| Records |
| Author |
Korneev, A.; Kouminov, P.; Matvienko, V.; Chulkova, G.; Smirnov, K.; Voronov, B.; Gol'tsman, G. N.; Currie, M.; Lo, W.; Wilsher, K.; Zhang, J.; Słysz, W.; Pearlman, A.; Verevkin, A.; Sobolewski, Roman |
| Title |
Sensitivity and gigahertz counting performance of NbN superconducting single-photon detectors |
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Journal Article |
| Year |
2004 |
Publication |
Appl. Phys. Lett. |
Abbreviated Journal |
Appl. Phys. Lett. |
| Volume |
84 |
Issue |
26 |
Pages |
5338-5340 |
| Keywords |
SSPD, NEP, QE |
| Abstract |
We have measured the quantum efficiencysQEd, GHz counting rate, jitter, and noise-equivalentpowersNEPdof nanostructured NbN superconducting single-photon detectorssSSPDsdin thevisible to infrared radiation range. Our 3.5-nm-thick and 100- to 200-nm-wide meander-typedevices(total area 10310mm2), operating at 4.2 K, exhibit an experimental QE of up to 20% inthe visible range and,10% at 1.3 to 1.55mm wavelength and are potentially sensitive up tomidinfrareds,10mmdradiation. The SSPD counting rate was measured to be above 2 GHz withjitter,18 ps, independent of the wavelength. The devices’ NEP varies from,10−17W/Hz1/2for1.55mm photons to,10−20W/Hz1/2for visible radiation. Lowering the SSPD operatingtemperature to 2.3 K significantly enhanced its performance, by increasing the QE to,20% andlowering the NEP level to,3310−22W/Hz1/2, both measured at 1.26mm wavelength. |
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0003-6951 |
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532 |
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Siddiqi, I.; Prober, D. E. |
| Title |
Nb–Au bilayer hot-electron bolometers for low-noise THz heterodyne detection |
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Journal Article |
| Year |
2004 |
Publication |
Applied Physics Letters |
Abbreviated Journal |
Appl. Phys. Lett. |
| Volume |
84 |
Issue |
8 |
Pages |
1404 |
| Keywords |
HEB, mixers, dynamic range, saturation, LO power, local oscillator power, Nb |
| Abstract |
The sensitivity of present Nb diffusion-cooled hot-electron bolometer (HEB) mixers is not quantum limited, and can be improved by reducing the superconducting transition temperature TC. Lowering TC reduces thermal fluctuations, resulting in a decrease of the mixer noise temperature TM. However, lower TC mixers have reduced dynamic range and saturate more easily due to background noise. We present 30 GHz microwave measurements on a bilayer HEB system, Nb–Au, in which TC can be tuned with Au layer thickness to obtain the maximum sensitivity for a given noise background. These measurements are intended as a guide for the optimization of THz mixers. Using a Nb–Au mixer with TC = 1.6 K, we obtain TM = 50 K with 2 nW of local oscillator (LO) power. Good mixer performance is observed over a wide range of LO power and bias voltage and such a device should not exhibit saturation in a THz receiver. |
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0003-6951 |
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571 |
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van't Klooster, K.; Myasnikova, S. E.; Parshin, V. V.; Kasparek, W. |
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Results of reflection loss measurements of sample material for radio astronomy telescope antenna for Planck Project |
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Conference Article |
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2004 |
Publication |
Proc. 14th international crimean conference on microwave and telecommunication technology |
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753-755 |
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mirror, reflection index, emissivity, Fabry-Perot interferometer, space observatory, terahertz, THz |
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Advanced radio telescope antennas for space applications are realised by the use of stable composite materials, which are lighter in general than various metal realisations. Reflectivity measurements have been carried out on high technology samples for the Planck radio telescope. Highly accurate results have been obtained at the Applied Physics Institute in Nizhny Novgorod, and an independent measurement with a totally different setup at the University of Stuttgart confirmed that one of the samples showed a strange behaviour. Moreover, it confirmed the high accuracy of the testing method. |
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579 |
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González, Francisco Javier; Alda, Javier; Ilic, Bojan; Boreman, Glenn D. |
| Title |
Infrared Antennas Coupled to Lithographic Fresnel Zone Plate Lenses |
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Journal Article |
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2004 |
Publication |
Applied Optics |
Abbreviated Journal |
Appl. Opt. |
| Volume |
43 |
Issue |
33 |
Pages |
6067-6073 |
| Keywords |
optical antennas |
| Abstract |
Several designs for Fresnel zone plate lenses (FZPLs) to be used in conjunction with antenna-coupled infrared detectors have been fabricated and tested. The designs comprise square and circular FZPLs with different numbers of Fresnel zones working in transmissive or reflective modes designed to focus infrared energy on a square-spiral antenna connected to a microbolometer. A 163× maximum increase in response was obtained from a 15-zone circular FZPL in the transmissive mode. Sensor measurements of normalized detectivity D* resulted in a 2.67× increase with FZPLs compared with measurements made of square-spiral antennas without FZPLs. The experimental results are discussed and compared with values obtained from theoretical calculations. |
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RPLAB @ gujma @ |
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740 |
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Kramer, B.; Chen, C-C.; Volakis, J.D. |
| Title |
The development of a mini-UWB antenna |
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Journal Article |
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2004 |
Publication |
Measurement and Techniques Association Symposium |
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AMTA |
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6 |
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optical antennas; Ultra Wide Band; Spiral Antenna, Dielectric Loading |
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There is a great interest in the automotive and military sectors for small and broadband antennas that meet modern communication needs. These needs require ultra-wide bandwidth (>10:1) UWB antennas, such as the spiral antenna. However, the physical size at the low-frequency end typically becomes too large for practical applications. To reduce the size of the antenna, miniaturization techniques must be employed such as the use of high-contrast dielectric materials. Size reduction using high-contrast materials has been demonstrated for narrowband antennas, such as patch antennas, but not for broadband antennas to our knowledge. Therefore, the concept of miniaturizing a broadband spiral antenna using dielectric materials will be investigated experimentally and numerically.Issues that arise from dielectric loading such as impedance reduction will also be addressed. It will be shown using the results from these studies that there are practical limitations to the amount of miniaturization which can be achieved. |
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RPLAB @ gujma @ |
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751 |
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