Optimized Superconducting Nanowire Single Photon Detectors to Maximize Absorptance
Dispersion characteristics of four types of superconducting nanowire single photon detectors, nano-cavity-array- (NCA-), nano-cavity-deflector-array- (NCDA-), nano-cavity-double-deflector-array- (NCDDA-) and nano-cavity-trench-array- (NCTA-) integrated (I-A-SNSPDs) devices was optimized in three periodicity intervals commensurate with half-, three-quarter- and one SPP wavelength. The optimal congurations capable of maximizing NbN absorptance correspond to periodicity-dependent tilting in S-orientation (90˚ azimuthal orientation). In NCAI-A-SNSPDs absorptance maxima are reached at the plasmonic Brewster angle (PBA) due to light tunneling. The absorptance maximum is attained in a wide plasmonic-pass-band in NCDAI1/2*λ-A, inside a flat-plasmonic-pass-band in NCDAI3/4*λ-A and inside a narrow plasmonic-band in NCDAIλ-A. In NCDDAI1/2*λ-A bands of strongly coupled cavity and plasmonic modes cross, in NCDDAI3/4*λ-A an inverted-plasmonic-band-gap develops, while in NCDDAIλ-A a narrow plasmonic-pass-band appears inside an inverted-minigap. The absorptance maximum is achieved in NCTAI1/2*λ-A inside a plasmonic-pass-band, in NCTAI3/4*λ-A at inverted-plasmonic-band-gap center, while in NCTAIλ-A inside an inverted-minigap. The highest 95.05% absorptance is attained at perpendicular incidence onto NCTAIλ-A. Quarter-wavelength type cavity modes contribute to the near-field enhancement around NbN segments except in NCDAIλ-A and NCDDAI3/4*λ-A. The polarization contrast is moderate in NCAIA-SNSPDs (~102). NCDAI- and NCDDAI-A-SNSPDs make possible to attain considerably large polarization contrast (~102-103 and ~103~104), while NCTAI-A-SNSPDs exhibit a weak polarization selectivity (~10-102).