Optimized Illumination Directions of Single-Photon Detectors Integrated with Different Plasmonic Structures
M. Csete1 Á. Sipos1 A. Szalai1 G. Szabó1
1Department 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.