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Il’in, K. S.; Milostnaya, I. I.; Verevkin, A. A.; Gol’tsman, G. N.; Gershenzon, E. M.; Sobolewski, R. |
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Title |
Ultimate quantum efficiency of a superconducting hot-electron photodetector |
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Journal Article |
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1998 |
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Appl. Phys. Lett. |
Abbreviated Journal |
Appl. Phys. Lett. |
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Volume |
73 |
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26 |
Pages |
3938-3940 |
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Keywords |
NbN SSPD, SNSPD |
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Abstract |
The quantum efficiency and current and voltage responsivities of fast hot-electron photodetectors, fabricated from superconducting NbN thin films and biased in the resistive state, have been shown to reach values of 340, 220 A/W, and 4×104 V/W,
respectively, for infrared radiation with a wavelength of 0.79 μm. The characteristics of the photodetectors are presented within the general model, based on relaxation processes in the nonequilibrium electron heating of a superconducting thin film. The observed, very high efficiency and sensitivity of the superconductor absorbing the photon are explained by the high multiplication rate of quasiparticles during the avalanche breaking of Cooper pairs. |
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0003-6951 |
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1579 |
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Lindgren, M.; Currie, M.; Zeng, W.-S.; Sobolewski, R.; Cherednichenko, S.; Voronov, B.; Gol'tsman, G. N. |
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Title |
Picosecond response of a superconducting hot-electron NbN photodetector |
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Journal Article |
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1998 |
Publication |
Appl. Supercond. |
Abbreviated Journal |
Appl. Supercond. |
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6 |
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7-9 |
Pages |
423-428 |
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NbN SSPD, SNSPD |
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The ps optical response of ultrathin NbN photodetectors has been studied by electro-optic sampling. The detectors were fabricated by patterning ultrathin (3.5 nm thick) NbN films deposited on sapphire by reactive magnetron sputtering into either a 5×10 μm2 microbridge or 25 1 μm wide, 5 μm long strips connected in parallel. Both structures were placed at the center of a 4 mm long coplanar waveguide covered with Ti/Au. The photoresponse was studied at temperatures ranging from 2.15 K to 10 K, with the samples biased in the resistive (switched) state and illuminated with 100 fs wide laser pulses at 395 nm wavelength. At T=2.15 K, we obtained an approximately 100 ps wide transient, which corresponds to a NbN detector response time of 45 ps. The photoresponse can be attributed to the nonequilibrium electron heating effect, where the incident radiation increases the temperature of the electron subsystem, while the phonons act as the heat sink. The high-speed response of NbN devices makes them an excellent choice for an optoelectronic interface for superconducting digital circuits, as well as mixers for the terahertz regime. The multiple-strip detector showed a linear dependence on input optical power and a responsivity =3.9 V/W. |
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0964-1807 |
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1584 |
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Il'in, K. S.; Verevkin, A. A.; Gol'tsman, G. N.; Sobolewski, R. |
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Title |
Infrared hot-electron NbN superconducting photodetectors for imaging applications |
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1999 |
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Supercond. Sci. Technol. |
Abbreviated Journal |
Supercond. Sci. Technol. |
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12 |
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11 |
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755-758 |
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NbN SSPD, SNSPD |
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We report an effective quantum efficiency of 340, responsivity >200 A W-1 (>104 V W-1) and response time of 27±5 ps at temperatures close to the superconducting transition for NbN superconducting hot-electron photodetectors (HEPs) in the near-infrared and optical ranges. Our studies were performed on a few nm thick NbN films deposited on sapphire substrates and patterned into µm-size multibridge detector structures, incorporated into a coplanar transmission line. The time-resolved photoresponse was studied by means of subpicosecond electro-optic sampling with 100 fs wide laser pulses. The quantum efficiency and responsivity studies of our photodetectors were conducted using an amplitude-modulated infrared beam, fibre-optically coupled to the device. The observed picosecond response time and the very high efficiency and sensitivity of the NbN HEPs make them an excellent choice for infrared imaging photodetectors and input optical-to-electrical transducers for superconducting digital circuits. |
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0953-2048 |
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1562 |
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Author |
Il'in, K. S.; Currie, M.; Lindgren, M.; Milostnaya, I. I.; Verevkin, A. A.; Gol'tsman, G. N.; Sobolewski, R. |
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Title |
Quantum efficiency and time-domain response of superconducting NbN hot-electron photodetectors |
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Year |
1999 |
Publication |
IEEE Trans. Appl. Supercond. |
Abbreviated Journal |
IEEE Trans. Appl. Supercond. |
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Volume |
9 |
Issue |
2 |
Pages |
3338-3341 |
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Keywords |
NbN SSPD, SNSPD |
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We report our studies on the response of ultrathin superconducting NbN hot-electron photodetectors. We have measured the photoresponse of few-nm-thick, micron-size structures, which consisted of single and multiple microbridges, to radiation from the continuous-wave semiconductor laser and the femtosecond Ti:sapphire laser with the wavelength of 790 nm and 400 nm, respectively. The maximum responsivity was observed near the film's superconducting transition with the device optimally current-biased in the resistive state. The responsivity of the detector, normalized to its illuminated area and the coupling factor, was 220 A/W(3/spl times/10/sup 4/ V/W), which corresponded to a quantum efficiency of 340. The responsivity was wavelength independent from the far infrared to the ultraviolet range, and was at least two orders of magnitude higher than comparable semiconductor optical detectors. The time constant of the photoresponse signal was 45 ps, when was measured at 2.15 K in the resistive (switched) state using a cryogenic electro-optical sampling technique with subpicosecond resolution. The obtained results agree very well with our calculations performed using a two-temperature model of the electron heating in thin superconducting films. |
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1051-8223 |
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1566 |
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Verevkin, A.; Williams, C.; Gol’tsman, G. N.; Sobolewski, R.; Gilbert, G. |
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Title |
Single-photon superconducting detectors for practical high-speed quantum cryptography |
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Miscellaneous |
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2001 |
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OFCC/ICQI |
Abbreviated Journal |
OFCC/ICQI |
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Pa3 |
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NbN SSPD, SNSPD, QKD, quantum cryptography |
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We have developed an ultrafast superconducting single-photon detector with negligible dark counting rate. The detector is based on an ultrathin, submicron-wide NbN meander-type stripe and can detect individual photons in the visible to near-infrared wavelength range at a rate of at least 10 Gb/s. The above counting rate allows us to implement the NbN device to unconditionally secret quantum key distRochester, New Yorkribution in a practical, high-speed system using real-time Vernam enciphering. |
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Rochester, New York |
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Optical Society of America |
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Optical Fiber Communication Conference and International Conference on Quantum Information |
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-- from poster session. |
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1544 |
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