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Loudkov, D.; Tong, C.-Y. E.; Marrone, D. P.; Ryabchun, S.; Paine, S. N.; Blundell, R. |
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Title |
Transmission measurements of infrared filters for low-noise terahertz receiver applications |
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2005 |
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Proc. 16th Int. Symp. Space Terahertz Technol. |
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Proc. 16th Int. Symp. Space Terahertz Technol. |
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354-357 |
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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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Edward Tong, C.-Y.; Loudkov, Denis N.; Paine, Scott N.; Marrone, Dan P.; Blundell, Raymond |
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Title |
Vector measurement of the beam pattern of a 1.5 THz superconducting HEB receiver |
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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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453-456 |
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NbTiN HEB mixers |
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Near-field vector beam pattern of the 1.5 THz superconducting Hot Electron Bolometer (HEB) receiver currently in operation in Northern Chile has been performed in our laboratory. Using an open waveguide probe, we have mapped both the amplitude and phase of the beam emerging from our 1.5 THz HEB receiver package, across a number of planes along the line of propagation of the radio-beam. With an integration time of about 100 ms per point, a signal-to-noise ratio of about 25 dB was achieved for a beam waist of 3.5 mm. These measurements have proved to be invaluable in achieving good alignment between the cryostat housing the HEB mixer and the remainder of the receiver and telescope optics. The accuracy of our beam measurement is estimated to be ±0.2 mm in position and ±5 arc minutes in angular displacement. |
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1474 |
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Darula, Marian; Semenov, Alex D.; Hübers, Heinz-Wilhelm; Schubert, Josef |
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Title |
Quasioptical high-Tc superconductor Josephson mixer at terahertz frequencies |
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2000 |
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Proc. 11th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 11th Int. Symp. Space Terahertz Technol. |
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515 |
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HTS Josephson mixers |
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Mixers based on Josephson junctions from conventional superconductor materials have demonstrated excellent performance at subgap frequencies. The advantages of Josephson mixers are low optimal power of the local oscillator and large intermediate frequency bandwidth but their noise temperature increases dramatically at frequencies corresponding to the energy gap of the superconductor, which is typically below 1 THz for widely used materials. The large energy gap of oxide superconductors makes them promising candidates for development of terahertz Josephson mixers. Here we report on experimental study of the quasioptical mixer utilizing bicrystal Josephson junction from high-transition-temperature YBa 2 Cu 3 O 7-δ film. Junctions with a width of 2 µm were fabricated from 100 nm thick laser ablated films on bicrystal MgO substrates and had the and the J C R n product of about 2 mV at 4.2 K. The planar complementary logarithmic spiral antenna incorporated into co-planar waveguide was patterned from 200 nm thick gold film thermally evaporated in situ on top of the YBa 2 Cu 3 O 7-δ film. The mixer chip was clamped to the extended hemispherical silicon lens. Performance of the mixer was investigated at 4.5 K bath temperature. We used FIR laser as a local oscillator at frequencies 0.698 and 2.52 THz. System noise temperature (DSB) was determined from Y-factor measured with 300 K and 77 K loads. At 0.698 THz the lowest noise temperature 1750 K was observed when the mixer was biased with the fixed current to the region in the vicinity of either the first Shapiro step or the critical current. Between these two bias points the noise temperature increased to ≈ 20000 K. As function of the local oscillator power the noise temperature reached the minimum when the critical current was suppressed to the half of its equilibrium value. Power of the local oscillator absorbed by the mixer at optimal operation was of the order 100 nW. The present design of our antenna limits the upper operation frequency to the value of 1.8 THz. Nevertheless, we clearly observed Shapiro steps at the frequency 2.52 THz. Bearing in mind an improved design of the antenna, we estimate the 3000 K DSB noise temperature at this frequency. |
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1555 |
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Author |
Ekström, H.; Karasik, B.; Kollberg, E.; Yngvesson, K. S. |
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Title |
Investigation of a superconducting hot electron mixer |
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Conference Article |
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1994 |
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Proc. 5th Int. Symp. Space Terahertz Technol. |
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Proc. 5th Int. Symp. Space Terahertz Technol. |
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169-188 |
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HEB mixers |
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Mixing at 20 GHz in niobium superconducting thin film strips in the resistive state is studied. Experiments give evidence that electron-heating is the main cause of the non linear phenomena. The requirements on the mode of operation and on the film parameters for small conversion loss and the possibility of conversion gain are discussed. Measurements indicate a minimum intrinsic conversion loss around 1 dB with a sharp drop for the lowest voltage bias-points, and a DSB mixer noise temperature between 100 and 450 K at 20 GHz. The device output noise temperature at the mixer operating point can be as low as 30-50 K. A simple theory is presented, which is based on the assumption that the small signal resistance is linearly dependent on power. This type of mixer is considered very promising for use in low-noise heterodyne receivers at THz frequencies. |
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1642 |
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Author |
Elantev, Andrey I.; Karasik, Boris S. |
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Noise temperature of a superconducting hot-electron mixer |
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1994 |
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Proc. 5th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 5th Int. Symp. Space Terahertz Technol. |
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225 |
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HEB mixers |
