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Sökning: WFRF:(Bevilacqua Stella 1981)

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1.
  • Bevilacqua, Stella, 1981, et al. (författare)
  • Characterisation and Modeling of MgB2 HEBs IF impedance
  • 2016
  • Ingår i: Swedish Microwave Days March 15-16, 2016, Linköping, Sweden. ; , s. 55-
  • Konferensbidrag (refereegranskat)abstract
    • Here we present the method which allows to measure quiteaccurately the HEB impedance employing just one cooling.By knowing the HEB IF impedance a coupling matchingnetwork can be designed for a possible packaged receiver.
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2.
  • Bevilacqua, Stella, 1981, et al. (författare)
  • Fast room temperature THz bolometers
  • 2013
  • Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - 2162-2027 .- 2162-2035. - 9781467347174 ; , s. 1-2
  • Konferensbidrag (refereegranskat)abstract
    • A responsivity of >100 V/W was measured at roomtemperature for nano scale bolometers integrated with planar spiral antennas covering a frequency range from 100 GHz to 3 THz. Currently a NEP of about 200 pW/Hz^0.5 was experimentally obtained.
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3.
  • Bevilacqua, Stella, 1981, et al. (författare)
  • Fast room temperature THz microbolometers
  • 2012
  • Ingår i: 23rd International Symposium on Space Terahertz Technology.
  • Konferensbidrag (refereegranskat)abstract
    • We will present experimental and theoretical investigation of room temperature high speed THz detectors based on thin YBa2Cu3O7 films. These films have TCR of 0.35%/K, and can sustain large bias current densities. With a resistivity of 100-200 µOhm×cm for a film thickness of 50nm, it is very straightforward to impedance match such bolometers with planar antennas. The responsivity is a function of the bolometer planar dimensions and the films thickness. The currently achieved responsivity is 30 V/W and Johnson noise limited NEP is 70pW/Hz^0.5. The bolometer bandwidth is limited by the antenna bandwidth and spans from microwaves to over a few THz. Experimenatl investigation is done from 100GHz to 2.5THz. The measured response time is 2ns. We will also present results of the bolometer performance as their dimensions reduce to sub-µm.
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4.
  • Bevilacqua, Stella, 1981, et al. (författare)
  • HEB mixers for THz radio astronomy
  • 2014
  • Ingår i: Swedish Microwave Days March 11-12, 2014.
  • Konferensbidrag (refereegranskat)abstract
    • Hot-Electron Bolometer (HEB) mixers made of 10 nm superconducting MgB2 films are discussed for high sensitivity high spectral resolution spectrometers for radio astronomy. The key advantage of the used MgB2 films is in achievement of wider Intermediate Frequency (IF) bandwidth.
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5.
  • Bevilacqua, Stella, 1981, et al. (författare)
  • High Sensitivity Terahertz Bolometers as Room Temperature Detectors
  • 2014
  • Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - 2162-2027 .- 2162-2035. - 9781479938773 ; , s. Art. no. 6956197-
  • Konferensbidrag (refereegranskat)abstract
    • High sensitivity room temperature THz direct detectors made of YBa2Cu3O7-x nano-bridges, with a broadband optical coupling (0.1-2THz) are presented. An optical responsivity (RV) up to 45 V/W was measured at 400 GHz. For bolometers with an electrical responsivity of 70 V/W a noise equivalent power (NEP) of 50 pW/Hz0.5 was experimental obtained.
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6.
  • Bevilacqua, Stella, 1981, et al. (författare)
  • Investigation of MgB2 HEB mixer gain bandwidth
  • 2011
  • Ingår i: International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz), 2011. - 2162-2027. - 9781457705083 ; , s. 1 - 2
  • Konferensbidrag (refereegranskat)abstract
    • THz mixers based on superconducting MgB2 bolometers were fabricated by photolithography and Ar-ion beam milling on sapphire substrates. The mixer gain bandwidth of 3.4 GHz, 2.3 GHz and 1.3 GHz were measured for 10, 15 and 30 nm films respectively.
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7.
