|
|
Rasulova, G. K., Brunkov, P. N., Pentin, I. V., Kovalyuk, V. V., Gorshkov, K. N., Kazakov, A. Y., et al. (2011). Mutual synchronization of two coupled self-oscillators based on GaAs/AlGaAs superlattices. Tech. Phys., 56(6), 826–830.
Abstract: The interaction of self-oscillators based on 30-period weakly coupled GaAs/AlGaAs superlattices is studied. The action of one self-oscillator on the other was observed for a constant bias voltage in the absence of generation of self-sustained oscillations in one of the oscillators. It is shown that induced oscillations in a forced oscillator appear due to excitation of oscillations in the system of coupled oscillators forming the electric-field domain wall at the frequency of one of the higher harmonics of a forcing oscillation.
|
|
|
|
Goltsman, G., Korneev, A., Izbenko, V., Smirnov, K., Kouminov, P., Voronov, B., et al. (2004). Nano-structured superconducting single-photon detectors. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 520(1-3), 527–529.
Abstract: NbN detectors, formed into meander-type, 10×10-μm2 area structures, based on ultrathin (down to 3.5-nm thickness) and nanometer-width (down to below 100 nm) NbN films are capable of efficiently detecting and counting single photons from the ultraviolet to near-infrared optical wavelength range. Our best devices exhibit QE >15% in the visible range and ∼10% in the 1.3–1.5-μm infrared telecommunication window. The noise equivalent power (NEP) ranges from ∼10−17 W/Hz1/2 at 1.5 μm radiation to ∼10−19 W/Hz1/2 at 0.56 μm, and the dark counts are over two orders of magnitude lower than in any semiconducting competitors. The intrinsic response time is estimated to be <30 ps. Such ultrafast detector response enables a very high, GHz-rate real-time counting of single photons. Already established applications of NbN photon counters are non-invasive testing and debugging of VLSI Si CMOS circuits and quantum communications.
|
|
|
|
Rosfjord, K. M., Yang, J. K. W., Dauler, E. A., Kerman, A. J., Vikas Anant, Voronov, B. M., et al. (2006). Nanowire Single-photon detector with an integrated optical cavity and anti-reflection coating. Opt. Express, 14(2), 527–534.
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.
|
|
|
|
Baselmans, J. J. A., Hajenius, M., Gao, J. R., Baryshev, A., Kooi, J., Klapwijk, T. M., et al. (2005). NbN hot electron bolometer mixers: sensitivity, LO power, direct detection and stability. IEEE Trans. Appl. Supercond., 15(2), 484–489.
Abstract: We demonstrate that the performance of NbN lattice cooled hot electron bolometer mixers depends strongly on the interface quality between the bolometer and the contact structure. Both the receiver noise temperature and the gain bandwidth can be improved by a factor of 2 by cleaning the interface and adding an additional superconducting interlayer to the contact pad. Using this we obtain a double sideband receiver noise temperature of 950 K at 2.5 THz and 4.3 K, using a 0.4/spl times/4 /spl mu/m HEB mixer with a spiral antenna. At the same bias point, we obtain an IF gain bandwidth of 6 GHz. To comply with current demands on THz mixers for use in space based receivers we reduce the device size to 0.15/spl times/1 /spl mu/m and use a twin slot antenna. We report measurements of the noise temperature, LO power requirement, stability and the direct detection effect, using a mixer with a 1.6 THz twin slot antenna and a 1.462 THz solid state LO source with calibrated output power.
|
|
|
|
Kroug, M., Cherednichenko, S., Merkel, H., Kollberg, E., Voronov, B., Gol'tsman, G., et al. (2001). NbN hot electron bolometric mixers for terahertz receivers. IEEE Trans. Appl. Supercond., 11(1), 962–965.
Abstract: Sensitivity and gain bandwidth measurements of phonon-cooled NbN superconducting hot-electron bolometer mixers are presented. The best receiver noise temperatures are: 700 K at 1.6 THz and 1100 K at 2.5 THz. Parylene as an antireflection coating on silicon has been investigated and used in the optics of the receiver. The dependence of the mixer gain bandwidth (GBW) on the bias voltage has been measured. Starting from low bias voltages, close to operating conditions yielding the lowest noise temperature, the GBW increases towards higher bias voltages, up to three times the initial value. The highest measured GBW is 9 GHz within the same bias range the noise temperature increases by a factor of two.
|
|
|
|
Gerecht, E., Musante, C. F., Zhuang, Y., Yngvesson, K. S., Gol’tsman, G. N., Voronov, B. M., et al. (1999). NbN hot electron bolometric mixerss—a new technology for low-noise THz receivers. IEEE Trans. Appl. Supercond., 47(12), 2519–2527.
