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| 3. |
- Cherednichenko, Serguei, 1970, et al.
(författare)
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Hot-electron bolometer terahertz mixers for the Herschel Space Observatory
- 2008
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 79:034501, s. 034501-1 to 034501-10-
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Tidskriftsartikel (refereegranskat)abstract
- We report on low noise terahertz mixers (1.4–1.9 THz) developed for the heterodyne spectrometer onboard the Herschel Space Observatory. The mixers employ double slot antenna integrated superconducting hot-electron bolometers (HEBs) made of thin NbN films. The mixer performancewas characterized in terms of detection sensitivity across the entire rf band by using a Fourier transform spectrometer (from 0.5 to 2.5 THz, with 30 GHz resolution) and also by measuring the mixer noise temperature at a limited number of discrete frequencies. The lowest mixer noise temperature recorded was 750 K (double sideband (DSB)) at 1.6 THz and 950 K DSB at 1.9 THz local oscillator (LO) frequencies. Averaged across the intermediate frequency band of 2.4–4.8 GHz,the mixer noise temperature was 1100 K DSB at 1.6 THz and 1450 K DSB at 1.9 THz LO frequencies. The HEB heterodyne receiver stability has been analyzed and compared to the HEBstability in the direct detection mode. The optimal local oscillator power was determined and found to be in a 200–500 nW range.
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| 4. |
- Khosropanah, Pourya, 1971, et al.
(författare)
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Aging Investigation of NbN Hot Electron Bolometer Mixer
- 2005
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Ingår i: Proceedings of 16th International Symposium on Space THz Technology, Gothenburg, Sweden, May. 2005.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work presents the aging investigation of NbNHEB mixers in usual lab conditions and also in high temperatureand high relative humidity environment. A variety of devices havebeen fabricated using different combinations of resist (SAL), Si,SiO2 and SiN single and multi-layer for bolometer protection.In the accelerated aging tests the degradation is monitored bymeasuring the DC resistance of the devices during the test. Theresults show that using multi-layer protection increase the devicelifetime significantly.
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| 5. |
- Khosropanah, Pourya, 1971, et al.
(författare)
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Analysis of NbN Hot Electron Bolometer Receiver Noise Temperatures Above 2 THz With a Quantum Noise Model
- 2009
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Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 19:3, s. 274-277
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Tidskriftsartikel (refereegranskat)abstract
- This paper summarizes our receiver noise temperature data of NbN HEB mixers obtained at a number of local oscillator frequencies between 1.9 to 4.3 THz in order to verify the role of quantum noise. The experimental data show that the receiver noise temperature increases roughly linearly with frequency. At 4.3 THz, we measured a receiver noise temperature of 1300 K, which is about 6 times (hf/k B) . The noise data at different frequencies are compared to a prediction of a noise model including the contribution of quantum noise and making use of a hot-spot model for mixing. We draw a preliminary conclusion that at 4.3 THz roughly 30% of the receiver noise temperature can be ascribed to the quantum noise. However, more dedicated measurements are required in order to further support the quantum noise model for HEB mixers.
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- Khosropanah, Pourya, 1971
(författare)
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NbN and NbTiN Hot Electron Bolometer THz Mixers
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis reports the development of Hot Electron Bolometer (HEB) mixers for radio astronomy heterodyne receivers in THz frequency range. Part of this work is the fabrication of HEB devices, which are based on NbN or NbTiN superconducting thin films (≤5 nm). They are integrated with wideband spiral or double-slot planar antennas. The mixer chips are incorporated into a quasi-optical receiver. The experimental part of this work focuses on the characterization of the receiver as a whole, and the HEB mixers as a part. Double side band receiver noise temperature and the IF bandwidth are reported for frequencies from 0.7 THz up to 2.6 THz. The spectrum of the direct response of HEB integrated with dierent antennas are measured using Fourier Transform Spectrometer (FTS). The effect of the bolometer size on total receiver performance and the LO power requirements is also discussed. A high-yield and reliable process for fabrication of NbN HEB mixers have been achieved. Over 100 devices with different bolometer geometry, film property and also different antennas have been fabricated and measured. The measured data enables us to discuss the impact of different parameters to the receiver overall performance. This work has provided NbN HEB mixers to the following receivers: TREND (Terahertz REceiver with NbN HEB Device) operating at 1.25-1.5 THz, installed in AST/RO Submillimeter Wave Telescope, Amundsen/Scott South Pole Station, in 2002-2003. Band 6-low (1.410-1.700 THz) and 6-high (1.700-1.920 THz) of the HIFI (Heterodyne Instrument for Far Infra-red) in the Herschel Space Observatory, due to launch in 2007 by ESA (European Space Agency). Besides, there has been continuous efforts to develop better models to explain the mixer performance more accurately. They are based on two temperature model for electrons and phonons and solving one-dimensional heat balance equations along the bolometer. The principles of these models are illustrated and the calculated results are compared with measured data.
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| 7. |
- Kollberg, Erik, 1937, et al.