  • Bevilacqua, Stella, 1981, et al. (författare)
  • Low noise MgB2 terahertz hot-electron bolometer mixers
  • 2012
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:3
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on low noise terahertz bolometric mixers made of MgB2 superconducting thin films. For a 10-nm-thick MgB2 film, the lowest mixer noise temperature was 600 K at 600 GHz. For 30 to 10-nm-thick films, the mixer gain bandwidth is an inverse function of the film thickness, reaching 3.4 GHz for the 10-nm film. As the critical temperature of the film decreases, the gain bandwidth also decreases, indicating the importance of high quality thin films for large gain bandwidth mixers. The results indicate the prospect of achieving a mixer gain bandwidth as large as 10-8 GHz for 3 to 5-nm-thick MgB2 films.
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8.
  • Bevilacqua, Stella, 1981, et al. (författare)
  • Low Noise Nanometer Scale Room-Temperature YBa2Cu3O7-x Bolometers for THz Direct Detection
  • 2014
  • Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 4:6, s. 653- 660
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a detailed investigation of the responsivity and the noise in room temperature THz direct detectors made of YBa2Cu3O7-x (YBCO) thin film nano bolometers. The YBCO nano bolometers are integrated with planar spiral antennas covering a frequency range from 100 GHz to 2 THz. The detectors were characterized at 1.6 THz, 0.7 THz, 400 GHz and 100 GHz. The maximum electrical responsivity of 70 V/W and a minimum noise equivalent power (NEP) of 50 pW/Hz0.5 were measured, whereas the highest optical responsivity was 45 V/W. The 1/f noise in nano bolometers is independent on the device volume and can be found as (VN/V)2=6×10-11×1/f Hz-1 for a given modulation frequency f and a dc voltage V.
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9.
  • Bevilacqua, Stella, 1981, et al. (författare)
  • MgB2 Hot-Electron Bolometer Mixers at Terahertz Frequencies
  • 2015
  • Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 25:3, s. 2301104-
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we compare the performance of MgB2 Hot-Electron Bolometer Mixers operating at Local Oscillator frequencies of 0.6 and 1.63 THz. The minimum noise temperatures that were obtained are 700 and 1150 K for 0.6 and 1.63 THz, respectively. The receiver noise bandwidth is of the order of 2.2-3 GHz for 10-nm-thick HEB devices with a Tc of 8.5 K. Sub-micrometer size HEBs were also fabricated with no degradation of the initial film quality when a 20-nm MgB2 film with a Tc of 22 K was used. In the direct detection mode, the maximum voltage responsivity is in the range of 1-2 kV/W at 1.63 THz and the optimal bias current is around 1/4-1/3 of the Ic at 4.2 K.
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10.
  • Bevilacqua, Stella, 1981, et al. (författare)
  • MgB2 Hot Electron Bolometers for THz radio astronomy
  • 2012
  • Ingår i: 23rd International Symposium on Space Terahertz Technology.
  • Konferensbidrag (refereegranskat)abstract
    • We discuss Hot Electron Bolometer (HEB) THz mixers made of superconducting Magnesium Diboride (MgB2) films. The films of 30 nm, 15 nm and 10 nm thick were deposited on sapphire substrates. The MgB2 HEBs were patterned as a bridge at the feed point of a spiral antenna. The performance of the devices was investigated with respect to the gain bandwidth (GBW) and the noise temperature. The GBW was measured via mixing two signal sources (BWOs at 600 GHz). For the given films thicknesses, the GBW was measured to be 1.3 GHz, 2.3 GHz and 3.4 GHz, which is larger than for the NbN HEB mixers made of the same films thicknesses. Using the Y-factor technique a noise temperature of 800 K at 600 GHz local oscillator (LO) frequency was measured for mixers made of 10 nm MgB2 film. Besides the films thickness, the gain and the noise bandwidths are functions of the films critical temperature, Tc. For 10nm films, with Tc=15K, a noise bandwidth on the order of 8GHz was measured. From these measurements and from the material parameters a GBWof 8 GHz (noise bandwidth >10GHz) is expected for 3-5 nm MgB2 films.
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11.
  • Bevilacqua, Stella, 1981, et al. (författare)
  • Room Temperature THz Detectors with Fast Response Rate.
  • 2014
  • Ingår i: Swedish Microwave Days March 11-12, 2014, Gothenburg, Sweden.
  • Konferensbidrag (refereegranskat)abstract
    • We present high sensitivity room temperature THz direct detectors made of YBa2Cu3O7-x nano-bridges, with a broadband optical coupling (0.1-2THz). A responsivity (Rv) up to 100 V/W and a noise equivalent power (NEP) of 200 pW/Hz0.5 were measured for a device area of 0.15 μm2 -0.25 μm2.
