Records |
Author |
Danerud, M.; Winkler, D.; Lindgren, M.; Zorin, M.; Trifonov, V.; Karasik, B. S.; Gol’tsman, G. N.; Gershenzon, E. M. |
Title |
Nonequilibrium and bolometric photoresponse in patterned YBa2Cu3O7−δ thin films |
Type |
Journal Article |
Year |
1994 |
Publication |
J. Appl. Phys. |
Abbreviated Journal |
J. Appl. Phys. |
Volume |
76 |
Issue |
3 |
Pages |
1902-1909 |
Keywords |
YBCO HTS HEB detector, nonequilibrium response |
Abstract |
Epitaxial laser deposited YBa2Cu3O7−δ films of ∼50 nm thickness were patterned into detectors consisting of ten parallel 1 μm wide strips in order to study nonequilibrium and bolometric effects. Typically, the patterned samples had critical temperatures around 86 K, transition widths around 2 K and critical current densities above 1×106A/cm2 at 77 K. Pulsed laser measurements at 0.8 μm wavelength (17 ps full width at half maximum) showed a ∼30 ps response, attributed to electron heating, followed by a slower bolometric decay. Amplitude modulation in the band fmod=100 kHz–10 GHz of a laser with wavelength λ=0.8 μm showed two different thermal relaxations in the photoresponse. Phonon escape from the film (∼3 ns) is the limiting process, followed by heat diffusion in the substrate. Similar relaxations were also seen for λ=10.6 μm. The photoresponse measurements were made with the film in the resistive state and extended into the normal state. These states were created by supercritical bias currents. Measurements between 75 and 95 K (i.e., from below to above Tc) showed that the photoresponse was proportional to dR/dT for fmod=1 MHz and 4 GHz. The fast response is limited by the electron‐phonon scattering time, estimated to 1.8 ps from experimental data. The responsivity both at 0.8 and 10.6 μm wavelength was ∼1.2 V/W at fmod=1 GHz and the noise equivalent power was calculated to 1.5×10−9 WHz−1/2 for the fast response. |
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0021-8979 |
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1637 |
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Gol'tsman, G. N.; Kouminov, P.; Goghidze, I.; Gershenzon, E. M. |
Title |
Nonequilibrium kinetic inductive response of YBaCuO thin films to low-power laser pulses |
Type |
Journal Article |
Year |
1994 |
Publication |
Phys. C: Supercond. |
Abbreviated Journal |
Phys. C: Supercond. |
Volume |
235-240 |
Issue |
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Pages |
1979-1980 |
Keywords |
YBCO HTS KID |
Abstract |
Transient non-equilibrium kinetic inductive voltage response of YBaCuO thin films to 20 ps pulses of YAG:Nd laser radiation with 0.63 μm and 1.5 μm wavelength has been revealed. By increasing the sensitivity of 100 ps resolution time registration system and diminishing light intensity (fluence 0.1-1 μJ2/cm2) and transport current (density j≤105 A/cm2) we observed a perculiar bipolar signal form with nearly equal amplitudes of 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: nonequilibrium picosecond scale component followed by bolometric nanosecond. Nonequilibrium response is interpreted as suppression of order parameter by excess of quasiparticles followed by a change in resistance in the resistive state and kinetic inductance in superconductive state. |
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0921-4534 |
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1634 |
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Semenov, A. D.; Goghidze, I. G.; Gol’tsman, G. N.; Sergeev, A. V.; Aksaev, E. E.; Gershenzon, E. M. |
Title |
Non-equilibrium quasiparticle response to radiation and bolometric effect in YBaCuO films |
Type |
Journal Article |
Year |
1993 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
Volume |
3 |
Issue |
1 |
Pages |
2132-2135 |
Keywords |
YBCO HTS HEB detectors |
Abstract |
The voltage photoresponse of structured current biased YBCO films on different substrates to 20-ps laser pulses of 0.63- mu m and 1.54- mu m wavelengths and to continuously modulated radiation of 2-mm wavelength is measured to temperatures around Tc. Fast picosecond decay of the response to pulsed radiation is followed by slow exponential relaxation with a nanosecond characteristic time depending on the substrate material and film dimensions. The slow component does not depend on wavelength and is attributed to the bolometric effect, while the magnitude of the fast component associated with nonequilibrium response rises with wavelength. More than an order-of-magnitude increase of the nonequilibrium response is seen from near-infrared to millimeter-wave range. This dependence plausibly reflects the low efficiency of multiplication of photoexcited electrons in YBaCuO compared to conventional superconductors. |
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1558-2515 |
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1659 |
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Nebosis, R. S.; Heusinger, M. A.; Schatz, W.; Renk, K. F.; Gol’tsman, G. N.; Karasik, B. S.; Semenov, A. D.; Gershenzon, E. M. |
Title |
Ultrafast photoresponse of a structured YBa2Cu3O7-δ thin film to ultrashort FIR laser pulses |
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Journal Article |
Year |
1993 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
Volume |
3 |
Issue |
1 |
Pages |
2160-2162 |
Keywords |
YBCO HTS detectors |
Abstract |
The authors have investigated the photoinduced voltage response of a current-carrying structured YBa2Cu3O7-δ thin film to ultrashort far-infrared (FIR) laser pulses in the frequency range from 0.7 THz to 7 THz. The detector has shown an almost constant sensitivity of 1 mV/W and a noise equivalent power of less than 5*10/sup -7/ W/ square root Hz. The temperature dependence of the decay time of the detector signal was studied for temperatures around the transition temperature of the film ( approximately 80 K). For a detector temperature where dR/dT had its maximum, the authors observed bolometric signals with decay times of about 2 ns, and for lower temperatures they observed nonbolometric signals with decay times of approximately 120 ps; the duration of the nonbolometric signals was limited by the time resolution of the electronic registration equipment. |
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1658 |
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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 |
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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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