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1645 |
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Sergeev, A. V.; Livanov, D. V. |
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Phonon renormalization of thermoelectric power of high-Tc materials |
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1993 |
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Phonon Scattering in Condensed Matter VII. Springer Series in Solid-State Sciences |
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Phonon Scattering in Condensed Matter VII. Springer Series in Solid-State Sciences |
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112 |
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204-205 |
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HTS, YBCO |
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Renormalization of thermoelectric power due to Nielsen — Taylor effect (interference between electron-phonon and electron- impurity interactions) is used for the explanation of the temperature dependence and sign of the thermopower in high-Tc materials. In the framework of the model the negative sign of TEP of untwinned YBa2Cu3O7−x crystal in a-direction observed by Howson et. al. is connected to the strong hole scattering via O-vacancies in chains. |
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Meissner, M.; Pohl, R. O. |
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Seventh International Conference, Cornell University, Ithaca, New York, August 3-7, 1992 |
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1664 |
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Budyanskij, M. Ya.; Sejdman, L. A.; Voronov, B. M.; Gubkina, T. O. |
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Increase of reproducibility in production of superconducting thin films of niobium nitride |
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1992 |
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Sverkhprovodimost': Fizika, Khimiya, Tekhnika |
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Sverkhprovodimost': Fizika, Khimiya, Tekhnika |
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5 |
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10 |
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1950-1954 |
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NbN films |
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Technique to control the composition of gas medium in the reactive magnetron discharge and the composition of the deposited films of niobium nitride using electrical parameters of discharge only, in particular, by δU = Up – Uar value at contant stabilized discharge current is described. Technique to select optimal condition for deposition of niobium nitride films when the films have composition meeting chemical formula, is suggested. Thin films of niobium nitride with up to 7 nm thickness and with rather high temperature of transition into superconducting state Tk > 10 K) and with low width of transition (δ < 0.6 K), are obtained. It is determined, that substrate material and dielectric sublayer do not affect. Tk value, while difference in coefficients of thermal expansion of substrate and of film affects δTk value. |
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0131-5366 |
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1675 |
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Gershenzon, E. M.; Orlova, S. L.; Orlov, L. A.; Ptitsina, N. G.; Rabinovich, R. I. |
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Intervalley cyclotron-impurity resonance of electrons in n-Ge |
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1976 |
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JETP Lett. |
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JETP Lett. |
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24 |
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3 |
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125-128 |
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n-Ge, cyclotron-impurity resonance |
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1730 |
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Mel’nikov, A. P.; Gurvich, Y. A.; Shestakov, L. N.; Gershenzon, E. M. |
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Magnetic field effects on the nonohmic impurity conduction of uncompensated crystalline silicon |
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2001 |
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Jetp Lett. |
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Jetp Lett. |
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73 |
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1 |
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44-47 |
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uncompensated crystalline silicon, nonohmic impurity conduction, magnetic field |
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The impurity conduction of a series of crystalline silicon samples with the concentration of major impurity N ≈ 3 × 1016 cm−3 and with a varied, but very small, compensation K was measured as a function of the electric field E in various magnetic fields H-σ(H, E). It was found that, at K < 10−3 and in moderate E, where these samples are characterized by a negative nonohmicity (dσ(0, E)/dE < 0), the ratio σ(H, E)/σ(0, E) > 1 (negative magnetoresistance). With increasing E, these inequalities are simultaneously reversed (positive nonohmicity and positive magnetoresistance). It is suggested that both negative and positive nonohmicities are due to electron transitions in electric fields from impurity ground states to states in the Mott-Hubbard gap. |
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0021-3640 |
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1752 |
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Гершензон, Е. М.; Грачев, С. А.; Литвак-Горская, Л. Б. |
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Механизм преобразования частоты в n-InSb-смесителе |
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1991 |
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Физика и техника полупроводников |
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Физика и техника полупроводников |
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25 |
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11 |
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1986-1998 |
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n-InSb mixer |
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Проведено комплексное исследование n-InSb смесителя на λ=2.6 мм, включающее в себя исследование вольт-амперных характеристик при E=0−2 В/см, температурной зависимости проводимости в диапазоне T=1.6−20 K, высокочастотной проводимости при f=0.5−10 МГц и магнитосопротивления при H=0−5 кЭ. Показано, что в оптимальном режиме механизм преобразования частоты связан с фотоионизационными процессами при прыжковой фотопроводимости (ПФП). На основе модели ПФП рассчитан коэффициент преобразования смесителя и произведено сопоставление его с экспериментом. Показана несостоятельность модели преобразования частоты в компенсированном n-InSb (K≥0.8), основанной на разогреве электронов. Обсуждены требования к параметрам материала и режимам n-InSb смесителя миллиметрового диапазона волн. |
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