Abstract: New advances in hot electron bolometer (HEB) mixers have recently resulted in record-low receiver noise temperatures at terahertz frequencies. We have developed quasi-optically coupled NbN HEB mixers and measured noise temperatures up to 2.24 THz, as described in this paper. We project the anticipated future performance of such receivers to have even lower noise temperature and local-oscillator power requirement as well as wider gain and noise bandwidths. We introduce a proposal for integrated focal plane arrays of HEB mixers that will further increase the detection speed of terahertz systems.
|
|
|
|
Gol'tsman, G. N., Karasik, B. S., Okunev, O. V., Dzardanov, A. L., Gershenzon, E. M., Ekstrom, H., et al. (1995). NbN hot electron superconducting mixers for 100 GHz operation. IEEE Trans. Appl. Supercond., 5(2), 3065–3068.
Abstract: NbN is a promising superconducting material for hot-electron superconducting mixers with an IF bandwidth larger than 1 GHz. In the 1OO GHz frequency range, the following parameters were obtained for 50 /spl Aring/ thick NbN films at 4.2 K: receiver noise temperature (DSB) /spl sim/1000 K; conversion loss /spl sim/10 dB; IF bandwidth /spl sim/1 GHz; and local oscillator power /spl sim/1 /spl mu/W. An increase of the critical current of the NbN film, increased working temperature, and a better mixer matching may allow a broader IF bandwidth up to 2 GHz, reduced conversion losses down to 3-5 dB and a receiver noise temperature (DSB) down to 200-300 K.
|
|
|
|
Lobanov, Y., Shcherbatenko, M., Finkel, M., Maslennikov, S., Semenov, A., Voronov, B. M., et al. (2015). NbN hot-electron-bolometer mixer for operation in the near-IR frequency range. IEEE Trans. Appl. Supercond., 25(3), 2300704 (1 to 4).
Abstract: Traditionally, hot-electron-bolometer (HEB) mixers are employed for THz and “super-THz” heterodyne detection. To explore the near-IR spectral range, we propose a fiber-coupled NbN film based HEB mixer. To enhance the incident-light absorption, a quasi-antenna consisting of a set of parallel stripes of gold is used. To study the antenna effect on the mixer performance, we have experimentally studied a set of devices with different size of the Au stripe and spacing between the neighboring stripes. With use of the well-known isotherm technique we have estimated the absorption efficiency of the mixer, and the maximum efficiency has been observed for devices with the smallest pitch of the alternating NbN and NbN-Au stripes. Also, a proper alignment of the incident Eâƒ<2014>-field with respect to the stripes allows us to improve the coupling further. Studying IV-characteristics of the mixer under differently-aligned Eâƒ<2014>-field of the incident radiation, we have noticed a difference in their shape. This observation suggests that a difference exists in the way the two waves with orthogonal polarizations parallel and perpendicular Eâƒ<2014>-field to the stripes heat the electrons in the HEB mixer. The latter results in a variation in the electron temperature distribution over the HEB device irradiated by the two waves.
|
|
|
|
Korneev, A., Korneeva, Y., Florya, I., Voronov, B., & Goltsman, G. (2012). NbN nanowire superconducting single-photon detector for mid-infrared. Phys. Procedia, 36, 72–76.
Abstract: Superconducting single-photon detectors (SSPD) is typically 100 nm-wide supercondiucting strip in a shape of meander made of 4-nm-thick film. To reduce response time and increase voltage response a parallel connection of the strips was proposed. Recently we demonstrated that reduction of the strip width improves the quantum effciency of such a detector at wavelengths longer than 1.5 μm. Being encourage by this progress in quantum effciency we improved the fabrication process and made parallel-wire SSPD with 40-nm-wide strips covering total area of 10 μm x 10 μm. In this paper we present the results of the characterization of such a parallel-wire SSPD at 10.6 μm wavelength and demonstrate linear dependence of the count rate on the light power as it should be in case of single-photon response.
|
|
|
|
Smirnov, K., Divochiy, A., Vakhtomin, Y., Morozov, P., Zolotov, P., Antipov, A., et al. (2018). NbN single-photon detectors with saturated dependence of quantum efficiency. Supercond. Sci. Technol., 31(3), 035011 (1 to 8).
Abstract: The possibility of creating NbN superconducting single-photon detectors with saturated dependence of quantum efficiency (QE) versus normalized bias current was investigated. It was shown that the saturation increases for the detectors based on finer films with a lower value of Rs300/Rs20. The decreasing of Rs300/Rs20 was related to the increasing influence of quantum corrections to conductivity of superconductors and, in turn, to the decrease of the electron diffusion coefficient. The best samples have a constant value of system QE 94% at Ib/Ic ~ 0.8 and wavelength 1310 nm.
|
|
