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| Author |
Bulaevskii, L. N.; Graf, Matthias J.; Kogan, V. G. |
| Title |
Vortex-assisted photon counts and their magnetic field dependence in single-photon superconducting detectors |
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Journal Article |
| Year |
2012 |
Publication |
Phys. Rev. B |
Abbreviated Journal |
Phys. Rev. B |
| Volume |
85 |
Issue |
1 |
Pages |
9 |
| Keywords |
SSPD; SNSPD; single-vortex crossing; normal-state belt |
| Abstract |
We argue that photon counts in a superconducting nanowire single-photon detector (SNSPD) are caused by the transition from a current-biased metastable superconducting state to the normal state. Such a transition is triggered by vortices crossing the thin and narrow superconducting strip from one edge to another due to the Lorentz force. Detector counts in SNSPDs may be caused by three processes: (a) a single incident photon with sufficient energy to break enough Cooper pairs to create a normal-state belt across the entire width of the strip (direct photon count), (b) thermally induced single-vortex crossing in the absence of photons (dark count), which at high-bias currents releases the energy sufficient to trigger the transition to the normal state in a belt across the whole width of the strip, and (c) a single incident photon of insufficient energy to create a normal-state belt but initiating a subsequent single-vortex crossing, which provides the rest of the energy needed to create the normal-state belt (vortex-assisted single-photon count). We derive the current dependence of the rate of vortex-assisted photon counts. The resulting photon count rate has a plateau at high currents close to the critical current and drops as a power law with high exponent at lower currents. While the magnetic field perpendicular to the film plane does not affect the formation of hot spots by photons, it causes the rate of vortex crossings (with or without photons) to increase. We show that by applying a magnetic field one may characterize the energy barrier for vortex crossings and identify the origin of dark counts and vortex-assisted photon counts. |
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RPLAB @ gujma @ |
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733 |
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Boreman, Glenn D. |
| Title |
A Users guide to IR detectors |
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Conference Article |
| Year |
2001 |
Publication |
Proc. SPIE |
Abbreviated Journal |
Proc. SPIE |
| Volume |
4420 |
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Pages |
79-90 |
| Keywords |
optical antennas |
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This paper will guide the first-time user toward proper selection and use of IR detectors for applications in industrial inspection, process control, and laser measurements. |
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RPLAB @ gujma @ |
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735 |
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Hu, Xiaolong; Dauler, Eric A.; Kerman, Andrew J.; Yang, Joel K. W.; White, James E.; Herder, Charles H.; Berggren, Karl K. |
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Using surface plasmons to enhance the speed and efficiency of superconducting nanowire single-photon detectors |
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Conference Article |
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2009 |
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Proceedings of the Conference on Lasers and Electro-Optics, 2009 and 2009 Conference on Quantum electronics and Laser Science Conference |
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Proc of Conf. on Lasers and El.-Opt. |
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1-2 |
| Keywords |
optical antennas |
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We report our design and fabrication of superconducting nanowire single-photon detectors integrated with gold plasmonic nanostructures, which can enhance the absorption of TM-polarized light, and can enlarge the effective area without sacrificing detector speed. |
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RPLAB @ gujma @ |
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744 |
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| Author |
Novotny, Lukas |
| Title |
Effective wavelength scaling for optical antennas |
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Journal Article |
| Year |
2007 |
Publication |
Phys. Rev. Lett. |
Abbreviated Journal |
Phys. Rev. Lett. |
| Volume |
98 |
Issue |
26 |
Pages |
266802(1-4) |
| Keywords |
optical antennas |
| Abstract |
In antenna theory, antenna parameters are directly related to the wavelength λ of incident radiation, but this scaling fails at optical frequencies where metals behave as strongly coupled plasmas. In this Letter we show that antenna designs can be transferred to the optical frequency regime by replacing λ by a linearly scaled effective wavelength λeff=n1+n2λ/λp, with λp being the plasma wavelength and n1, n2 being coefficients that depend on geometry and material properties. It is assumed that the antenna is made of linear segments with radii Râ‰<aa>λ. Optical antennas hold great promise for increasing the efficiency of photovoltaics, light-emitting devices, and optical sensors. |
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RPLAB @ gujma @ |
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749 |
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| Author |
Puscasu, Irina; Boreman, Glenn D. |
| Title |
Theoretical and experimental analysis of transmission and enchanced absorption of frequency selective surfaces in the infrared |
Type |
Conference Article |
| Year |
2001 |
Publication |
Proc. SPIE |
Abbreviated Journal |
Proc. SPIE |
| Volume |
4293 |
Issue |
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Pages |
185-190 |
| Keywords |
optical antennas |
| Abstract |
A comparative study between theory and experiment is presented for transmission through lossy frequency selective surfaces (FSSs) on silicon in the 2 – 15 micrometer range. Important parameters controlling the resonance shape and location are identified: dipole length, spacing, impedance, and dielectric surroundings. Their separate influence is exhibited. The primary resonance mechanism of FSSs is the resonance of the individual metallic patches. There is no discernable resonance arising from a feed-coupled configuration. The real part of the element's impedance controls the minimum value of transmission, while scarcely affecting its location. Varying the imaginary part shifts the location of resonance, while only slightly changing the minimum value of transmission. With such fine-tuning, it is possible to make a good fit between theory and experiment near the dipole resonance on any sample. A fixed choice of impedance can provide a reasonable fit to all samples fabricated under the same conditions. The dielectric surroundings change the resonance wavelength of the FSS compared to its value in air. The presence of FSS on the substrate increases the absorptivity/emissivity of the surface in a resonant way. Such enhancement is shown for dipole and cross arrays at several wavelengths. |
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RPLAB @ gujma @ |
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753 |
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