| Home | << 1 2 3 4 5 6 7 >> |
|
| Records | |||||
|---|---|---|---|---|---|
| Author | Kerman, A. J.; Dauler, E. A.; Yang, J. K. W.; Rosfjord, K. M.; Anant, V.; Berggren, K. K.; Gol’tsman, G. N.; Voronov, B. M. | ||||
| Title | Constriction-limited detection efficiency of superconducting nanowire single-photon detectors | Type | Journal Article | ||
| Year | 2007 | Publication | Appl. Phys. Lett. | Abbreviated Journal | Appl. Phys. Lett. |
| Volume | 90 | Issue | 10 | Pages | 101110 (1 to 3) |
| Keywords | SSPD, SNSPD | ||||
Abstract  |
We investigate the source of the large variations in the observed detection efficiencies of superconducting nanowire single-photon detectors between many nominally identical devices. Through both electrical and optical measurements, we infer that these variations arise from “constrictions:” highly localized regions of the nanowires where the effective cross-sectional area for superconducting current is reduced. These constrictions limit the bias-current density to well below its critical value over the remainder of the wire, and thus prevent the detection efficiency from reaching the high values that occur in these devices when they are biased near the critical current density. This work is sponsored by the United States Air Force under Contract No. FA8721-05-C-0002. |
||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 0003-6951 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | no | |||
| Call Number | Serial | 1433 | |||
| Permanent link to this record | |||||
| Author | Bell, M.; Sergeev, A.; Mitin, V.; Bird, J.; Verevkin, A.; Gol’tsman, G. | ||||
| Title | One-dimensional resistive states in quasi-two-dimensional superconductors: Experiment and theory | Type | Journal Article | ||
| Year | 2007 | Publication | Phys. Rev. B | Abbreviated Journal | Phys. Rev. B |
| Volume | 76 | Issue | 9 | Pages | 094521 (1 to 5) |
| Keywords | uasi-two-dimensional superconductors, NbN | ||||
| Abstract |
We investigate competition between one- and two-dimensional topological excitations—phase slips and vortices—in the formation of resistive states in quasi-two-dimensional superconductors in a wide temperature range below the mean-field transition temperature TC0. The widths w=100nm of our ultrathin NbN samples are substantially larger than the Ginzburg-Landau coherence length ξ=4nm, and the fluctuation resistivity above TC0 has a two-dimensional character. However, our data show that the resistivity below TC0 is produced by one-dimensional excitations—thermally activated phase slip strips (PSSs) overlapping the sample cross section. We also determine the scaling phase diagram, which shows that even in wider samples the PSS contribution dominates over vortices in a substantial region of current and/or temperature variations. Measuring the resistivity within 7 orders of magnitude, we find that the quantum phase slips can only be essential below this level. | ||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 1098-0121 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | no | |||
| Call Number | Serial | 1423 | |||
| Permanent link to this record | |||||
| Author | Bell, M.; Sergeev, A.; Mitin, V.; Bird, J.; Verevkin, A.; Gol'tsman, G. | ||||
| Title | One-dimensional resistive states in quasi-two-dimensional superconductors | Type | Journal Article | ||
| Year | 2007 | Publication | arXiv:0709.0709v1 [cond-mat.supr-con] | Abbreviated Journal | |
| Volume | Issue | Pages | 1-11 | ||
| Keywords | |||||
| Abstract |
We investigate competition between one- and two-dimensional topological excitations – phase slips and vortices – in formation of resistive states in quasi-two-dimensional superconductors in a wide temperature range below the mean-field transition temperature T(C0). The widths w = 100 nm of our ultrathin NbN samples is substantially larger than the Ginzburg-Landau coherence length ξ = 4nm and the fluctuation resistivity above T(C0) has a two-dimensional character. However, our data shows that the resistivity below T(C0) is produced by one-dimensional excitations, – thermally activated phase slip strips (PSSs) overlapping the sample cross-section. We also determine the scaling phase diagram, which shows that even in wider samples the PSS contribution dominates over vortices in a substantial region of current/temperature variations. Measuring the resistivity within seven orders of magnitude, we find that the quantum phase slips can only be essential below this level. | ||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | ISBN | Medium | |||