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12.
  • Bevilacqua, Stella, 1981, et al. (författare)
  • Study of IF bandwidth of MgB2 phonon-cooled hot-electron bolometer mixers
  • 2013
  • Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 3:4, s. 409-415
  • Tidskriftsartikel (refereegranskat)abstract
    • A noise bandwidth (NBW) of 6-7 GHz was obtained for Hot-Electron Bolometer (HEB) mixers made of 10 nm MgB2 films. A systematic investigation of the (IF) gain bandwidth as a function of the MgB2 film thickness (30 nm, 15 nm and 10 nm) is also presented. The gain bandwidth (GBW) of 3.4 GHz was measured for a 10 nm film, corresponding to a mixer time constant of 47 ps. For 10 nm films a reduction of the GBW was observed with the reduction of the critical temperature (Tc). Experimental data were analyzed using the two-temperature model. From the theoretical analysis, the electron-phonon time (τe-ph), the phonon escape time (τesc) and the electron and phonon specific heats (ce, cph) were extrapolated giving the first model for HEB mixers of MgB2 films.
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13.
  • Bevilacqua, Stella, 1981 (författare)
  • Study of MgB2 and YBa2Cu3O7-x Microbolometers for THz Sensing Applications
  • 2014
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In this thesis, two novel THz detectors based on magnesium diboride (MgB2)and yttrium barium copper oxide (YBa2Cu3O7-x) are presented. In particular,MgB2 superconductor is used for the investigation of hot-electron bolometer(HEB) mixers, while YBa2Cu3O7-x is explored in microbolometers for room-temperaturecoherent and incoherent detection.Superconducting NbN hot electron bolometer (HEB) mixers are widelyused in terahertz radio astronomy. HEB mixers are the most sensitive mixersat frequency above 1THz. However, their drawback is a limited IF bandwidth.Due to the short electron-phonon interaction time, MgB2 is a promisingsuperconductor for an improved gain bandwidth in HEB mixers.MgB2 HEBs integrated with spiral antenna were fabricated, characterisedand studied. The gain bandwidth was investigated with respect to the thicknessand the critical temperature of the film. A gain bandwidth of 1.3GHz, 2.3GHzand 3.4GHz was measured in 30 nm, 15 nm and 10 nm MgB2 films, respectively.Using the two temperature model the experimental gain bandwidths data wereanalysed and, the electron-phonon interaction time, τe−ph of 7 ps to 15 ps, thephonon escape time, τesc of 4.8 ps to 42 ps were extracted resulting on the firstmodel for HEB mixers made of MgB2 films. At 600GHz and 1.6THz, the lowestnoise temperature was measured to be 800K and 1150K at a bath temperatureof 4.2K, respectively. A noise bandwidth as large as 6-7GHz was measured forHEB mixers fabricated from 10 nm films with a critical temperature of 15K.YBa2Cu3O7-x microbolometers on bulk substrate integrated with planarantennas were investigated at room-temperature. The highest electrical andoptical responsivity was measured to be 230V/W and 45V/W at 1mA biascurrent while the minimum noise equivalent power was 50 pW/Hz0.5. A largevariety of bolometers with different areas, geometries, resistances and volumeswere studied showing that the noise voltage normalised to the voltage drop overthe bolometers was constant and equal to (VN/V)2=6×10−11×1/f×Hz−1. It isexpected that this value can be used as a rule of thumb for the noise estimationof any YBa2Cu3O7-x bolometers in the limit of 1/f noise. Heterodyne mixermeasurements of YBa2Cu3O7-x bolometers showed a response time of 2.5 nswhich is the lowest reported among room-temperature bolometers.
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14.
  • Bevilacqua, Stella, 1981, et al. (författare)
  • Submicrometer MgB2 hot electron bolometer mixers
  • 2013
  • Ingår i: The 24th International Symposium on Space Terahertz Technology.
