{"id":2071,"date":"2010-07-14T13:05:04","date_gmt":"2010-07-14T17:05:04","guid":{"rendered":"https:\/\/wpmu2.mit.local\/?p=2071"},"modified":"2010-07-27T10:53:44","modified_gmt":"2010-07-27T14:53:44","slug":"superconducting-nanowire-single-photon-detectors-based-on-30-nm-wide-nanowires","status":"publish","type":"post","link":"https:\/\/wpmu2.mit.local\/superconducting-nanowire-single-photon-detectors-based-on-30-nm-wide-nanowires\/","title":{"rendered":"Superconducting Nanowire Single-photon-detectors Based on 30-nm-wide Nanowires"},"content":{"rendered":"

In order to improve the sensitivity of superconducting nanowire single-photon-detectors (SNSPDs [1<\/a>]<\/sup> ) at telecom wavelengths and extend it to the middle infrared range, we fabricated SNSPDs based on 30-nm-wide nanowires (see Figure 1).<\/p>\n

To make the photodetection pulse detectable with standard room-temperature electronics, N<\/em> nanowires were arranged in a parallel architecture such that when one section fired, the current flowing through the whole device was redirected to the read-out circuitry (Superconducting Nanowire Avalanche Photodetector: SNAP) [2<\/a>]<\/sup>. The signal-to-noise ratio was then N<\/em> times higher than with a series design.<\/p>\n

The single-photon detection efficiency (DE<\/em>) of 30-nm-wide nanowire SNSPDs and of 2-, 3- and 4-section SNAPs was measured for 1550-nm wavelength at a temperature of 4.7 K. The DE<\/em> exhibited a reduced dependence on the bias current (I<\/em>B<\/sub>) compared with 100-nm-wide SNSPDs. This reduced dependence allowed operating narrow SNSPDs at an I<\/em>B<\/sub> (~ 50 % of the critical current I<\/em>C<\/sub>) far lower than with wide SNSPDs (typically ~ 95 % of I<\/em>C<\/sub>) for the same DE<\/em>. This reduction in the operating bias current would in principle improve the detector sensitivity, as the dark count rate (DK<\/em>) of SNSPDs decreases exponentially with I<\/em>B<\/sub>. However, the highest DE<\/em> measured at 0.5 I<\/em>C<\/sub> was 7% for a DK<\/em> = 100 Hz, which does not represent an improvement to the sensitivity of wide SNSPDs. This performance occurred in part due to the low fill factor (f = 30 %) of the device\u2019s active area, due to the high operating temperature, and due to the background-radiation-induced dark counts.<\/p>\n

The work at Lincoln Lab was sponsored by the United States 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