|
|
Baselmans, J. J. A., Hajenius, M., Gao, J. R., Klapwijk, T. M., de Korte, P. A. J., Voronov, B., et al. (2003). Noise performance of NbN hot electron bolometer mixers at 2.5 THz and its dependence on the contact resistance. In Proc. 14th Int. Symp. Space Terahertz Technol. (pp. 11–19).
Abstract: NbN hot electron bolometer mixers (HEBM) are at this moment the best heterodyne receivers for frequencies above 1 Thz. However, the fabrication procedure of these devices is such that the quality of the interface between the NbN superconducting film and the contact structure is not under good control. The result is a low transparency interface between the bolometer itself and the contact/antenna structure. In this paper we report a detailed experimental study on a novel idea to increase the transparency of this interface. This leads to a record sensitivity and more reproducible performance. We compare identical bolometers, coupled with a spiral antenna, with different NbN bolometer-contact pad interfaces. We find that cleaning the NbN interface alone results in an increase in the noise temperature. However, cleaning the NbN interface and adding a thin additional superconductor prior to the gold contact deposition improves the noise temperature of the HEBm with more than a factor of 2. A device with a contact pad on top of an in-situ cleaned NbN film consisting of 10 nm of NbTiN and 40 nm of gold has a DSB noise temperature of 1050 K at 2.5 THz.
|
|
|
|
Yagoubov, P. L., Hoogeveen, R. W. M., Maurellis, A. M., Mair, U., Krocka, M., Wagner, G., et al. (2003). TELIS — development of a new balloon borne THz/submm heterodyne limb sounder. In Proc. 14th Int. Symp. Space Terahertz Technol. (pp. 204–214).
Abstract: We present a design concept for a new state-of-the-art balloon borne atmospheric monitor that will allow enhanced limb sounding of the Earth's atmosphere within the submillimeter and far-infrared wavelength spectral range: TELIS, TErahertz and submm LImb Sounder. The instrument is being developed by a consortium of major European institutes that includes the Space Research Organisation of the Netherlands (SRON), the Rutherford Appleton Laboratory (RAL) in the United Kingdom and the Deutschen Zentrum far Luft- und Raumfahrt (DLR) in Germany (lead institute). TELIS will utilise state-of-the-art superconducting heterodyne technology and is designed to be a compact, lightweight instrument capable of providing broad spectral coverage, high spectral resolution and long flight duration (-24 hours duration during a single flight campaign). The combination of high sensitivity and extensive flight duration will allow evaluation of the diurnal variation of key atmospheric constituents such as OH, HO,, C10, BrO together will longer lived constituents such as 0 3 , HCL and N 2 0. Furthermore, TELIS will share a common balloon platform to that of the MIPAS-B Fourier Transform Spectrometer, developed by the Institute of Meteorology and Climate research of the University of Karlsruhe, Germany. MIPAS-B will provide simultaneous and complementary spectral measurements over an extended spectral range. The combination of the TELIS and MIPAS instruments will provide atmospheric scientists with a very powerful observational tool. TELIS will serve as a testbed for new cryogenic heterodyne detection techniques, and as such it will act as a prelude to future spacebome instruments planned by the European Space Agency (ESA).
|
|
|
|
Smirnov, K. V., Vachtomin, Y. B., Antipov, S. V., Maslennikov, S. N., Kaurova, N. S., Drakinsky, V. N., et al. (2003). Noise and gain performance of spiral antenna coupled HEB mixers at 0.7 THz and 2.5 THz. In Proc. 14th Int. Symp. Space Terahertz Technol. (pp. 405–412).
Abstract: Noise and gain performance of hot electron bolometer (HEB) mixers based on ultrathin superconducting NbN films integrated with a spiral antenna was studied. The noise temperature measurements for two samples with different active area of 3 p.m x 0.24 .tni and 1.3 1..tm x 0.12 1.tm were performed at frequencies 0.7 THz and 2.5 THz. The best receiver noise temperatures 370 K and 1600 K, respectively, have been found at these frequencies. The influence of contact resistance between the superconductor and the antenna terminals on the noise temperature of HEB is discussed. The noise and gain bandwidth of 5GHz and 4.2 GHz, respectively, are demonstrated for similar HEB mixer at 0.75 THz.
|
|
|
|
Il'in, K., Siegel, M., Semenov, A., Engel, A., Hübers, H. - W., Hollmann, E., et al. (2004). Thickness dependence of superconducting properties of ultrathin Nb and NbN films. In AKF-Frühjahrstagung.
|
|
|
|
Semenov, A., Richter, H., Hübers, H. - W., Smirnov, K., Voronov, B., & Gol'tsman, G. (2003). Development of terahertz superconducting hot-electron bolometer mixers. In Proc. 6th European Conf. Appl. Supercond. (Vol. 181, pp. 2960–2965).