| Area | Expedition | Conference | |||
| Notes | Approved | no | |||
| Call Number | RPLAB @ atomics90 @ | Serial | 948 | ||
| Permanent link to this record | |||||
| Author | Gao, J. R.; Hajenius, M.; Yang, Z. Q.; Baselmans, J. J. A.; Khosropanah, P.; Barends, R.; Klapwijk, T. M. | ||||
| Title | Terahertz superconducting hot electron bolometer heterodyne receivers | Type | Journal Article | ||
| Year | 2007 | Publication | IEEE Trans. Appl. Supercond. | Abbreviated Journal | |
| Volume | 17 | Issue | 2 | Pages | 252-258 |
| Keywords | HEB, mixer, direct detection effect | ||||
| Abstract |
We highlight the progress on NbN hot electron bolometer (HEB) mixers achieved through fruitful collaboration between SRON Netherlands Institute for Space Research and Delft University of Technology, the Netherlands. This includes the best receiver noise temperatures of 700 K at 1.63 THz using a twin-slot antenna mixer and 1050 K at 2.84 THz using a spiral antenna coupled HEB mixer. The mixers are based on thin NbN films on Si and fabricated with a new contact-process and-structure. By reducing their areas HEB mixers have shown an LO power requirement as low as 30 nW. Those small HEB mixers have demonstrated equivalent sensitivity as those with large areas provided the direct detection effect due to broadband radiation is removed. To manifest that a HEB based heterodyne receiver can in practice be used at arbitrary frequencies above 2 THz, we demonstrate a 2.8 THz receiver using a THz quantum cascade laser (QCL) as local oscillator. | ||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 1051-8223 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | no | |||
| Call Number | RPLAB @ asmirn @ | Serial | 557 | ||
| Permanent link to this record | |||||
| Author | Khosropanah, P.; Gao, J. R.; Laauwen, W. M.; Hajenius, M; Klapwijk, T. M. | ||||
| Title | Low noise NbN hot electron bolometer mixer at 4.3 THz | Type | Journal Article | ||
| Year | 2007 | Publication | Appl. Phys. Lett. | Abbreviated Journal | Appl. Phys. Lett. |
| Volume | 91 | Issue | Pages | 221111 (1 to 3) | |
| Keywords | NbN HEB mixers, NbN, contacts cleaning | ||||
| Abstract |
We have studied the sensitivity of a superconducting NbN hot electron bolometer mixer integrated with a spiral antenna at 4.3 THz. Using hot/cold blackbody loads and a beam splitter all in vacuum, we measured a double sideband receiver noise temperature of 1300 K at the optimum local oscillator (LO) power of 330 nW, which is about 12 times the quantum noise (hnu/2kB). Our result indicates that there is no sign of degradation of the mixing process at the superterahertz frequencies. Moreover, a measurement method is introduced which allows us for an accurate determination of the sensitivity despite LO power fluctuations. | ||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | ISBN | Medium | |||
| Area | Expedition | Conference | |||
| Notes | Approved | no | |||
| Call Number | Serial | 584 | |||
| Permanent link to this record | |||||
| Author | Ejrnaes, M.; Cristiano, R.; Quaranta, O.; Pagano, S.; Gaggero, A.; Mattioli, F.; Leoni, R.; Voronov, B.; Gol’tsman, G. | ||||
| Title | A cascade switching superconducting single photon detector | Type | Journal Article | ||
| Year | 2007 | Publication | Appl. Phys. Lett. | Abbreviated Journal | Appl. Phys. Lett. |
| Volume | 91 | Issue | 26 | Pages | 262509 (1 to 3) |
| Keywords | SSPD, SNSPD, parallel-wire | ||||
| Abstract |
We have realized superconducting single photon detectors with reduced inductance and increased signal pulse amplitude. The detectors are based on a parallel connection of ultrathin NbN nanowires with a common bias inductance. When properly biased, an absorbed photon induces a cascade switch of all the parallel wires generating a signal pulse amplitude of 2mV. The parallel wire configuration lowers the detector inductance and reduces the response time well below 1ns. This work was performed in the framework of the EU project “SINPHONIA” NMP4-CT-2005-016433. |
