| Records |
Author  |
de Lange, G.; Kuipers, J. J.; Klapwijk, T. M.; Panhuyzen, R. A.; van de Stadt, H.; de Graauw, M. W. M. |
| Title |
Superconducting resonator circuits at frequencies above the gap frequency |
Type |
Journal Article |
| Year |
1995 |
Publication |
J. Appl. Phys. |
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77 |
Issue |
4 |
Pages |
1795-1804 |
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257 |
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Ekstrom H.; Karasik B. S.; Kollberg E.L.; Yngvesson K.S. |
| Title |
Conversion Gain and Noise of Niobium Superconducting Hot-Electron-Mixers |
Type |
Journal Article |
| Year |
1995 |
Publication |
IEEE Trans. Microw. Theory Techn. |
Abbreviated Journal |
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| Volume |
43 |
Issue |
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Pages |
938-947 |
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A study has been done of microwave mixing at 20 GHz using the nonlinear (power dependent) resistance of thin niobium strips in the resistive state. Our experiments give evidence that electron-heating is the main cause of the nonlinear phenomenon. Also a detailed phenomenological theory for the determination of conversion properties is presented. This theory is capable of predicting the frequency-conversion loss rather accurately for arbitrary bias by examining the I-V-characteristic. Knowing the electron temperature relaxation time, and using parameters derived from the I-V-characteristic also allows us to predict the -3-dB IF bandwidth. Experimental results are in excellent agreement with the theoretical predictions. The require ments on the mode of operation and on the film parameters for minimizing the conversion loss (and even achieving conversion gain) are discussed in some detail. Our measurements demon-strate an intrinsic conversion loss as low as 1 dB. The maximum IF frequency defined for -3-dB drop in conversion gain, is about 80 MHz. Noise measurements indicate a device output noise temperature of about 50 K and SSB mixer noise temperature below 250 K. This type of mixer is considered very promising for use in low-noise heterodyne receivers at THz frequencies. |
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RPLAB @ atomics90 @ |
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964 |
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| Author |
Ekström, H.; Karasik, B.; Kollberg, E.; Gol'tsman, G.; Gershenzon, E. |
| Title |
350 GHz NbN hot electron bolometer mixer |
Type |
Conference Article |
| Year |
1995 |
Publication |
Proc. 6th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 6th Int. Symp. Space Terahertz Technol. |
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Issue |
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Pages |
269-283 |
| Keywords |
NbN HEB mixers |
| Abstract |
Superconducting NbN hot-electron bolometer (HEB) mixer devices have been fabricated and measured at 350 GHz. The HEB is integrated with a double dipole antenna on an extended crystalline quartz hyper hemispherical substrate lens. Heterodyne measurement gave a -3 dB bandwidth, mainly determined by the electron- phonon interaction time, of about 680 and 1000 MHz for two different films with Tc = 8.5 and 11 K respectively. The measured DSB receiver noise temperature is around 3000 K at 800 MHz IF frequency. The main contribution to the output noise from the device is due to electron temperature fluctuations with the equivalent output noise temperature TFL-100 K. TH, has the same frequency dependence as the IF response. The contribution from Johnson noise is of the order of T. The RF coupling loss is estimated to be = 6 dB. The film with lower Tc, had an estimated intrinsic low-frequency conversion loss = 7 dB, while the other film had a conversion loss as high as 14 dB. The difference in intrinsic conversion loss is explained by less uniform absorption of radiation. Measurements of the small signal impedance shows a transition of the output impedance from the DC differential resistance Rd=dV/dI in the low frequency limit to the DC resistance R 0 =Uoff 0 in the bias point for frequencies above 3 GHz. We judge that the optimum shape of the IV-characteristic is more easily obtained at THz frequencies where the main restriction in performance should come from problems with the RF coupling. |
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1628 |
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Gerecht, E.; Musante, C. F.; Schuch, R.; Lutz, C. R.; Jr.; Yngvesson, K. S.; Mueller, E. R.; Waldivian, J.; Gol'tsman, G. N.; Voronov, B. M.; Gershenzon, E. M. |
| Title |
Hot electron detection and mixing experiments in NbN at 119 micrometer wavelength |
Type |
Conference Article |
| Year |
1995 |
Publication |
Proc. 6th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 6th Int. Symp. Space Terahertz Technol. |
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Issue |
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Pages |
284-293 |
| Keywords |
NbN HEB mixers, detectors |
| Abstract |