Abstract: We present recent results of the development of phonon cooled hot-electron bolometric (HEB) mixers for airborne and balloon borne terahertz heterodyne receivers. Three iomportant issues have been addresses: the quality of NbN films the HEB mixers were made from, the spectral properties of the HEB mixers and the local oscillator power required for optical operation. Studies with an atomic force microscope indicate, that the performance of the HEB mixer might have been effected by the microstructure of the NbN film. Antenna gain and noise temperature were investigated at terahertz frequencies for a HEB embedded in either log-spiral or twin-slot feed antenna. Comparison suggests that at frequencies above 3 THz the spiral feed provides better overall performance. At 1.6 THz, a power of 2.5 µW was required from the local oscillator for optimal operation of the HEB mixer.
|
|
|
|
Richter, H., Semenov, A., Hubers, H. - W., Smirnov, K., Gol’tsman, G., & Voronov, B. (2004). Phonon cooled hot-electron bolometric mixer for 1-5 THz. In Proc. 29th IRMMW / 12th THz (pp. 241–242).
Abstract: Heterodyne receivers for applications in astronomy and planetary research need quantum limited sensitivity. In instruments which are currently built for SOFIA and Herschel, superconducting hot electron bolometers (HEB) are used to achieve this goal at frequencies above 1.4 THz. In order to optimize the performance for this frequency of 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/spl times/0.2 /spl mu/m/sup 2/ incorporated in a logarithmic spiral antenna. The DSB noise temperatures were 2700 K, 4700 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.
|
|
|
|
Zhang, J., Boiadjieva, N., Chulkova, G., Deslandes, H., Gol'tsman, G. N., Korneev, A., et al. (2003). Noninvasive CMOS circuit testing with NbN superconducting single-photon detectors. Electron. Lett., 39(14), 1086–1088.
Abstract: The 3.5 nm thick-film, meander-structured NbN superconducting single-photon detectors have been implemented in the CMOS circuit-testing system based on the detection of near-infrared photon emission from switching transistors and have significantly improved the performance of the system. Photon emissions from both p- and n-MOS transistors have been observed.
|
|
|
|
Gol’tsman, G. N., Smirnov, K., Kouminov, P., Voronov, B., Kaurova, N., Drakinsky, V., et al. (2003). Fabrication of nanostructured superconducting single-photon detectors. IEEE Trans. Appl. Supercond., 13(2), 192–195.
Abstract: Fabrication of NbN superconducting single-photon detectors, based on the hotspot effect is presented. The hotspot formation arises in an ultrathin and submicrometer-width superconductor stripe and, together with the supercurrent redistribution, leads to the resistive detector response upon absorption of a photon. The detector has a meander structure to maximally increase its active area and reach the highest detection efficiency. Main processing steps, leading to efficient devices, sensitive in 0.4-5 /spl mu/m wavelength range, are presented. The impact of various processing steps on the performance and operational parameters of our detectors is discussed.
|
|
|
|
Vakhtomin, Y. B., Finkel, M. I., Antipov, S. V., Smirnov, K. V., Kaurova, N. S., Drakinskii, V. N., et al. (2003). The gain bandwidth of mixers based on the electron heating effect in an ultrathin NbN film on a Si substrate with a buffer MgO layer. J. of communications technol. & electronics, 48(6), 671–675.
Abstract: Measurements of the intermediate frequency band 900 GHz of mixers based on the electron heating effect (EHE) in 2-nm- and 3.5-nm-thick superconducting NbN films sputtered on MgO and Si substrates with buffer MgO layers are presented. A 2-nm-thick superconducting NbN film with a critical temperature of 9.2 K has been obtained for the first time using a buffer MgO layer.
|
|
|
|
Semenov, A. D., Hübers, H. - W., Richter, H., Birk, M., Krocka, M., Mair, U., et al. (2002). 2.5 THz heterodyne receiver with NbN hot-electron-bolometer mixer. Phys. C: Supercond., 372-376, 448–453.
Abstract: We describe a 2.5 THz heterodyne receiver for applications in astronomy and atmospheric research. The receiver employs a superconducting NbN phonon-cooled hot-electron-bolometer mixer and an optically pumped far-infrared gas laser as local oscillator. 2200 K double sideband mixer noise temperature was measured at 2.5 THz across a 1 GHz intermediate frequency bandwidth centred at 1.5 GHz. The total conversion losses were 17 dB. The mixer response was linear at load temperatures smaller than 400 K. The receiver was tested in the laboratory environment by measuring the methanol line in emission. Observed pressure broadening confirms the true heterodyne detection regime of the mixer.
|
|
