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| Author | Swetz, D. S.; Bennett, D. A.; Irwin, K. D.; Schmidt, D. R.; Ullom, J. N. | ||||
| Title | Current distribution and transition width in superconducting transition-edge sensors | Type | Journal Article | ||
| Year | 2012 | Publication | Appl. Phys. Lett. | Abbreviated Journal  |
Appl. Phys. Lett. |
| Volume | 101 | Issue | Pages | 242603 | |
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| Abstract | Present models of the superconducting-to-normal transition in transition-edge sensors (TESs) do not describe the current distribution within a biased TES. This distribution is complicated by normal-metal features that are integral to TES design. We present a model with one free parameter that describes the evolution of the current distribution with bias. To probe the current distribution experimentally, we fabricated TES devices with different current return geometries. Devices where the current return geometry mirrors current flow within the device have sharper transitions, thus allowing for a direct test of the current-flow model.Measurements from these devices show that current meanders through a TES low in the resistivetransition but flows across the normal-metal features by 40% of the normal-state resistance. Comparison of transition sharpness between device designs reveals that self-induced magnetic fields play an important role in determining the width of the superconducting transition. | ||||
| Address | TES, current distribution | ||||
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| Notes | Recommended by Klapwijk | Approved | no | ||
| Call Number | Serial | 930 | |||
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| Author | Rasulova, G. K.; Brunkov, P. N.; Pentin, I. V.; Egorov, A. Y.; Knyazev, D. A.; Andrianov, A. V.; Zakhar’in, A. O.; Konnikov, S. G.; Gol’tsman, G. N. | ||||
| Title | A weakly coupled semiconductor superlattice as a potential for a radio frequency modulated terahertz light emitter | Type | Journal Article | ||
| Year | 2012 | Publication | Appl. Phys. Lett. | Abbreviated Journal |
Appl. Phys. Lett. |
| Volume | 100 | Issue | 13 | Pages | 131104 (1 to 4) |
| Keywords | semiconductor superlattice | ||||
| Abstract | The bolometer response to THz radiation from a weakly coupled GaAs/AlGaAs superlattice biased in the self-oscillations regime has been observed. The bolometer signal is modulated with the frequency equal to the fundamental frequency of superlattice self-oscillations. The frequency spectrum of the bolometer signal contains higher harmonics whose frequency is a multiple of fundamental frequency of self-oscillations. This work was supported by State Contracts Nos. 16.740.11.0044 and 16.552.11.7002 of Ministry of Education and Science of the Russian Federation. Structural characterization was made on the equipment of the Joint Research Centre «Material science and characterization in advanced technology» (Ioffe Institute, St. Petersburg, Russia). |
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| ISSN | 0003-6951 | ISBN | Medium | ||
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| Notes | Approved | no | |||
| Call Number | Serial | 1379 | |||
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| Author | Julia Toussaint, Roman Grüner, Marco Schubert, Torsten May, Hans-Georg Meyer, Benjamin Dietzek, Jürgen Popp, Matthias Hofherr, Matthias Arndt, Dagmar Henrich, Konstantin Il'in, and Michael Siegel | ||||
| Title | Superconducting single-photon counting system for optical experiments requiring time-resolution in the picosecond range | Type | Journal Article | ||
| Year | 2012 | Publication | Abbreviated Journal |
AIP REVIEW OF SCIENTIFIC INSTRUMENTS | |
| Volume | 83 | Issue | Pages | ||
| Keywords | SSPD, picosecond, time-resolution | ||||
| Abstract | We have developed a cryogenic measurement system for single-photon counting, which can be used in optical experiments requiring high time resolution in the picosecond range. The system utilizes niobium nitride superconducting nanowire single-photon detectors which are integrated in a timecorrelated single-photon counting (TCSPC) setup. In this work, we describe details of the mechanical design, the electrical setup, and the cryogenic optical components. The performance of the complete system in TCSPC mode is tentatively benchmarked using 140 fs long laser pulses at a repetition frequency of 75MHz. Due to the high temporal stability of these pulses, the measured time resolution of 35 ps (FWHM) is limited by the timing jitter of the measurement system. The result was crosschecked in a Coherent Anti-stokes Raman Scattering (CARS) setup, where scattered pulses from a β-barium borate crystal have been detected with the same time resolution. |
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| Notes | Approved | no | |||
| Call Number | RPLAB @ seleznev @ | Serial | 885 | ||
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| Author | Pütz, P.; Honingh, C. E.; Jacobs, K.; Justen, M.; Schultz, M.; Stutzki, J. | ||||
| Title | Terahertz hot electron bolometer waveguide mixers for GREAT | Type | Journal Article | ||
| Year | 2012 | Publication | Astron. Astrophys. | Abbreviated Journal |
A&A |
| Volume | 542 | Issue | Pages | L2 | |
| Keywords | HEB mixer, applications | ||||
| Abstract | Context. Supplementing the publications based on the first-light observations with the German REceiver for Astronomy at Terahertz frequencies (GREAT) on SOFIA, we present background information on the underlying heterodyne detector technology. This Letter complements the GREAT instrument Letter and focuses on the mixers itself. Aims. We describe the superconducting hot electron bolometer (HEB) detectors that are used as frequency mixers in the L1 (1400 GHz), L2 (1900 GHz), and M (2500 GHz) channels of GREAT. Measured performance of the detectors is presented and background information on their operation in GREAT is given. Methods. Our mixer units are waveguide-based and couple to free-space radiation via a feedhorn antenna. The HEB mixers are designed, fabricated, characterized, and flight-qualified in-house. We are able to use the full intermediate frequency bandwidth of the mixers using silicon-germanium multi-octave cryogenic low-noise amplifiers with very low input return loss. Results. Superconducting HEB mixers have proven to be practical and sensitive detectors for high-resolution THz frequency spectroscopy on SOFIA. We show that our niobium-titanium-nitride (NbTiN) material HEBs on silicon nitride (SiN) membrane substrates have an intermediate frequency (IF) noise roll-off frequency above 2.8 GHz, which does not limit the current receiver IF bandwidth. Our mixer technology development efforts culminate in the first successful operation of a waveguide-based HEB mixer at 2.5 THz and deployment for radioastronomy. A significant contribution to the success of GREAT is made by technological development, thorough characterization and performance optimization of the mixer and its IF interface for receiver operation on SOFIA. In particular, the development of an optimized mixer IF interface contributes to the low passband ripple and excellent stability, which GREAT demonstrated during its initial successful astronomical observation runs. |
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| Notes | Approved | no | |||
| Call Number | Serial | 907 | |||
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| Author | Shurakov, Alexander; Tong, Edward; Blundell, Raymond; Gol'tsman, Gregory | ||||
| Title | Microwave stabilization of HEB mixer by a microchip controller | Type | Conference Article | ||
| Year | 2012 | Publication | IEEE MTT-S international microwave symposium digest | Abbreviated Journal |
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| Volume | Issue | Pages | 1-3 | ||
| Keywords | HEB mixer stability, microwave injection, Allan variance, Allan time | ||||
| Abstract | The stability of a Hot Electron Bolometer (HEB) mixer can be improved by the use of microwave injection. In this article we report a refinement of this approach. We introduce a microchip controller to facilitate the implementation of the stabilization scheme, and demonstrate that the feedback loop effectively suppresses drifts in the HEB bias current, leading to an improvement in the receiver stability. The measured Allan time of the mixer's IF output power is increased to > 10 s. | ||||
| Address | Montreal, QC, Canada | ||||
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| Notes | Approved | no | |||
| Call Number | Serial | 857 | |||
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