathin NbN hot electron bolometer mixer at 2.5 and 3.8 THz. In Proc. 5-th MSMW (Vol. 2, pp. 592–594). Kharkov, Ukraine.
Abstract: To put space-based and airborne heterodyne instruments into operation at frequencies above 1 THz the superconducting NbN hot-electron bolometer (HEB) will be incorporated into heterodyne receiver as a mixer. At frequencies above 1.3 THz the sensitivity of the NbN HEB mixers outperform the one of the Schottky diodes and SIS-mixers, and the receiver noise temperature of the NbN HEB mixers increase with frequency. In this paper we present the results of the noise temperature measurements within one batch of NbN HEB mixers based on 3.5 mn thick superconducting NbN film grown on Si substrate with MgO buffer layer at the LO frequencies 2.5 THz and 3.8 THz.
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Milostnaya, I., Korneev, A., Tarkhov, M., Divochiy, A., Minaeva, O., Seleznev, V., et al. (2008). Superconducting single photon nanowire detectors development for IR and THz applications. J. Low Temp. Phys., 151(1-2), 591–596.
Abstract: We present our progress in the development of superconducting single-photon detectors (SSPDs) based on meander-shaped nanowires made from few-nm-thick superconducting films. The SSPDs are operated at a temperature of 2–4.2 K (well below T c ) being biased with a current very close to the nanowire critical current at the operation temperature. To date, the material of choice for SSPDs is niobium nitride (NbN). Developed NbN SSPDs are capable of single photon counting in the range from VIS to mid-IR (up to 6 μm) with a record low dark counts rate and record-high counting rate. The use of a material with a low transition temperature should shift the detectors sensitivity towards longer wavelengths. We present state-of-the art NbN SSPDs as well as the results of our recent approach to expand the developed SSPD technology by the use of superconducting materials with lower T c , such as molybdenum rhenium (MoRe). MoRe SSPDs first were made and tested; a single photon response was obtained.
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Jiang, L., Zhang, W., Yao, Q. J., Lin, Z. H., Li, J., Shi, S. C., et al. (2005). Characterization of a quasi-optical NbN superconducting hot-electron bolometer mixer. In Proc. PIERS (Vol. 1, pp. 587–590).
Abstract: In this paper, we report the performance of a quasi-optical NbN superconducting HEB (hot electron bolome-ter) mixer measured at 500 GHz. The quasi-optical NbN superconducting HEB mixer is cryogenically cooled bya 4-K close-cycled refrigerator. Its receiver noise temperature and conversion gain are thoroughly investigatedfor different LO pumping levels and dc biases. The lowest receiver noise temperature is found to be approxi-mately 1200 K, and reduced to about 445 K after correcting theloss of the measurement system. The stabilityof the mixer’s IF output power is also demonstrated.
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Gerecht, E., Musante, C. F., Wang, Z., Yngvesson, K. S., Mueller, E. R., Waldman, J., et al. (1996). Optimization of hot eleciron bolometer mixing efficiency in NbN at 119 micrometer wavelength. In Proc. 7th Int. Symp. Space Terahertz Technol. (pp. 584–600).
Abstract: We describe an investigation of a NbN HEB mixer for 2.5 THz. An intrinsic conversion loss of 23 dB has been measured with a two-laser measurement technique. The conversion loss was limited by the LO power available and is expected to decrease to 10 dB or less when sufficient LO power is available. For this initial experiment we used a prototype device which is directly coupled to the laser beams. We present results for a back-short technique that improves the optical coupling to the device and describe our progress for an antenna-coupled device with a smaller dimension. Based on our measured data for conversion loss and device output noise level, we predict that NbN HEB mixers will be capable of achieving DSB receiver noise temperatures of ten times the quantum noise limit in the THz range.
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Semenov, A. D., Nebosis, R. S., Gousev, Y. P., Heusinger, M. A., & Renk, K. F. (1995). Analysis of the nonequilibrium photoresponse of superconducting films to pulsed radiation by use of a two-temperature model. Phys. Rev. B, 52(1), 581–590.
Abstract: Photoresponse of a superconducting film in the resistive state to pulsed radiation has been studied in the framework of a model assuming that two different effective temperatures can be assigned to the quasiparticle and phonon nonequilibrium distributions. The coupled electron-phonon-substrate system is described by a system of time-dependent energy-balance differential equations for effective temperatures. An analytical solution of the system is given and calculated voltage transients are compared with experimental photoresponse signals taking into account the radiation pulse shape and the time resolution of the readout electronics. It is supposed that a resistive state (vortices, fluxons, network of intergrain junctions, hot spots, phase slip centers) provides an ultrafast connection between electron temperature changes and changes of the film resistance and thus plays a minor role in the temporal evolution of the response. In accordance with experimental observations a two-component response was revealed from simulations. The slower component corresponds to a bolometric mechanism while the fast component is connected with the relaxation of the electron temperature. Calculated photoresponse transients are presented for different ratios of the electron and phonon specific heat, radiation pulse durations and fluences, and frequency band passes of registration electronics. From the amplitude of the bolometric component we determine the radiation energy absorbed in a film. This enables us to reveal an intrinsic electron-phonon scattering time even if it is much shorter than the time resolution of readout electronics. We analyze experimental voltage transients for NbN, YBa2Cu3O7, and TlBa2Ca2Cu3O9 superconducting films and find the electron-phonon interaction times at the transition temperatures of 17, 2.5, and 1.8 ps, respectively. The values are in reasonable agreement with data of other experiments.
