MTL Annual Report

We designed and fabricated superconducting nanowire single-photon detectors (SNSPDs) with nano-optical antennae to reduce the length of the nanowire needed for efficient optical coupling.  In our design, we increased the pitch of the meander and added a gold nano-optical antenna structure together with a top reflector to enhance the absorptance of the niobium nitride (NbN) nanowire for transverse-magnetically (TM) polarized incident light.  This structure simultaneously suppressed the absorptance of transverse-electrically (TE) polarized light.  The mechanism by which the antennae increase the absorption of TM-polarized light can be understood by modeling the structure as an array of slot waveguides.  We experimentally demonstrated 47% device efficiency for a 9 mm × 9 mm, 600-nm pitch SNSPD for the TM-polarization and 4% for the TE-polarization, consistent with theoretical predictions.  The reduction of the length of the nanowire shortened the detection efficiency recovery time for the detector after pulsing.  The total length of the antenna-coupled nanowire was 145 mm.  Compared with a typical (non-antenna coupled), 200-nm pitch SNSPD with the same area, the length of the nanowire was reduced by 2/3, and therefore the speed is expected to have been increased by a factor of 3.

At MIT Lincoln Laboratory, this work 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.

1. K.M. Rosfjord, J.K.W. Yang, E.A. Dauler, A.J. Kerman, V. Anant, B.M. Voronov, G.N. Gol’tsman, and K.K. Berggren, “Nanowire single-photon detector with an integrated optical cavity and anti-reflection coating,” Optics Express, vol. 14, issue 2, pp. 527-534, Jan. 2006. [↩]