We have performed preliminary experiments with the goal of demonstrating a Hot Electron Bolometric (HEB) mixer for a 119 micrometer wavelength (2.5 THz). We have chosen a NbN device of size 700 x 350 micrometers. This device can easily be coupled to a laser LO source, which is advantageous for performing a prototype experiment. The relatively large size of the device means that the LO power required is in the mW range; this power can be easily obtained from a THz laser source. We have measured the amount of laser power actually absorbed in the device, and from this have estimated the best optical coupling loss to be about 10 di . We are developing methods for improving the optical coupling further. Preliminary measurements of the response of the device to a chopped black-body have not yet resulted in a measured receiver noise temperature. We expect to be able to complete this measurement in the near future. |
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1629 |
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Gol'tsman, G. N.; Karasik, B. S.; Okunev, O. V.; Dzardanov, A. L.; Gershenzon, E. M.; Ekstrom, H.; Jacobsson, S.; Kollberg, E. |
| Title |
NbN hot electron superconducting mixers for 100 GHz operation |
Type |
Journal Article |
| Year |
1995 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
| Volume |
5 |
Issue |
2 |
Pages |
3065-3068 |
| Keywords |
NbN HEB mixers |
| Abstract |
NbN is a promising superconducting material for hot-electron superconducting mixers with an IF bandwidth larger than 1 GHz. In the 1OO GHz frequency range, the following parameters were obtained for 50 /spl Aring/ thick NbN films at 4.2 K: receiver noise temperature (DSB) /spl sim/1000 K; conversion loss /spl sim/10 dB; IF bandwidth /spl sim/1 GHz; and local oscillator power /spl sim/1 /spl mu/W. An increase of the critical current of the NbN film, increased working temperature, and a better mixer matching may allow a broader IF bandwidth up to 2 GHz, reduced conversion losses down to 3-5 dB and a receiver noise temperature (DSB) down to 200-300 K. |
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1051-8223 |
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| Notes |
About LO power required |
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no |
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Serial |
255 |
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Gol'tsman, G. N.; Karasik, B. S.; Svechnikov, S. I.; Gershenzon, E. M.; Ekström, H.; Kollberg E. |
| Title |
Noise temperature of NbN hot—electron quasioptical superconducting mixer in 200-700 GHz range |
Type |
Abstract |
| Year |
1995 |
Publication |
Proc. 6th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 6th Int. Symp. Space Terahertz Technol. |
| Volume |
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Issue |
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Pages |
268 |
| Keywords |
NbN HEB mixers, noise temperature |
| Abstract |
The electron heating effect in superconducting films is becoming very attractive for the development of THz range mixers because of the absence of frequency limitations inherent in the bolometric mechanism. However, the evidence for the spectral dependence of the position of optimal operating point has been found recently for NbN thin film devices 1.2 • The effect is presumably attributed to the variation in the absorption of radiation depending on the frequency. Since the resistive state is not spatially uniform the coupling efficiency of the mixer device with radiation can be different for frequencies larger than Zeilh and those smaller than 2Alh (d is the effective superconducting gap in the resistive state). To study the effect more thoroughly we have investigated the noise temperature of quasioptical NbN mixer device with broken hue tapered slot antenna in the frequency range 200-700 GHz. The device consists of several (5-10) parallel strips 1 jim wide and 6-7 tun thick made from NbN film on Si0 2 -Si 3 N 4 -Si membrane. The strips are connected with the gold contacts of the slot-line antenna which serves both as bias and IF leads. We used backward wave oscillators as LO sources and a standard hot/cold load technique for noise temperature measurements. The frequency dependence of noise temperature is mainly determined by two factors: frequency properties of the antenna and frequency dependence of the NbN film impedance. To separate both factors we monitored the frequency dependence of the device responsivity in the detector mode at a higher temperature within the superconducting transition where the impedance of NbN film is close to its normal resistance. In this case the impedance of the device itself is frequency independent. The experimental results will be reported at the Symposium. 1. G. Gollsman, S. Jacobsson, H. EkstrOm, B. Karasik, E. Kollberg, and E. Gershenzon, “Slot-line tapered antenna with NbN hot electron mixer for 300-360 GHz operation,” Proc of the 5th Int. Symp. on Space Terahertz Technology, pp. 209-213a, May 10-12,1994. 2. B.S. Karasik, G.N. Gol i tsman, B.M. Voronov, S.I. Svechnikov, E.M. Gershenzon, H. Ekstrom, S. Jacobsson, E. Kollberg, and K.S. Yngvesson, “Hot electron quasioptical NbN superconducting mixer,” presented at the ASC94, submitted to IEEE Trans. on Appl. Superconductivity. |
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no |
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1627 |