  • Konferensbidrag (refereegranskat)abstract
    • Phonon-cooled hot electron bolometer mixers based on MgB2 film are promising candidates for THz radio astronomy at frequency above 1 THz. The short electron-phonon interaction time and the high critical temperature of the MgB2 (39 K in the bulk), compared to other intermetallic compounds, make it suitable for applications where wide IF bandwidth and low noise are needed. The currently achieved gain and noise bandwidths are 3.4 GHz and 7 GHz for HEBs fabricated in 10 nm MgB2 films. The noise temperature of 800 K was measured at 600 GHz local oscillator (LO) frequency using the Y-factor technique.MgB2 has been demonstrated to be sensitive to the oxygen as well as water, therefore it makes the fabrication of sub-µm HEBs very challenging. HEBs were fabricated using electron beam lithography in 10 nm MgB2 films with a bolometer area in the range of 0.09 and 0.25 µm2. We report the performance of the devices respect to the noise temperature at LO frequency up to 2.5 THz. Using the isothermal technique the LO power requirement was estimated respect to the bolometer area. Based on the material parameters obtained from the experiments, the two temperature model simulations showed a gain bandwidth as large as 8-10 GHz for thin MgB2 films.
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15.
  • Bevilacqua, Stella, 1981 (författare)
  • Superconducting THz mixers based on MgB2 film
  • 2013
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Superconducting NbN hot electron bolometer (HEB) mixers are widely used in terahertz radio astronomy. Such mixers have superior performance compared to SIS and Schottky diode mixers at frequency above 1THz. However, their drawback is a limited IF bandwidth. Therefore, as radio astronomy advances towards higher frequencies, mixers with even wider gain bandwidth are required. The gain bandwidth of the HEB mixers is determined by two consequent processes in the electron energy relaxation: the electron phonon interaction and the phonon escape into the substrate with corresponding time constants for each process. The electron-phonon interaction time is inversely dependent of the electron temperature of the film which is close to the critical temperature of the superconductor. The escape time is dependent of the film thickness. Materials with higher critical temperature and shorter electron relaxation time are needed to improve the IF bandwidth. The discovery of the superconductivity in the intermetallic compound magnesium diboride (MgB2) has generated a great interest in this research field. The high critical temperature and the short electron phonon interaction time make the MgB2 very attractive for HEB mixers fabrication aiming for better HEB mixers performances. In this thesis, novel terahertz HEB mixers based on magnesium diboride thin films are presented. MgB2 HEBs integrated with spiral antenna were fabricated, characterized and studied. The gain bandwidth was investigated with respect to the thickness and the critical temperature of the film. A gain bandwidth of 1.3GHz, 2.3GHz and 3.4GHz corresponding to a mixer time constant of 130 ps, 70 ps and 47 ps was measured in 30 nm, 15 nm and 10 nm MgB2 films, respectively. Another important figure of merit for receivers is the noise temperature which is influenced by several factors such as the dimension of the HEB and the critical current. For HEB mixers made from 10 nm MgB2 film the lowest mixer noise temperature was 600K measured at 2K bath temperature and 600GHz local oscillator (LO) frequency. Finally, using the two temperature model the experimental data were analyzed and the electron phonon interaction time, τe-ph of 7 to 15 ps, the phonon escape time, τesc of 6 to 42 ps and the specific heat ratio, ce/cph of 1.35 to 9 ps were extracting giving the first model for HEB mixers made of MgB2 films. Based on this research a gain bandwidth as large as 8-10GHz has been predicted in very thin MgB2 films.
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16.
  • Bevilacqua, Stella, 1981, et al. (författare)
  • Wideband MgB2 Hot-Electron Bolometer Mixers: IF Impedance Characterisation and Modeling
  • 2016
  • Ingår i: IEEE Transactions on Applied Superconductivity. - 1558-2515 .- 1051-8223. ; 26:3, s. 2300105-
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper we present a method for low signal S11 parameter vector measurements of a cryogenic device in the microwave frequency range. In particular, the intermediate frequency (IF) impedance of MgB2 Hot-electron Bolometer (HEB) mixers was investigated over a frequency range of 100 MHz to 10 GHz. A new cryogenic calibration technique, which employs the HEB as a calibration kitandrequires two consecutive thermal cycles, was developed for this purpose.The real part of measured IF impedance showed a strong correlationwith the differential resistance (dV/dI) obtained from the dc I-V curves while the imaginary partwas capacitive for almost the entire frequency range.
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17.
  • Bevilacqua, Stella, 1981, et al. (författare)
  • YBCO Terahertz Detectors at Room Temperature and at 77K.
  • 2014
  • Ingår i: 12th HTSHFF Workshop High Temperature Superconductors in High Frequency Fields, June 9-12, 2014, Fréjus, France.
