| Records |
| Author |
Gousev, Yu. P.; Gol'tsman, G. N.; Semenov, A. D.; Gershenzon, E. M.; Nebosis, R. S.; Heusinger, M. A.; Renk, K. F. |
| Title |
Broadband ultrafast superconducting NbN detector for electromagnetic radiation |
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Journal Article |
| Year |
1994 |
Publication |
J. Appl. Phys. |
Abbreviated Journal |
J. Appl. Phys. |
| Volume |
75 |
Issue |
7 |
Pages |
3695-3697 |
| Keywords |
NbN HEB |
| Abstract |
An ultrafast detector that is sensitive to radiation in a broad spectral range from submillimeter waves to visible light is reported. It consists of a structured NbN thin film cooled to a temperature below Tc (∼11 K). Using 20 ps pulses of a GaAs laser, we observed signal pulses with both rise and decay time of about 50 ps. From the analysis of a mixing experiment with submillimeter radiation we estimate an intrinsic response time of the detector of ∼12 ps. The sensitivity was found to be similar for the near‐infrared and submillimeter radiation. Broadband sensitivity and short response time are attributed to a quasiparticle heating effect. |
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252 |
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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 |
Type |
Journal Article |
| Year |
1995 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
| Volume |
52 |
Issue |
1 |
Pages |
581-590 |
| Keywords |
HEB, NbN phonon scecific heat, Cp |
| Abstract |
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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Gousev, Y. P.; Semenov, A. D.; Goghidze, I. G.; Pechen, E. V.; Varlashkin, A. V.; Gol'tsman, G. N.; Gershenzon, E. M.; Renk, K. F. |
| Title |
Current dependent noise in a YBa2Cu3O7-δ hot-electron bolometer |
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Journal Article |
| Year |
1997 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
| Volume |
7 |
Issue |
2 |
Pages |
3556-3559 |
| Keywords |
YBCO HTS HEB mixers |
| Abstract |
We investigated the output noise of a YBa2Cu3O7-δ (YBCO) superconducting hot-electron bolometer (HEB) in a large frequency range (10 kHz to 8 GHz); the bolometer either consisted of a structured 50 nm thick YBCO film on LaAlO/sub 3/ or a 30 nm thick film on a MgO substrate. We found that flicker noise dominated at low frequencies (below 1 MHz), while at higher frequencies Johnson noise and a current dependent noise were the main noise sources. |
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1051-8223 |
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1592 |
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Semenov, A. D.; Gousev, Y. P.; Renk, K. F.; Voronov, B. M.; Gol'tsman, G. N.; Gershenzon, E. M.; Schwaab, G.W.; Feinaugle, R. |
| Title |
Noise characteristics of a NbN hot-electron mixer at 2.5 THz |
Type |
Journal Article |
| Year |
1997 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
| Volume |
7 |
Issue |
2 |
Pages |
3572-3575 |
| Keywords |
NbN HEB mixers |
| Abstract |
The noise temperature of a NbN phonon cooled hot-electron mixer has been measured at a frequency of 2.5 THz for various operating conditions. We obtained for optimal operation a double sideband mixer noise temperature of /spl ap/14000 K and a system conversion loss of /spl ap/23 dB at intermediate frequencies up to 1 GHz. The dependences of the mixer noise temperature on the bias voltage, local oscillator power, and intermediate frequency were consistent with the phenomenological description based on the effective temperature approximation. |
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1051-8223 |
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1594 |
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Svechnikov, S.; Gol'tsman, G.; Voronov, B.; Yagoubov, P.; Cherednichenko, S.; Gershenzon, E.; Belitsky, V.; Ekstrom, H.; Kollberg, E.; Semenov, A.; Gousev, Y.; Renk, K. |
| Title |
Spiral antenna NbN hot-electron bolometer mixer at submm frequencies |
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Journal Article |
| Year |
1997 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
| Volume |
7 |
Issue |
2 |
Pages |
3395-3398 |
| Keywords |
NbN HEB mixers |
| Abstract |
We have studied the phonon-cooled hot-electron bolometer (HEB) as a quasioptical mixer based on a spiral antenna designed for the 0.3-1 THz frequency band and fabricated on sapphire and high resistivity silicon substrates. HEB devices were produced from superconducting 3.5-5 nm thick NbN films with a critical temperature 10-12 K and a critical current density of approximately 10/sup 7/ A/cm/sup 2/ at 4.2 K. For these devices we reached a DSB receiver noise temperature below 1500 K, a total conversion loss of L/sub t/=16 dB in the 500-700 GHz frequency range, an IF bandwidth of 3-4 GHz and an optimal LO absorbed power of /spl sime/4 /spl mu/W. We experimentally analyzed various contributions to the conversion loss and obtained an RF coupling factor of about 5 dB, internal mixer loss of 10 dB and IF mismatch of 1 dB. |
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1051-8223 |
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1597 |
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