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| Author |
Gol'tsman, G.; Kouminov, P.; Goghidze, I.; Gershenzon, E. |
| Title |
Nonequilibrium kinetic inductive response of YBCO thin films to low power laser pulses |
Type |
Journal Article |
| Year |
1995 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
| Volume |
5 |
Issue |
2 |
Pages |
2591-2594 |
| Keywords |
YBCO HTS KID |
| Abstract |
We have discovered a transient nonequilibrium kinetic inductive voltage response of YBCO thin films to 20 ps pulses of YAG:Nd laser radiation with 0.63 /spl mu/m and 1.54 /spl mu/m wavelength. By increasing the sensitivity of the read-out system with 100 ps resolution time and diminishing the light intensity (fluence 0.1-2 /spl mu/J/cm/sup 2/) and transport current (density /spl les/10/sup 5/ A/cm/sup 2/) we were able to observe a peculiar bipolar signal form with nearly equal amplitudes for each sign. The integration of the kinetic inductive response over time gives the result which is qualitatively, of the same form as the response in the resistive and normal states: the nonequilibrium picosecond scale component is followed by the bolometric nanosecond component. The nonequilibrium response is interpreted as suppression of the order parameter by excess quasiparticles followed by a change both in resistance (for the resistive state) and in kinetic inductance (for the superconducting state). |
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1051-8223 |
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no |
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1621 |
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| Author |
Hans Ekstrom; Karasik, Boris S.; Kollberg, Erik L.; Sigfrid Yngvesson |
| Title |
Conversion gain and noise of niobium superconducting hot–electron–mixers |
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Journal Article |
| Year |
1995 |
Publication |
IEEE Trans. Appl. Supercond. |
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| Volume |
43 |
Issue |
4 |
Pages |
938-947 |
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Nb HEB mixers |
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254 |
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Hesler, J. L.; Crowe, T. W.; Bradley, R. F.; Pan, S. K.; Chattopadhyay, G. |
| Title |
The design, construction and evaluation of a 585 GHz planar Schottky mixer |
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Conference Article |
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1995 |
Publication |
Proc. 6th Int. Symp. Space Terahertz Technol. |
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34-43 |
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Pasadena, Ca |
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259 |
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Karasik, B. S.; Elantiev, A. I. |
| Title |
Analysis of the noise performance of a hot-electron superconducting bolometer mixer |
Type |
Conference Article |
| Year |
1995 |
Publication |
Proc. 6th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 6th Int. Symp. Space Terahertz Technol. |
| Volume |
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Issue |
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Pages |
229-246 |
| Keywords |
HEB mixers |
| Abstract |
A theoretical analysis for the noise temperature of hot–electron superconducting mixer has been presented. Thecontributions of both Johnson noise and electron temperature fluctuations have been evaluated. A set of criteriaensuring low noise performance of the mixer has been stated and a simple analytic expression for the noisetemperature of the mixer device has been suggested. It has been shown that an improvement of the mixer sensitivitydoes not necessarily follow by a decrease of the bandwidth. An SSB noise temperature limit due to the intrinsic noisemechanisms has been estimated to be as low as 40–90 K for a mixer device made from Nb or NbN thin film.Furthermore, the conversion gain bandwidth can be as wide as is allowed by the intrinsic electron temperaturerelaxation time if an appropriate choice of the mixer resistance has been made. The intrinsic mixer noise bandwidthis of 3 GHz for Nb device and of 5 GHz for NbN device. An additional improvement of the theory has been madewhen a distinction between the impedance measured at high intermediate frequency (larger than the mixerbandwidth) and the mixer ohmic resistance has been taken into account.Recently obtained experimental data on Nb and NbNbolometer mixer devices are viewed in connection with thetheoretical predictions.The noise temperature limit has also been specified for the mixer device where an outdiffusion coolingmechanism rather than the electron–phonon energy relaxation determines the mixer bandwidth. A consideration ofthe noise performance of a bolometer mixer made from YBaCuO film utilizing a hot–electron effect has been done. |
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Pasadena, Ca |
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258 |
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Karasik, B. S.; Gol'tsman, G. N.; Voronov, B. M.; Svechnikov, S. I.; Gershenzon, E. M.; Ekstrom, H.; Jacobsson, S.; Kollberg, E.; Yngvesson, K. S. |
| Title |