  • Konferensbidrag (refereegranskat)abstract
    • The diversity of THz detectors is as wide as the range of applications for THz waves. Requirements for the detectors vary and so do the detectors. Extremely high sensitivities (NEP 200V/W) for frequencies from 100GHz to 2THz and a drop of NEP to about 70 pW/Hz0.5. As the responsivity grows, the nano bolometers become more sensitive to the external electrical disturbances, as well as to the internal 1/f noise. We will discuss the noise properties of the YBCO nano bolometers, their optical characterization, as well as some of their application for the gas spectroscopy and prospects of the array integration.
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18.
  • Cha, Eunjung, 1985, et al. (författare)
  • Two-Finger InP HEMT Design for Stable Cryogenic Operation of Ultra-Low-Noise Ka- and Q-Band LNAs
  • 2017
  • Ingår i: IEEE Transactions on Microwave Theory and Techniques. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9480 .- 1557-9670. ; 65:12, s. 5171-5180
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate the cryogenic stability of two-finger 100-nm gate-length InP HEMTs aimed for Ka- and Q-band ultra-low noise amplifiers (LNAs). InP HEMTs with unit gate widths ranging between 30 and 50 mu m exhibit unstable cryogenic behavior with jumps in drain current and discontinuous peaks in transconductance. We also find that shorter gate length enhances the cryogenic instability. We demonstrate that the instability of two-finger transistors can be suppressed by either adding a source air bridge, connecting the back end of gates, or increasing the gate resistance. A three-stage 24-40 GHz and a four-stage 28-52-GHz monolithic microwave-integrated circuit LNA using the stabilized InP HEMTs are presented. The Ka-band amplifier achieves a minimum noise temperature of 7 K at 25.6 GHz with an average noise temperature of 10.6 K at an ambient temperature of 5.5 K. The amplifier gain is 29 dB +/- 0.6 dB. The Q-band amplifier exhibits minimum noise temperature of 6.7 K at 32.8 GHz with average noise temperature of 10 K at ambient temperature of 5.5 K. The amplifier gain is 34 dB +/- 0.8 dB. To our knowledge, the Ka- and Q-band amplifiers demonstrate the lowest noise temperature reported so far for InP cryogenic LNAs.
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19.
  • Cha, Eunjung, 1985, et al. (författare)
  • Two-finger InP HEMT design for stable cryogenic operation of ultra-low-noise Ka-band LNAs
  • 2017
  • Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 9781509063604 ; , s. 168-171
  • Konferensbidrag (refereegranskat)abstract
    • We have investigated the cryogenic stability of two-finger InP HEMTs aimed for Ka-band ultra-low noise amplifiers (LNAs). Unlike two-finger transistors with a large gate-width above 2 χ 50 μm, the transistors with a small gate-width exhibit unstable cryogenic behavior. The instability is suppressed by adding a source air-bridge. The stabilizing effect of the air-bridge is demonstrated both on device and circuit level. A three-stage 2440 GHz monolithic microwave integrated circuit (MMIC) LNA using a stabilized 100-nm HEMT technology is presented. The amplifier achieves a record noise temperature of 7 K at 25.6 GHz with an average noise of 10.6 K across the whole band at an ambient temperature of 5.5 K. The amplifier gain is 29 dB ± 0.6 dB exhibiting very stable and repeatable operation. To our knowledge, this amplifier presents the lowest noise temperature reported so far for InP cryogenic LNAs covering the Ka-band.
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20.
  • Cherednichenko, Serguei, 1970, et al. (författare)
  • A room temperature bolometer for terahertz coherent and incoherent detection
  • 2011
  • Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 1:2, s. 395 - 402
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a novel room temperature bolometer with nanosecond response that can be used both for coherent and incoherent detection through the entire terahertz frequency range. A responsivity of up to 15 V/W, and a noise equivalent power (NEP) = 450 pW/Hz0.5 were measured at modulation frequencies from 0.5 kHz to 100 kHz. A conversion gain of -28 dB was demonstrated at an intermediate frequency of 20 MHz with a Local Oscillator power of 0.74 mW. Possible improvements of the bolometer characteristics are discussed.
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21.
