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| Author |
Trifonov, A.; Tong, C.-Y. E.; Lobanov, Y.; Kaurova, N.; Blundell, R.; Goltsman, G. |
| Title |
Gap frequency and photon absorption in a hot electron bolometer |
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Conference Article |
| Year |
2016 |
Publication |
Proc. 27th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 27th Int. Symp. Space Terahertz Technol. |
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121 |
| Keywords |
NbN HEB; Si membrane |
| Abstract |
The superconducting energy gap is a crucial parameter of a superconductor when used in mixing applications. In the case of the SIS mixer, the mixing process is efficient for frequencies below the energy gap, whereas, in the case of the HEB mixer, the mixing process is most efficient at frequencies above the gap, where photon absorption takes place more readily. We have investigated the photon absorption phenomenon around the gap frequency of HEB mixers based on NbN films deposited on silicon membranes. Apart from studying the pumped I-V curves of HEB devices, we have also probed them with microwave radiation, as previously described [1]. At frequencies far below the gap frequency, the pumped I-V curves show abrupt switching between the superconducting and resistive states. For the NbN HEB mixers we tested, which have critical temperatures of ~9 K, this is true for frequencies below about 400 GHz. As the pump frequency is increased beyond 400 GHz, the resistive state extends towards zero bias and at some point a small region of negative differential resistance appears close to zero bias. In this region, the microwave probe reveals that the device impedance is changing randomly with time. As the pump frequency is further increased, this random impedance change develops into relaxation oscillations, which can be observed by the demodulation of the reflected microwave probe. Initially, these oscillations take the form of several frequencies grouped together under an envelope. As we approach the gap frequency, the multiple frequency relaxation oscillations coalesce into a single frequency of a few MHz. The resultant square-wave nature of the oscillation is a clear indication that the device is in a bi-stable state, switching between the superconducting and normal state. Above the gap frequency, it is possible to obtain a pumped I-V curve with no negative differential resistance above a threshold pumping level. Below this pumping level, the device demonstrates bi-stability, and regular relaxation oscillation at a few MHz is observed as a function of pump power. The threshold pumping level is clearly related to the amount of power absorbed by the device and its phonon cooling. From the above experiment, we can derive the gap frequency of the NbN film, which is 585 GHz for our 6 μm thin silicon membrane-based device. We also confirm that the HEB mixer is not an efficient photon absorber for radiation below the gap frequency. 1. A. Trifonov et al., “Probing the stability of HEB mixers with microwave injection”, IEEE Trans. Appl. Supercond., vol. 25, no. 3, June 2015. |
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1204 |
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Lobanov, Y.; Tong, C.; Blundell, R.; Gol'tsman, G. |
| Title |
A study of direct detection effect on the linearity of hot electron bolometer mixers |
Type |
Conference Article |
| Year |
2009 |
Publication |
Proc. 20th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 20th ISSTT |
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Pages |
282-287 |
| Keywords |
HEB mixer, direct detection effect |
| Abstract |
We have performed a study of how direct detection affects the linearity and hence the calibration of an HEB mixer. Two types of waveguide HEB devices have been used: a 0.8 THz HEB mixer and a 1.0 THz HEB mixer which is ~5 times smaller than the former. Two independent experimental approaches were used. In the ΔG/G method, the conversion gain of the HEB mixer is first measured as a function of the bias current for a number of bias voltages. At each bias setting, we carefully measure the change in the operating current when the input loads are switched. From the measured data, we can derive the expected difference in gain between the hot and cold loads. In the second method (injection method [1]), the linearity of the HEB mixer is independently measured by injecting a modulated signal for different input load temperatures. The results of both approaches confirm that there is gain compression in the operation of HEB mixers. Based on the results of our measurements, we discuss the impact of direct detection effects on the operation of HEB mixers. |
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RPLAB @ gujma @ |
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724 |
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Loudkov, D.; Tong, C.-Y.E.; Blundell, R.; Kaurova, N.; Grishina, E.; Voronov, B.; Gol’tsman, G. |
| Title |
An investigation of the performance of the waveguide superconducting HEB mixer at different RF embedding impedances |
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Conference Article |
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2005 |
Publication |
Proc. 16th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 16th Int. Symp. Space Terahertz Technol. |
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226-229 |
| Keywords |
waveguide NbN HEB mixers |