Hot electron quasioptical NbN superconducting mixer |
Type |
Journal Article |
| Year |
1995 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
| Volume |
5 |
Issue |
2 |
Pages |
2232-2235 |
| Keywords |
NbN HEB mixers |
| Abstract |
Hot electron superconductor mixer devices made of thin NbN films on SiO/sub 2/-Si/sub 3/N/sub 4/-Si membrane have been fabricated for 300-350 GHz operation. The device consists of 5-10 parallel strips each 5 /spl mu/m long by 1 /spl mu/m wide which are coupled to a tapered slot-line antenna. The I-V characteristics and position of optimum bias point were studied in the temperature range 4.5-8 K. The performance of the mixer at higher temperatures is closer to that predicted by theory for uniform electron heating. The intermediate frequency bandwidth versus bias has also been investigated. At the operating temperature 4.2 K a bandwidth as wide as 0.8 GHz has been measured for a mixer made of 6 nm thick film. The bandwidth tends to increase with operating temperature. The performance of the NbN mixer is expected to be better for higher frequencies where the absorption of radiation should be more uniform. |
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1051-8223 |
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1622 |
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Karasik, B. S.; Milostnaya, I. I.; Zorin, M. A.; Elantev, A. I.; Gol'tsman, G. N.; Gershenzon, E. M. |
| Title |
High speed current switching of homogeneous YBaCuO film between superconducting and resistive states |
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Journal Article |
| Year |
1995 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
| Volume |
5 |
Issue |
2 |
Pages |
3042-3045 |
| Keywords |
YBCO HTS HEB switches |
| Abstract |
Transitions of thin structured YBaCuO films from superconducting (S) to normal (N) state and back induced by a supercritical current pulse has been studied. A subnanosecond stage in the film resistance dynamic has been observed. A more gradual (nanosecond) ramp in the time dependence of the resistance follows the fast stage. The fraction of the film resistance which is attained during the fast S-N stage rises with the current amplitude. Subnanosecond N-S switching is more pronounced for smaller amplitudes of driving current and for shorter pulses. The phenomena observed are viewed within the framework of an electron heating model. The expected switching time and repetition rate of an optimized current controlling device are estimated to be 1-2 ps and 80 GHz respectively. |
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1051-8223 |
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no |
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1620 |
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Karasik, B. S.; Zorin, M. A.; Milostnaya, I. I.; Elantev, A. I.; Gol’tsman, G. N.; Gershenzon, E. M. |
| Title |
Subnanosecond switching of YBaCuO films between superconducting and normal states induced by current pulse |
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Journal Article |
| Year |
1995 |
Publication |
J. Appl. Phys. |
Abbreviated Journal |
J. Appl. Phys. |
| Volume |
77 |
Issue |
8 |
Pages |
4064-4070 |
| Keywords |
YBCO HTS switches |
| Abstract |
A study is reported of the current switching in high‐quality YBaCuO films deposited onto NdGaO3 and ZrO2 substrates between superconducting (S) and normal (N) states. The films 60–120 nm thick prepared by laser ablation were structured into single strips between gold contacts. The time dependence of the resistance after application of the voltage step to the film was monitored. Experiment performed within certain ranges of voltage amplitudes and temperatures has shown the occurrence of the fast stage (shorter than 400 ps) both in S‐N and N‐S transitions. A fraction of the film resistance changing within this stage in the S‐N transition increases with the current amplitude. A subnanosecond N‐S stage becomes more pronounced for shorter pulses. The fast switching is followed by the much slower change of resistance. The mechanism of switching is discussed in terms of the hot‐electron phenomena in YBaCuO. The contributions of other thermal processes (e.g., a phonon escape from the film, a heat diffusion in the film and substrate, a resistive domain formation) in the subsequent stage of the resistance dynamic have been also discussed. The basic limiting characteristics (average dissipated power, energy needed for switching, maximum repetition rate) of a picosecond switch which is proposed to be developed are estimated. |
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0021-8979 |
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1623 |
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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 |
Type |
Conference Article |
| Year |
1995 |
Publication |
Proc. 6th Int. Symp. Space Terahertz Technol. |
Abbreviated Journal |
Proc. 6th Int. Symp. Space Terahertz Technol. |
| Volume |
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Issue |
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Pages |
254-261 |
| Keywords |
NbN HEB mixers |
| Abstract |
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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Kerr, A. R. |
