Polarization-insensitive fiber-coupled superconducting-nanowire single photon detector using a high-index dielectric capping layer
Anna Mukhtarova (Université Grenoble Alpes)
Luca Redaelli (Université Grenoble Alpes)
Dibyendu Hazra (Université Grenoble Alpes)
Houssaine Machhadani (Université Grenoble Alpes)
Stéphane Lequien (Université Grenoble Alpes)
Max Hofheinz (Université Grenoble Alpes)
Jean Luc Thomassin (Université Grenoble Alpes)
Frederic Gustavo (Université Grenoble Alpes)
Julien Zichi (KTH Royal Institute of Technology)
Val Zwiller (Kavli institute of nanoscience Delft, TU Delft - QN/Zwiller Lab, KTH Royal Institute of Technology, Université Grenoble Alpes)
Eva Monroy (Université Grenoble Alpes)
Jean Michel Gérard (Université Grenoble Alpes)
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Abstract
Superconducting-nanowire single photon detectors (SNSPDs) are able to reach near-unity detection efficiency in the infrared spectral range. However, due to the intrinsic asymmetry of nanowires, SNSPDs are usually very sensitive to the polarization of the incident radiation, their responsivity being maximum for light polarized parallel to the nanowire length (transverse-electric (TE) polarization). Here, we report on the reduction of the polarization sensitivity obtained by capping NbN-based SNSPDs with a high-index SiNx dielectric layer, which reduces the permittivity mismatch between the NbN wire and the surrounding area. Experimentally, a polarization sensitivity below 0.1 is obtained both at 1.31 and 1.55 µm, in excellent agreement with simulations.