{"id":2819,"date":"2011-07-19T15:06:25","date_gmt":"2011-07-19T15:06:25","guid":{"rendered":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/?p=2819"},"modified":"2011-07-19T21:02:13","modified_gmt":"2011-07-19T21:02:13","slug":"single-photon-detection-with-ultranarrow-superconducting-nanowires","status":"publish","type":"post","link":"https:\/\/mtlsites.mit.edu\/annual_reports\/2011\/single-photon-detection-with-ultranarrow-superconducting-nanowires\/","title":{"rendered":"Single-Photon Detection with Ultranarrow Superconducting Nanowires"},"content":{"rendered":"

Superconducting nanowire single-photon detectors (SNSPDs) [1<\/a>] <\/sup> perform single-photon counting in the near\u2011infrared 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 \u00b5m wavelength (\u03bb<\/em>). We developed SNSPDs based on ultra-narrow (30- to 10-nm-wide) superconducting nanowires [2<\/a>] <\/sup>, which showed improved robustness to constrictions and higher sensitivity to near-infrared photons with respect to standard SNSPDs.<\/p>\n

As shown in Figure 1, at \u03bb<\/em> =\u00a01550\u00a0nm our 30\u00a0nm nanowire\u2011width SNSPDs could be biased far from the device critical current (I<\/em>C<\/sub>) with minimal loss in detection efficiency (\u03b7<\/em>), so even heavily\u2011constricted devices could reach the same efficiency as constriction\u2011free ones.<\/p>\n

As shown in Figure 2 a, varying \u03bb<\/em> from 700 to 2100 nm, the \u03b7<\/em> vs bias current (I<\/em>B<\/sub>) curves of 30\u00a0nm nanowire\u2011width SNSPDs kept a sigmoidal shape, with the cut-off current (I<\/em>co<\/sub>, taken to be at the inflection point of the \u03b7<\/em> vs I<\/em>B<\/sub> curves) increasing from 0.31 I<\/em>C<\/sub> to 0.41 I<\/em>C<\/sub>. For 90\u00a0nm nanowire\u2011width detectors (shown in Figure 2 b), I<\/em>co<\/sub> increased from 0.64 I<\/em>C<\/sub> at \u03bb <\/em>= 500 nm to 0.89 I<\/em>C<\/sub> at \u03bb <\/em>= 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.<\/p>\n

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.<\/p>\n\n\t\t