||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 0003-6951 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | no | |||
| Call Number | Serial | 1418 | |||
| Permanent link to this record | |||||
| Author | Kitaygorsky, Jennifer; Komissarov, I.; Jukna, A.; Minaeva, O.; Kaurova, N.; Divochiy, A.; Korneev, A.; Tarkhov, M.; Voronov, B.; Milostnaya, I.; Gol'tsman, G.; Sobolewski, R. | ||||
| Title | Fluctuations in two-dimensional superconducting NbN nanobridges and nanostructures meanders | Type | Abstract | ||
| Year | 2007 | Publication | Proc. APS March Meeting | Abbreviated Journal | Proc. APS March Meeting |
| Volume | 52 | Issue | 1 | Pages | L9.00013 |
| Keywords | |||||
| Abstract |
We have observed fluctuations, manifested as sub-nanosecond to nanosecond transient, millivolt-amplitude voltage pulses, generated in two-dimensional NbN nanobridges, as well as in extended superconducting meander nanostructures, designed for single photon counting. Both nanobridges and nano-stripe meanders were biased at currents close to the critical current and measured in a range of temperatures from 1.5 to 8 K. During the tests, the devices were blocked from all incoming radiation by a metallic enclosure and shielded from any external magnetic fields. We attribute the observed spontaneous voltage pulses to the Kosterlitz-Thouless-type fluctuations, where the high enough applied bias current reduces the binding energy of vortex-antivortex pairs and, subsequently, thermal fluctuations break them apart causing the order parameter to momentarily reduce to zero, which in turn causes a transient voltage pulse. The duration of the voltage pulses depended on the device geometry (with the high-kinetic inductance meander structures having longer, nanosecond, pulses) while their rate was directly related to the biasing current as well as temperature. | ||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | ISBN | Medium | |||
| Area | Expedition | Conference | |||
| Notes | Approved | no | |||
| Call Number | Serial | 1027 | |||
| Permanent link to this record | |||||
| Author | Ryabchun, S.; Tong, C.-Y. E.; Blundell, R.; Kimberk, R.; Gol'tsman, G. | ||||
| Title | Study of the effect of microwave radiation on the operation of HEB mixers in the terahertz frequency range | Type | Journal Article | ||
| Year | 2007 | Publication | IEEE Trans. Appl. Supercond. | Abbreviated Journal | IEEE Trans. Appl. Supercond. |
| Volume | 17 | Issue | 2 | Pages | 391-394 |
| Keywords | NbN HEB mixers | ||||
| Abstract |
We have investigated the effect of injecting microwave radiation, with a frequency much lower than that corresponding to the energy gap of the superconductor, on the performance of the hot-electron bolometer mixer incorporated into a THz heterodyne receiver. More specifically, we show that exposing the mixer to microwave radiation does not cause a significant rise of the receiver noise temperature and fall of the mixer conversion gain so long as the microwave power is a small fraction of local oscillator power. The injection of a small, but controlled amount of microwave power therefore enables active compensation of local oscillator power and coupling fluctuations which can significantly degrade the gain stability of hot electron bolometer mixer receivers. | ||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | 1051-8223 | ISBN | Medium | ||
| Area | Expedition | Conference | |||
| Notes | Approved | no | |||
| Call Number | Serial | 1427 | |||
| Permanent link to this record | |||||
| Author | Slysz, W.; Wegrzecki, M.; Bar, J.; Grabiec, P.; Gorska, M.; Rieger, E.; Dorenbos, P.; Zwiller, V.; Milostnaya, I.; Minaeva, O.; Antipov, A.; Okunev, O.; Korneev, A.; Smirnov, K.; Voronov, B.; Kaurova, N.; Gol’tsman, G.N.; Kitaygorsky, J.; Pan, D.; Pearlman, A.; Cross, A.; Komissarov, I.; Sobolewski, R. | ||||