| Title |
Some fundamental and practical limits on broadband matching tocapacitive devices, and the implications for SIS mixer design |
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1995 |
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IEEE Trans. Microw. Theory Techn. |
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43 |
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1 |
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2-13 |
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256 |
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Krasnosvobodtsev, S. I.; Shabanova, N,P.; Ekimov, E.V.; Nozdrin, V.S.; Pechen, E,V. |
| Title |
Critical magnetic field of NbC: new data on clean superconductor films |
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Journal Article |
| Year |
1995 |
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Abbreviated Journal |
Zh. Eks. Teor.Fiz. |
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Pages |
534-537 |
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The temperature dependence of the upper critical magnetic fields of exceptionally low-defect-density films of the superconducting compound NbC has been investigated, and previously unknown parameters of this clean superconductor and its electronic characteristics have been evaluated. An electron density of states at the Fermi level equal to 1.3 states/ eV. Nb atom, a Fermi velocity equal to 2.2X lo7 cmls, a plasma frequency equal to 3.6 eV, and a coherence length to 24 nm have been obtained with an electron mean free path exceeding 40 nm. A vortex-free state existing over the entire temperature range below T, which causes a many-fold increase in the critical magnetic field of the films when the field is aligned parallel to their surface, has been discovered in very thin films of superconducting niobium carbide. |
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RPLAB @ atomics90 @ |
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956 |
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Okunev, 0.; Dzardranov, A.; Gol'tsman, G.; Gershenzon, E. |
| Title |
Performances of hot—electron superconducting mixer for frequencies less than the gap energy: NbN mixer for 100 GHz operation |
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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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247-253 |
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NbN HEB mixers |
| Abstract |
The possibilities to improve the parameters of the 100 GHz NbN HEB superconducting waveguide mixers have been studied. The device consists of a signal strip 1 gm wide by 2 Am long made of 40 A thick NbN film. The best operation point was found at 5 K, where the mixer bandwidth made up 1.5-2 GHz and the total loss diminished down to 8 dB. The critical current density has been increased up to " 40 6 A/cm 2 , the noise temperature of the receiver (DSB) has reduced down to 450 K and the local oscillator power has decreased down to -.4).1 mcV. |
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1625 |
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| Author |
Parvitte, B.; Thomas, X.; Courtois, D. |
| Title |
Wide band (2.5 GHz) infrared heterodyne spectrometer |
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Journal Article |
| Year |
1995 |
Publication |
Int. J. Infrared and Millimeter Waves |
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16 |
Issue |
9 |
Pages |
1533-1540 |
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HgCdTe detector mixer |
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0195-9271 |
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no |
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470 |
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Ptitsina, N. G.; Chulkova, G. M.; Gershenzon, E. M. |
| Title |
Influence of the interference of electron-phonon and electron-impurity scattering on the conductivity of unordered Nb films |
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Journal Article |
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1995 |
Publication |
JETP |
Abbreviated Journal |
JETP |
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80 |
Issue |
5 |
Pages |
960-964 |
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The temperature dependence of the resistivity of Nb thin films has been studied at T=4.2-300 K. It has been shown that quantum interference between electron-phonon and electron-impurity scattering determines the temperature dependence of the resistivity of the films investigated over a broad temperature range. The magnitude of the contribution of the electron-phonon-impurity,interference is described satisfactorily by the theory developed by Reizer and Sergeev {Zh. Eksp. Teor. Fiz. 92,2291 (1987) [Sov. Phys. JETP 65, 1291 (1987)l). The interaction constants of electrons with longitudinal and transverse phonons in Nb films have been determined for the first time by comparing the experimental data with the theory. The values of the constants obtained are consistent with the data on the inelastic electron-phonon scattering times in the films investigated. The contribution of the transverse phonons is dominant both in the interference correction to the resistivity and in the electron energy relaxation. |
