Optimized Illumination Directions of Single-Photon Detectors Integrated with Different Plasmonic Structures

M. Csete[1], Á. Sipos[1], A. Szalai[1], G. Szabó[1]
[1]Department of Optics and Quantum Electronics, University of Szeged, Szeged, Hungary

The optimal orientations of different single-photon detector designs were determined by COMSOL software package. Absorption of niobium-nitride (NbN) stripes in two different (p=220 nm, 3p=660 nm) periodic patterns integrated with plasmonic elements was studied. In OC-SNSPDs consisting of ~quarter-photon-wavelength nano-cavity the optimum direction is perpendicular incidence onto NbN stripes in P-orientation. Improved absorptance is attainable in S-orientation of nano-cavity-array integrated NCAI-SNSPDs, and of nano-cavity-deflector-array integrated NCDAI-SNSPD. In short-periodic NCAI-SNSPD polar-angle-independent perfect absorptance is achievable, while in long-periodic NCAI-SNSPD surface waves result in absorptance enhancement at specific orientations. Illumination of long-periodic NCDAI-SNSPDs at polar angle corresponding to double resonance condition makes possible to reach 82% absorptance due to E-field enhancement via plasmonic modes resonant in nano-cavities and propagating below NbN stripes.