Polarization-insensitive fiber-coupled superconducting-nanowire single photon detector using a high-index dielectric capping layer
Résumé
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.