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RPLAB @ phisix @ |
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989 |
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Semenov, A. D.; Nebosis, R. S.; Gousev, Yu. P.; Heusinger, M. A.; Renk, K. F. |
| Title |
Analysis of the nonequilibrium photoresponse of superconducting films to pulsed radiation by use of a two-temperature model |
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Journal Article |
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1995 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
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52 |
Issue |
1 |
Pages |
581-590 |
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HEB, NbN phonon scecific heat, Cp |
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Photoresponse of a superconducting film in the resistive state to pulsed radiation has been studied in the framework of a model assuming that two different effective temperatures can be assigned to the quasiparticle and phonon nonequilibrium distributions. The coupled electron-phonon-substrate system is described by a system of time-dependent energy-balance differential equations for effective temperatures. An analytical solution of the system is given and calculated voltage transients are compared with experimental photoresponse signals taking into account the radiation pulse shape and the time resolution of the readout electronics. It is supposed that a resistive state (vortices, fluxons, network of intergrain junctions, hot spots, phase slip centers) provides an ultrafast connection between electron temperature changes and changes of the film resistance and thus plays a minor role in the temporal evolution of the response. In accordance with experimental observations a two-component response was revealed from simulations. The slower component corresponds to a bolometric mechanism while the fast component is connected with the relaxation of the electron temperature. Calculated photoresponse transients are presented for different ratios of the electron and phonon specific heat, radiation pulse durations and fluences, and frequency band passes of registration electronics. From the amplitude of the bolometric component we determine the radiation energy absorbed in a film. This enables us to reveal an intrinsic electron-phonon scattering time even if it is much shorter than the time resolution of readout electronics. We analyze experimental voltage transients for NbN, YBa2Cu3O7, and TlBa2Ca2Cu3O9 superconducting films and find the electron-phonon interaction times at the transition temperatures of 17, 2.5, and 1.8 ps, respectively. The values are in reasonable agreement with data of other experiments. |
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903 |
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Verevkin, A. I.; Ptitsina, N. G.; Chulkova, G. M.; Gol'tsman, G. N.; Gershenzon, E. M.; Yngvesson, K. S. |
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Electron energy relaxation in a 2D channel in AlGaAs-GaAs heterostructures under quasiequilibrium conditions at low temperatures |
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Journal Article |
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1995 |
Publication |
JETP Lett. |
Abbreviated Journal |
JETP Lett. |
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61 |
Issue |
7 |
Pages |
591-595 |
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2DEG, AlGaAs/GaAs heterostructures |
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The energy relaxation time of 2D electrons, Te, has been measured under quasiequilibrium conditions in AlGaAs—GaAs heterojunctions over the temperature range T= 1.5—20 K. At T> 4 K, Te depends only weakly on the temperature, while at T< 4 K 7;'(T) there is a dependence fr; lNT. A linear dependence 7: 1 (T) in the Bloch—-Grfineisen temperature region (T< 5 K) is unambiguous evidence that a piezoacoustic mechanism of an electron—phonon interaction is predominant in the inelastic scattering of electrons. The values of T6 in this temperature range agree very accurately with theoretical results reported by Karpus [Sov. Phys. Semicond. 22 (1988)]. At higher temperatures, where scat—tering by deformation acoustic phonons becomes substantial, there is a significant discrepancy between the experimental and theoretical re-sults. |
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1624 |
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Zorin, M.; Gol'tsman, G.N.; Karasik, B.S.; Elantev, A.I.; Gershenzon, E.M.; Lindgren, M.; Danerud, M.; Winkler, D. |
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Optical mixing in thin YBa2Cu3O7-x films |
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Journal Article |
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1995 |
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IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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5 |
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2 |
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2431-2434 |
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YBCO HTS HEB mixers |