  • Cherednichenko, Serguei, 1970, et al. (författare)
  • Study of MgB2 HEB mixers vs the LO frequency and the bath temperature
  • 2015
  • Ingår i: 26th International Symposium on Space Terahertz Technology March 16-18, 2015, Cambridge, United States. ; , s. M2-1
  • Konferensbidrag (refereegranskat)abstract
    • We investigate the noise and the gain of MgB2 Hot-Electron Bolometer (HEB) mixers at 1.63THz LO. The critical temperature of the HEB was 22K and the film thickness was 20nm. At 4.2K and 12K bath temperatures the lowest obtained receiver noise temperatures are 1700K and 2100K,respectively, with a noise bandwidth of about 4.6GHz. The gain bandwidth is about 3GHz in both cases.
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22.
  • Cherednichenko, Serguei, 1970, et al. (författare)
  • THz Hot-Electron Bolometer Mixers
  • 2014
  • Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - 2162-2027 .- 2162-2035. - 9781479938773
  • Konferensbidrag (refereegranskat)abstract
    • We overview the technology of superconductingHot-Electron Bolometer mixers in the field of terahertzheterodyne detection. HEB mixer performance is analyzed vs competing technologies and application fields, with emphasize on radio astronomy. We discuss materials which have been reported in the past to be used for such devices with both phonon-substrate and electron-diffusion cooling mechanisms. It caused a splash of interesting theories with attempts of describing both dc and RF characteristics of HEB mixers. Development of HEB mixers made possible to extend high spectral resolution radio astronomy beyond 1THz.
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23.
  • Cherednichenko, Serguei, 1970, et al. (författare)
  • Wideband THz detectors based on YBCO thin films at 77K and at room temperature
  • 2011
  • Ingår i: 6th ESA Workshop on Millimetre-Wave Technology and Applications.
  • Konferensbidrag (refereegranskat)abstract
    • We present results of experimental investigation of THz direct detectors based on ultrathin YBCO films. The detectors are integrated with a spiral planar antenna. In the frequency band of 0.1-1.6THz the optical responsivity is from 170V/W for 77K. It increases to 400 V/W for operation temperature about 76K. The responsivity was constant up to 100kHz. Using mixing technique, the measured time constant is 0.5-2ns. Currently, at 77K, the NEP is 20pW/Hz0.5. At room temperature, the NEP is about 250pW/Hz0.5. For the same devices as coherent detector, the mixer gain was -21dB at 77K (and -28dB) at room temperature for an LO power of 0.4mW. With the present devices a mixer gain of up to -23dB is possible at 300K for an LO power of 1.5mW. Using smaller devices, similar gain can be achieved for a much smaller LO power.
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24.
  • Hammar, Arvid, 1986, et al. (författare)
  • Terahertz Direct Detection in YBa2Cu3O7 Microbolometers
  • 2011
  • Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 1:2, s. 390 - 394
  • Tidskriftsartikel (refereegranskat)abstract
    • A high sensitivity broadband terahertz direct detector based on YBa2Cu3O7 high-Tc superconductor microbolometers is presented. At 77 K, the responsivity of the spiral antenna-integrated microbolometers (1.5 um x 1.5 um) is 190 V/W, referenced to the input of the silicon substrate lens, across the frequency range of 330 GHz–1.63 THz in a single device. The response time is approximately 300 ps. Using a room temperature readout, we measure an optical noise equivalent power (NEP) of 20 pW/Hz^0.5 (readout noise limited) for modulation frequencies ranging from 500 Hz to 100 kHz.
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25.
  • Hammar, Arvid, 1986, et al. (författare)
  • Terahertz response of YBCO HEB homodyne detectors
  • 2011
  • Ingår i: 22nd International Symposium on Space Terahertz Technology 2011, ISSTT 2011; Tucson, AZ; United States; 25 April 2011 through 28 April 2011. ; , s. 81-
  • Konferensbidrag (refereegranskat)abstract
    • We report on the direct response of hot electron bolometers (HEB) used as homodyne detectors. These bolometers were tested at frequencies 0.1-1.6 THz and for a range of temperatures around 77 K. A logarithmic spiral antenna on a silicon lens was used, providing a broad frequency coverage (well above 1 THz). The measured responsivity ranged from 100 to 500 V/W depending on temperature and RF signal frequency, with RF signal power referenced at the input of the silicon lens. Corrections were made for losses in the cryostat window and polarization losses between the signal and antenna. The response time was about 3 ns. With the room temperature readout we estimate the noise equivalent power to be about 1 nW/Hz1/2. The bolometer bridges have nominal dimensions 1 μm x 2 μm x 50 nm and are fabricated on sapphire substrates using UV photolithography. A gas laser was used as source for 1.6 and 0.7 THz RF signals, backward wave oscillators at 0.5 THz and Gunn diodes at 0.1 THz. The obtained results show that YBCO bolometers have good prospects for various applications in the terahertz range as fast direct detectors as well as broadband mixers.