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We have conducted an investigation of the performance of superconducting hot-electron bolometric (HEB) mixer at 800 GHz as a function of the embedding impedance of the waveguide embedding circuit. Using a single half-height mixer block, we have developed three different mixer chip configurations, offering nominal embedding resistances of 70, 35, and 15 Ohms. Both the High Frequency Structure Simulator (HFSS) software and scaled model impedance measurements were employed in the design process. Two batches of HEB mixers were fabricated to these designs using 3-4 nm thick NbN thin film. The mixers were characterized through receiver noise temperature measurements and Fourier Transform Spectrometer (FTS) scans. Briefly, a minimum receiver noise temperature of 440 K was measured at a local oscillator frequency 850 GHz for a mixer of normal state resistance 62 Ohms incorporated into a circuit offering a nominal embedding impedance of 70 Ohms. We conclude from our data that, for low noise operation, the normal state resistance of the HEB mixer element should be close to that of the embedding impedance of the mixer mount. |
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1472 |
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Loudkov, D.; Tong, C.-Y. E.; Marrone, D. P.; Ryabchun, S.; Paine, S. N.; Blundell, R. |
| Title |
Transmission measurements of infrared filters for low-noise terahertz receiver applications |
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Conference Article |
| Year |
2005 |
Publication |
Proc. 16th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 16th Int. Symp. Space Terahertz Technol. |
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Pages |
354-357 |
| Keywords |
FTS, Zitex, alkali halide, crystalline quartz, Parylene, polyethylene, IR filters, transmission, THz applications |
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Infrared (IR) filters are very important to the efficient operation of cryogenic receivers. Usually, such filters are mounted on the radiation shield of the cryostat to reduce the heat load to the 4 K stage. Insufficient filtering may cause the temperature of the mixing element in a receiver to be excessively warm, leading to degradation in sensitivity. These filters should be effective in blocking the room temperature IR radiation from outside the cryostat, yet should be transparent across the desired signal frequency band. In the Terahertz frequency range, which is close to the infrared, it is difficult to find an inexpensive low- loss material that can provide the required IR blocking capacity. We present transmission measurements, made using a Fourier Transform Spectrometer (FTS), of a number of potential infrared filters between 0.4 and 1.6 THz. The filters tested include the widely-used, Teflon-based, Zitex-A and Zitex-G films, alkali halide based infrared filter, and crystalline quartz coated with Parylene, and polyethylene films. |
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1473 |
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Meledin, D.; Tong, C. Y.-E.; Blundell, R.; Kaurova, N.; Smirnov, K.; Voronov, B.; Gol'tsman, G. |
| Title |
The sensitivity and IF bandwidth of waveguide NbN hot electron bolometer mixers on MgO buffer layers over crystalline quartz |
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Conference Article |
| Year |
2002 |
Publication |
Proc. 13th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 13th Int. Symp. Space Terahertz Technol. |
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Pages |
65-72 |
| Keywords |
waveguide NbN HEB mixers |
| Abstract |
We have developed and characterized waveguide phonon-cooled NbN Hot Electron Bolometer (FMB) mixers fabricated from a 3-4 nm thick NbN film deposited on a 200nm thick MgO buffer layer over crystalline quartz. Double side band receiver noise temperatures of 900-1050 K at 1.035 THz, and 1300-1400 K at 1.26 THz have been measured at an intermediate frequency of 1.5 GHz. The intermediate frequency bandwidth, measured at 0.8 THz LO frequency, is 3.2 GHz at the optimal bias point for low noise receiver operation. |
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Cambridge, MA, USA |
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Harvard university |
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326 |
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Kawamura, J.; Blundell, R.; Tong, C-Y. E.; Gol'tsman, G.; Gershenzon, E.; Voronov, B.; Cherednichenko, S. |
| Title |
Phonon-cooled NbN HEB mixers for submillimeter wavelengths |
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Conference Article |
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1997 |
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Proc. 8th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 8th Int. Symp. Space Terahertz Technol. |
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23-28 |
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waveguide NbN HEB mixers |
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The noise performance of receivers incorporating NbN phonon-cooled superconducting hot electron bolometric mixers is measured from 200 GHz to 900 GHz. The mixer elements are thin-film (thickness — 4 nm) NbN with —5 to 40 pm area fabricated on crystalline quartz sub- strates. The receiver noise temperature from 200 GHz to 900 GHz demonstrates no unexpected degradation with increasing frequency, being roughly TRx ,; 1-2 K The best receiver noise temperatures are 410 K (DSB) at 430 GHz, 483 K at 636 GHz, and 1150 K at 800 GHz. |
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275 |
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Kawamura, J.; Blundell, R.; Tong, C.-Y. E.; Golts'man, G.; Gershenzon, E.; Voronov B. |
| Title |
Superconductive NbN hot-electron bolometric mixer performance at 250 GHz |
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Conference Article |
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1996 |
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Proc. 7th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 7th Int. Symp. Space Terahertz Technol. |
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331-336 |
