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(Color online) (a) Schematic view and (b) Contour and vector plot of the amplitude [V/m] and direction of the electric field for the fundamental mode (λ = 1300 nm) of the waveguide superconducting single-photon detector.
(Color online) (a) Scanning electron microscope (SEM) micrograph of Ti/Au electric contacts; (b) Collection of three SEM micrographs taken in different regions of a 30 μm long WSPD, the nanowires are still covered by the HSQ etching mask; (c) Atomic force microscope (AFM) image of the 1.85 μm wide and 30 μm long HSQ mask used for the etching of the waveguide aligned on top of the NbN nanowires; and d) AFM Enlarged view of the waveguide HSQ etching mask showing a realignment accuracy better than 100 nm.
(Color online) Count rate as a function of laser power (λ = 1300 nm, TE polarization, Ib = 9.9 μA), showing a linear behavior and hence operation in the single-photon regime. Inset: Current-voltage characteristic of the WSPD, showing a critical current of 16.9 μA, the relaxation-oscillation region, and the beginning of the hot-spot plateau.
(Color online) Device QE (open symbols) and system QE (closed symbols) of a 50 μm-long WSPD under illumination at 1300 nm in the TE polarization (left axis) and dark count rate (black dots, right axis) as a function of the normalized bias current. Inset: WSPD output pulse after 48 dB amplification.
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