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26.
  • Hammar, Arvid, 1986, et al. (författare)
  • YBCO HEB THz mixers
  • 2011
  • Ingår i: 22nd International Symposium on Space Terahertz Technology 2011, ISSTT 2011; Tucson, AZ; United States; 25 April 2011 through 28 April 2011. ; , s. 82-
  • Konferensbidrag (refereegranskat)abstract
    • We report on an experimental investigation of high-Tc superconducting hot electron bolometer (HEB) mixers of YBCO. These mixers were tested at 100 and 530 GHz LO for a range of temperatures around 77 K. The conversion gain of -32 dB was measured at an LO power of about 1 mW (530 GHz) and 0.3 GHz IF. The mixers were integrated with a logarithmic spiral antenna on a silicon lens, providing a broad frequency coverage (well above 1 THz). To measure the incident RF signal power we used the homodyne responsivity (see abstract "Terahertz response of YBCO HEB homodyne detectors") which is referenced to the input of the silicon lens where the bolometers were glued. Corrections were made for losses in the cryostat window and polarization losses between the signal and antenna. We made the measurements at different temperatures and different LO power levels which were measured using a quasi optical detector at room temperature. The 3 dB gain bandwidth was measured to be about 0.2 GHz. The bolometer bridges have nominal dimensions 1 μm x 2 μm x 50 nm and are fabricated on sapphire substrates using UV photolithography. Backward wave oscillators sources were used at 530 GHz and Gunn diodes at 100 GHz.
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27.
  • Novoselov, Evgenii, 1988, et al. (författare)
  • Effect of the Critical and Operational Temperatures on the Sensitivity of MgB2 HEB Mixers
  • 2016
  • Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 6:2, s. 238-277
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we present a study of the noise and thegain of MgB hot-electron bolometer mixers with different critical temperatures and at various operation temperatures. At a local oscillator (LO) frequency of 1.63 THz the minimum input receiver noise temperature was 700 K with a gain of 18 dB for a device with a of 8.5 K. For a device with a of 22.5 K the corresponding values were 1700 K and 19 dB. For the latter device the was 2150 K at a bath temperature of 12 K, which is not achievable with Nb-compound based HEB mixers. We present and compare different methods for measurements of the HEB mixer gain and the output noise.
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28.
  • Novoselov, Evgenii, 1988, et al. (författare)
  • Noise measurements of the low Tc MgB2 HEB mixer at 1.6THz and 2.6THz
  • 2015
  • Ingår i: 26th International Symposium on Space Terahertz Technology March 16-18, 2015, Cambridge, United States. ; , s. P-31
  • Konferensbidrag (refereegranskat)abstract
    • We present results on MgB2 hot-electron bolometer noise measurements to show reproducibility of achieved results and robustness of the fabricated devices, which being passivated with silicon nitride shows the same performance after 1.5 year storing in nitrogen atmosphere. Noise temperature measurements were performed for the HEB made of 10nm MgB2 thin film on Al2O3 with Tc of 8.5K for 1.6THz LO at 2.7K and 4.2K. The minimum double side band noise temperatures corrected for optical losses for different bath temperatures were 700K and 1150K, whereas the noise bandwidth was 3.2GHz and 3.5GHz, respectively. The mixer output noise temperature and the conversion gain were 26K and -17.7dB, 27K and -14.9dB, respectively. For 2.6THz LO at 2.7K the corresponding values are 1200K and 3.7GHz.
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29.
  • Novoselov, Evgenii, 1988, et al. (författare)
  • THz Low Noise Mixers for Sub-mm Astronomy
  • 2016
  • Ingår i: Swedish Microwave Days March 15-16, 2016, Linköping, Sweden. ; , s. 50-
  • Konferensbidrag (refereegranskat)abstract
    • In this work we demonstrate that the MgB2 HEB mixer with a Tc of 22K can operate above 12K with just a 25% increase ofthe receiver noise temperature compared to that at 4.2 K. The GBW of 3.5 GHz was archived with a relatively thick film (a typical film thickness for NbN HEB mixers is 3–5 nm).
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