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High quality, j/sub c/ (77 K)>10/sup 6/ A/cm/sup 2/, epitaxial YBa2Cu3O7-x films of 50 nm thickness were patterned into ten parallel 1 /spl mu/m wide strips. The film structure was coupled to a single-mode fiber. Mixer response was obtained at 0.78 /spl mu/m using laser frequency modulation and an optical delay line. Using two semiconductor lasers at 1.55 /spl mu/m wavelength the beating signal was used to measure the photoresponse up to 18 GHz. Nonequilibrium photoresponse in the resistive state of the superconductor was observed. Bolometric response dominates up to 3 GHz, after which the nonequilibrium response is constant up to the frequency limit of our registration system. Using an electron heating model the influence of different thermal processes on the conversion loss has been analyzed. Ways of increasing the sensitivity are also discussed. |
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1051-8223 |
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1619 |
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Zorin, M.; Lindgren, M.; Danerud, M.; Karasik, B.; Winkler, D.; Gol'tsman, G.; Gershenzon, E. |
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Nonequilibrium and bolometric responses of YBaCuO thin films to high-frequency modulated laser radiation |
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Journal Article |
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1995 |
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J. Supercond. |
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J. Supercond. |
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8 |
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1 |
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11-15 |
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YBCO HTS HEB |
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Picosecond nonequilibrium and slow bolometric responses to infrared radiation from a patterned high-T c superconducting (HTS) film in resistive and normal states deposited onto LaAlO3, NdGaO3, and MgO substrates were investigated using both pulse and modulation techniques. The response time of 35 ps to a laser pulse of 17 ps FWHM has been observed. The intrinsic response time of the fast process is expected to be about a few picoseconds. The modulation technique, being free from the disadvantages of pulse methods (poor sensitivity, limited dynamic range), makes the detailed study of a number of relaxation processes possible. Besides the nonequilibrium response, two kinds of bolometric processes, namely phonon transport through the film-substrate interface and phonon thermal diffusion in a substrate, manifest themselves in certain frequency dependences. |
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1630 |
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Гольцман, Г. Н.; Веревкин, А. А.; Гершензон, Е. М.; Птицина, Н. Г.; Смирнов, К. В.; Чулкова, Г. М. |
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Исследования процессов неупругой релаксации и примесная спектроскопия-релаксометрия в двумерном электронном газе в полупроводниковых структурах с квантовыми ямами |
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1995 |
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В гетероструктурах GaAs/AlGaAs впервые прямым методом измерена температурная зависимость вpемени энеpгетической pелаксации двумерного электронного газа te(T) в широком диапазоне температур Т=1,5 – 50 К в квазиравновесных условиях. Для измерений использовался высокочувствительный спектрометр миллиметрового диапазона волн с высоким временным разрешением, который позволял измерять релаксационные времена до 150 пс с погрешностью не более 20%. Верхний предел температуры определялся временным разрешением спектрометра. Исследования проводились на высококачественных образцах с поверхностной концентрацией носителей ns = 4,2 1011 см-2 и подвижностью m = 7 105 см2В-1с-1 (при Т = 4,2К). В квазиравновесных условиях из температурной зависимости tе определен предел подвижности при низких температурах (T<4.2 K), связанный с рассеянием на пьезоакустическом потенциале, получено время неупругой релаксации, связанное с рассеянием на деформационном потенциале (15 K25 K), получено характерное время испускания оптического фонона (tLO>4,5пс), которое существенно превышает время сронтанного излучения оптического фонона (примерно в 30 раз), что связано с большой ролью процессов перепоглащения фононов электронами.При низких температурах проведены измерения tе в условиях сильного разогрева. Полученные значения tе и зависимость tе от температуры электронов Те совпадают с tе(Т) в квазиравновесных условиях при Т=Те. Из полученных значений tе(Те) построена зависимость мощности энергетических потерь от Те, которая хорошо согласуется с литературными данными.Начаты измерения в магнитном поле, которые показывают переспективность использованного нами метода измерений как в области слабых магнитных полей при факторе заполнения >10, так и в области сильных магнитных полей при факторе заполнения >1-2. |
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Отчет о НИР/НИОКР; РФФИ: 95-02-06409-а; |
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