(författare)
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Impedance of Hot-Electron Bolometer Mixers at Terahertz Frequencies
- 2011
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 1:2, s. 383-389
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Tidskriftsartikel (refereegranskat)abstract
- This paper discusses the current distribution in thin-film devices, especially in a hot-electron bolometer (HEB) mixer at terahertz frequencies, and the consequences of different current distributions on the device impedance. We first present an approximate analytical model from which we derive a proposed rule of thumb for deciding when the film is thin enough to support a current distribution that is uniform in the transverse direction. We then verify this rule by performing electromagnetic simulations. Our conclusion is that the current distribution in thin films with a relatively high DC resistivity and small film thickness with respect to the skin depth is essentially uniform up to 8 THz. These results are crucial, e.g., for understanding radiation coupling between an HEB and an antenna and indispensable when analyzing detectors and receivers based on bolometric properties of thin films.
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| 8. |
- Kollberg, Erik, 1937, et al.
(författare)
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Quantum noise contribution to NbN hot electron bolometer receiver
- 2009
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Ingår i: Proceedings of the 20th International Symposium on Space Terahertz Technology, Charlottesville, 20-22 April 2009. ; , s. 155-
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Konferensbidrag (refereegranskat)abstract
- Abstract— Superconducting NbN hot electron bolometer (HEB) mixers are so far the most sensitive detectors forheterodyne spectroscopy in the frequency range between 1.5 THz and 5 THz. To reach the ultimate receiver noisetemperatures in the high end of the THz range (3-6 THz), it is crucial to understand their fundamental noise contributionfrom different origins. With increasing frequency, the classical output noise contribution should remain unchanged, butthe quantum noise contribution is expected to play an increasing role [1].This paper reports the first dedicated experiment using a single NbN HEB mixer at a number of local oscillatorfrequencies between 1.6 to 4.3 THz to address and quantify the contribution of the quantum noise to the receiver noisetemperature.We used a spiral antenna coupled NbN HEB mixer with a bolometer size of 2 μm×0.2 μm. In order to minimizeuncertainties in the corrections of the optical losses, we use a vacuum hot/cold load setup [2] to eliminate the air loss, andan uncoated elliptical Si lens. Although other components, a 3 μm Mylar beam splitter and a QMC heat filter, alsointroduce frequency dependent optical losses, they can be accurately calibrated. Furthermore, to reduce uncertainties inthe data, we measure Y-factors responding to the hot/cold load by fixing the voltage, but varying the LO power [2]. AsLO, we use a FIR gas laser.We measure the Y-factor at the optimal point at different frequencies by only varying LO frequencies, but keepingthe rest exactly the same. We obtain DSB receiver noise temperatures, which are 842 K (at 1.6 THz), 845 K (1.9 THz), 974K (2.5 THz) and 1372 K (4.3 THz). After the correction for the losses of the QMC filter and the beam splitter, the noisedata show a linear increase with increasing frequency.Using a quantum noise model [1] for HEB mixers and using a criterion for which the classical output noise must beconstant at different frequencies, we analyze the results and find the excess quantum noise factor β to be around 2 andthat 24 % of the total receiver noise temperature at 4.3 THz (at the input of the entire receiver) can be ascribed toquantum noise. Clearly the quantum noise has a small but measurable effect on the receiver noise temperature at thisfrequency.We are still analyzing different alternatives of interpretation for the mismatch loss between the bolometer andthe spiral antenna.[1] E. L. Kollberg and K. S. Yngvesson, “Quantum-noise theory for terahertz hot electron bolometer mixers,” IEEE Trans.Microwave Theory and Techniques, 54, 2077, 2006.[2] P. Khosropanah, J.R. Gao, W.M. Laauwen, M. Hajenius and T.M. Klapwijk, “Low noise NbN hot-electron bolometer mixerat 4.3 THz,” Appl. Phys. Lett., 91, 221111, 2007.
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| 9. |
- Wild, W., et al.
(författare)
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Millimetron—a large Russian-European submillimeter space observatory
- 2009
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Ingår i: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 23:1, s. 221-244
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Tidskriftsartikel (refereegranskat)abstract
- Millimetron is a Russian-led 12 m diameter submillimeter and far-infrared space observatory which is included in the Space Plan of the Russian Federation for launch around 2017. With its large collecting area and state-of-the-art receivers, it will enable unique science and allow at least one order of magnitude improvement with respect to the Herschel Space Observatory. Millimetron will be operated in two basic observing modes: as a single-dish observatory, and as an element of a ground-space very long baseline interferometry (VLBI) system. As single-dish, angular resolutions on the order of 3 to 12 arc sec will be achieved and spectral resolutions of up to a million employing heterodyne techniques. As VLBI antenna, the chosen elliptical orbit will provide extremely large VLBI baselines (beyond 300,000 km) resulting in micro-arc second angular resolution.
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| 10. |
- Zhang, W., et al.
(författare)
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Quantum noise in a terahertz hot electron bolometer mixer
- 2010
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 96:11, s. 111113 -
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the noise temperature of a single, sensitive superconducting NbN hot electron bolometer (HEB) mixer in a frequency range from 1.6 to 5.3 THz, using a setup with all the key components in vacuum. By analyzing the measured receiver noise temperature using a quantum noise (QN) model for HEB mixers, we confirm the effect of QN. The QN is found to be responsible for about half of the receiver noise at the highest frequency in our measurements. The beta-factor (the quantum efficiency of the HEB) obtained experimentally agrees reasonably well with the calculated value.
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