| Title | Fiber-coupled NbN superconducting single-photon detectors for quantum correlation measurements | Type | Conference Article | ||
| Year | 2007 | Publication | Proc. SPIE | Abbreviated Journal | Proc. SPIE |
| Volume | 6583 | Issue | Pages | 65830J (1 to 11) | |
| Keywords | NbN SSPD, SNSPD, superconducting single-photon detectors, single-photon detectors, fiber-coupled optical detectors, quantum correlations, superconducting devices | ||||
| Abstract |
We have fabricated fiber-coupled superconducting single-photon detectors (SSPDs), designed for quantum-correlationtype experiments. The SSPDs are nanostructured ( 100-nm wide and 4-nm thick) NbN superconducting meandering stripes, operated in the 2 to 4.2 K temperature range, and known for ultrafast and efficient detection of visible to nearinfrared photons with almost negligible dark counts. Our latest devices are pigtailed structures with coupling between the SSPD structure and a single-mode optical fiber achieved using a micromechanical photoresist ring placed directly over the meander. The above arrangement withstands repetitive thermal cycling between liquid helium and room temperature, and we can reach the coupling efficiency of up to 33%. The system quantum efficiency, measured as the ratio of the photons counted by SSPD to the total number of photons coupled into the fiber, in our early devices was found to be around 0.3 % and 1% for 1.55 &mgr;m and 0.9 &mgr;m photon wavelengths, respectively. The photon counting rate exceeded 250 MHz. The receiver with two SSPDs, each individually biased, was placed inside a transport, 60-liter liquid helium Dewar, assuring uninterrupted operation for over 2 months. Since the receiver’s optical and electrical connections are at room temperature, the set-up is suitable for any applications, where single-photon counting capability and fast count rates are desired. In our case, it was implemented for photon correlation experiments. The receiver response time, measured as a second-order photon cross-correlation function, was found to be below 400 ps, with timing jitter of less than 40 ps. | ||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Spie | Place of Publication | Editor | Dusek, M.; Hillery, M.S.; Schleich, W.P.; Prochazka, I.; Migdall, A.L.; Pauchard, A. | |
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | ISBN | Medium | |||
| Area | Expedition | Conference | Photon Counting Applications, Quantum Optics, and Quantum Cryptography | ||
| Notes | Approved | no | |||
| Call Number | Serial | 1431 | |||
| Permanent link to this record | |||||
| Author | Koch, Martin | ||||
| Title | Terahertz communications: a 2020 vision | Type | Book Chapter | ||
| Year | 2007 | Publication | NATO Security through Science Series | Abbreviated Journal | |
| Volume | 2007 | Issue | Pages | 325-338 | |
| Keywords | terahertz THz communications | ||||
| Abstract |
We discuss basic considerations for potential short-range THz communication systems which may replace or supplement present WLAN systems in 10–15 years from now. On the basis of a few fundamental estimations we show that such a system will need a line-of-sight connection between receiver and emitter. To circumvent the blocking of the direct line-of-sight connection indoor THz communication systems will also have to rely on non-line-of-sight paths which involve reflections off the walls. The reflectivity of the walls can be enhanced by dielectric mirrors. This new scheme makes steerable high-gain antennas a necessity. Hence, a wireless THz communication system can not be a simple extension of the existing technology of today's local area networks. Instead it involves completely new concepts and ideas that have not yet been worked upon. | ||||
| Address | |||||
| Corporate Author | Thesis | ||||
| Publisher | Place of Publication | Editor | |||
| Language | Summary Language | Original Title | |||
| Series Editor | Series Title | Abbreviated Series Title | |||
| Series Volume | Series Issue | Edition | |||
| ISSN | ISBN | Medium | |||
| Area | Expedition | Conference | |||
| Notes | Approved | no | |||
| Call Number | Serial | 594 | |||
| Permanent link to this record | |||||