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NbN HEB mixers |
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Thin film NbN (<40 A) strips are used as waveguide mixer elements. The electron cooling mechanism for the geometry is the electron-phonon interaction. We report a receiver noise temperature of 750 K at 244 GHz, with / IF = 1.5 GHz, Af= 500 MHz, and Tphysical = 4 K. The instantaneous bandwidth for this mixer is 1.6 GHz. The local oscillator (LO) power is 0.5 1.tW with 3 dB-uncertainty. The mixer is linear to 1 dB up to an input power level 6 dB below the LO power. We report the first detection of a molecular line emission using this class of mixer, and that the receiver noise temperature determined from Y-factor measurements reflects the true heterodyne sensitivity. |
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945 |
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Kawamura, J.; Blundell, R.; Tong, C.-Y. E.; Gol'tsman, G.; Gershenzon, E.; Voronov, B. |
| Title |
NbN hot-electron mixer measurements at 200 GHz |
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Conference Article |
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1995 |
Publication |
Proc. 6th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 6th Int. Symp. Space Terahertz Technol. |
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254-261 |
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NbN HEB mixers |
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We present noise and gain measurements of resistively driven NbN hot-electron mixers near 200 GHz. The device geometry is chosen so that the dominant cooling process of the hot-electrons is their interaction with the lattice. Except for a single batch, the intermediate frequency cut-off of these mixer elements is – 3 700 MHz, and has shown little variation among other batches of devices. At 100 MHz we measured intrinsic mixer losses as low as —3 dB. We measured the noise temperatures at several intermediate frequencies, and for the best de- vice at 137 MHz with 20 MHz bandwidth, we measured 2000 K; using a low-noise first- stage amplifier at 1.5 GHz with 200 MHz bandwidth, the receiver noise temperature measured 2800 K. We estimate that the noise contribution from the mixer is 500 K and the total losses are —15 dB at 137 MHz. |
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1626 |
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Kawamura, J.; Hunter, T. R.; Tong, C. Y. E.; Blundell, R.; Papa, D. C.; Patt, F.; Peters, W.; Wilson, T.; Henkel, C.; Goltsman, G.; Gershenzon, E. |
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Ground-based terahertz CO spectroscopy towards Orion |
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Journal Article |
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2002 |
Publication |
A&A |
Abbreviated Journal |
A&A |
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394 |
Issue |
1 |
Pages |
271-274 |
| Keywords |
HEB mixers, applications |
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Using a superconductive hot-electron bolometer heterodyne receiver on the 10-m Heinrich Hertz Telescope on Mount Graham, Arizona, we have obtained velocity-resolved 1.037 THz CO () spectra toward several positions along the Orion Molecular Cloud (OMC-1) ridge. We confirm the general results of prior observations of high-J CO lines that show that the high temperature, , high density molecular gas, , is quite extended, found along a ~ region centered on BN/KL. However, our observations have significantly improved angular resolution, and with a beam size of we are able to spatially and kinematically discriminate the emission originating in the extended quiescent ridge from the very strong and broadened emission originating in the compact molecular outflow. The ridge emission very close to the BN/KL region appears to originate from two distinct clouds along the line of sight with and ≈ . The former component dominates the emission to the south of BN/KL and the latter to the north, with a turnover point coincident with or near BN/KL. Our evidence precludes a simple rotation of the inner ridge and lends support to a model in which there are multiple molecular clouds along the line of sight towards the Orion ridge. |
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322 |
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Kawamura, J. H.; Tong, C.-Y.E.; Blundell, R.; Cosmo Papa, D.; Hunter, T. R.; Gol'tsman, G.; Cherednichenko, S.; Voronov, B.; Gershenzon, E. |
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An 800 GHz NbN phonon-cooled hot-electron bolometer mixer receiver |
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Journal Article |
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1999 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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9 |
Issue |
2 |
Pages |
3753-3756 |
| Keywords |
NbN HEB mixers |
| Abstract |
We describe a heterodyne receiver developed for astronomical applications to operate in the 350 /spl mu/m atmospheric window. The waveguide receiver employs a superconductive NbN phonon-cooled hot-electron bolometer mixer. The double sideband receiver noise temperature closely follows 1 kGHz/sup -1/ across 780-870 GHz, with the intermediate frequency centered at 1.4 GHz. The conversion loss is about 15 dB. The receiver was installed for operation at the University of Arizona/Max Planck Institute for Radio Astronomy Submillimeter Telescope facility. The instrument was successfully used to conduct test observations of a number of celestial sources in a number of astronomically important spectral lines. |
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1051-8223 |
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288 |
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