Single-Photon Detection with Ultranarrow Superconducting Nanowires
- Category: Electronic Devices, Materials, Nanotechnology, Optics & Photonics
- Tags: Faraz Najafi, Francesco Marsili, Karl Berggren
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Download as PDFSuperconducting nanowire single-photon detectors (SNSPDs) [1] perform single-photon counting in the near‑infrared with outstanding performance. The main limitations of standard SNSPDs, based on ~ 4-nm-thick, 100-nm-wide NbN nanowires, are: (1) fragility with respect to constrictions; and (2) substantially reduced sensitivity beyond 2 µm wavelength (λ). We developed SNSPDs based on ultra-narrow (30- to 10-nm-wide) superconducting nanowires [2] , which showed improved robustness to constrictions and higher sensitivity to near-infrared photons with respect to standard SNSPDs.
As shown in Figure 1, at λ = 1550 nm our 30 nm nanowire‑width SNSPDs could be biased far from the device critical current (IC) with minimal loss in detection efficiency (η), so even heavily‑constricted devices could reach the same efficiency as constriction‑free ones.
As shown in Figure 2 a, varying λ from 700 to 2100 nm, the η vs bias current (IB) curves of 30 nm nanowire‑width SNSPDs kept a sigmoidal shape, with the cut-off current (Ico, taken to be at the inflection point of the η vs IB curves) increasing from 0.31 IC to 0.41 IC. For 90 nm nanowire‑width detectors (shown in Figure 2 b), Ico increased from 0.64 IC at λ = 500 nm to 0.89 IC at λ = 1400 nm. This behavior indicates that ultra-narrow-nanowire SNSPDs are more sensitive to low-energy photons than standard devices and suggests that their sensitivity may extend to mid-infrared wavelengths.
The MIT Lincoln Laboratory portion was sponsored by the Department of the Air Force under Air Force Contract #FA8721-05-C-0002. Opinions, interpretations, recommendations and conclusions are those of the authors and are not necessarily endorsed by the United States Government.
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- Figure 1: η as a function of the normalized bias current (IB / IC) for a constricted SNSPD (red curve) and a constriction-free SNSPD (blue curve) based on 30 nm wide nanowires. Inset: Scanning electron microscope image of an SNSPD hydrogen silsesquioxane mask on NbN. The nanowires are 30 nm wide and the pitch is 100 nm.
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- Figure 2: a. η vs IB / IC curves of a 30 nm nanowire width SNSPD for λ varying from 700 nm (purple curve) to 2100 nm (black curve). The detection efficiency curves at each wavelength were normalized by the value of η at the switching current (ISW). b. η vs IB / IC curves of a 90 nm nanowire width SNSPD for λ varying from 700 nm (purple curve) to 2100 nm (black curve).
- G. N. Gol’tsman, O. Okunev, G. Chulkova, A. Lipatov, A. Semenov, K. Smirnov, B. Voronov, A. Dzardanov, C. Williams, and R. Sobolewski, “Picosecond superconducting single-photon optical detector,” Applied Physics Letters, vol. 79, no. 6, pp. 705-707, 2001. [↩]
- F. Marsili, F. Najafi, E. Dauler, X. Hu, M. Csete, R. Molnar, and K. Berggren, “Single-photon detectors based on ultra-narrow superconducting nanowires,” Nano Letters, vol. 11, no. 9, pp. 2048-2053, 2011. [↩]