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Pearlman, A., Cross, A., Slysz, W., Zhang, J., Verevkin, A., Currie, M., et al. (2005). Gigahertz counting rates of NbN single-photon detectors for quantum communications. IEEE Trans. Appl. Supercond., 15(2), 579–582.
Abstract: We report on the GHz counting rate and jitter of our nanostructured superconducting single-photon detectors (SSPDs). The devices were patterned in 4-nm-thick and about 100-nm-wide NbN meander stripes and covered a 10-/spl mu/m/spl times/10-/spl mu/m area. We were able to count single photons at both the visible and infrared telecommunication wavelengths at rates of over 2 GHz with a timing jitter of below 18 ps. We also present the model for the origin of the SSPD switching dynamics and jitter, based on the time-delay effect in the phase-slip-center formation mechanism during the detector photoresponse process. With further improvements in our readout electronics, we expect that our SSPDs will reach counting rates of up to 10 GHz. An integrated quantum communications receiver based on two fiber-coupled SSPDs and operating at 1550-nm wavelength is also presented.
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Hubers, H. - W., Semenov, A., Richter, H., Schwarz, M., Gunther, B., Smirnov, K., et al. (2004). Heterodyne receiver for 3-5 THz with hot-electron bolometer mixer. In J. Zmuidzinas, W. S. Holland, & S. Withington (Eds.), Proc. SPIE (Vol. 5498, pp. 579–586). SPIE.
Abstract: Heterodyne receivers for applications in astronomy and planetary research need quantum limited sensitivity. In instruments which are currently build for SOFIA and Herschel superconducting hot electron bolometers (HEB) will be used to achieve this goal at frequencies above 1.4 THz. The local oscillator and the mixer are the most critical components for a heterodyne receiver operating at 3-5 THz. The design and performance of an optically pumped THz gas laser optimized for this frequency band will be presented. In order to optimize the performance for this frequency hot electron bolometer mixers with different in-plane dimensions and logarithmic-spiral feed antennas have been investigated. Their noise temperatures and beam patterns were measured. Above 3 THz the best performance was achieved with a superconducting bridge of 2.0 x 0.2 μm2 incorporated in a logarithmic spiral antenna. The DSB noise temperatures were 2700 K, 4700 K and 6400 K at 3.1 THz, 4.3 THz and 5.2 THz, respectively. The results demonstrate that the NbN HEB is very well suited as a mixer for THz heterodyne receivers up to at least 5 THz.
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Gol’tsman, G., Okunev, O., Chulkova, G., Lipatov, A., Dzardanov, A., Smirnov, K., et al. (2001). Fabrication and properties of an ultrafast NbN hot-electron single-photon detector. IEEE Trans. Appl. Supercond., 11(1), 574–577.
Abstract: A new type of ultra-high-speed single-photon counter for visible and near-infrared wavebands based on an ultrathin NbN hot-electron photodetector (HEP) has been developed. The detector consists of a very narrow superconducting stripe, biased close to its critical current. An incoming photon absorbed by the stripe produces a resistive hotspot and causes an increase in the film’s supercurrent density above the critical value, leading to temporary formation of a resistive barrier across the device and an easily measurable voltage pulse. Our NbN HEP is an ultrafast (estimated response time is 30 ps; registered time, due to apparatus limitations, is 150 ps), frequency unselective device with very large intrinsic gain and negligible dark counts. We have observed sequences of output pulses, interpreted as single-photon events for very weak laser beams with wavelengths ranging from 0.5 /spl mu/m to 2.1 /spl mu/m and the signal-to-noise ratio of about 30 dB.
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Korneev, A., Matvienko, V., Minaeva, O., Milostnaya, I., Rubtsova, I., Chulkova, G., et al. (2005). Quantum efficiency and noise equivalent power of nanostructured, NbN, single-photon detectors in the wavelength range from visible to infrared. IEEE Trans. Appl. Supercond., 15(2), 571–574.
Abstract: We present our studies on the quantum efficiency (QE) and the noise equivalent power (NEP) of the latest-generation, nanostructured, superconducting, single-photon detectors (SSPDs) in the wavelength range from 0.5 to 5.6 /spl mu/m, operated at temperatures in the 2.0- to 4.2-K range. Our detectors are designed as 4-nm-thick and 100-nm-wide NbN meander-shaped stripes, patterned by electron-beam lithography and cover a 10/spl times/10-/spl mu/m/sup 2/ active area. The best-achieved QE at 2.0 K for 1.55-/spl mu/m photons is 17%, and QE for 1.3-/spl mu/m infrared photons reaches its saturation value of /spl sim/30%. The SSPD NEP at 2.0 K is as low as 5/spl times/10/sup -21/ W/Hz/sup -1/2/. Our nanostructured SSPDs, operated at 2.0 K, significantly outperform their semiconducting counterparts, and, together with their GHz counting rate and picosecond timing jitter, they are devices-of-choice for practical quantum key distribution systems and free-space (even interplanetary) quantum optical communications.
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