New design of a waveguide integrated photon number resolving superconducting detector with micron-wide strips

We report on the development of a design for a waveguide integrated photon number resolving superconducting detector with micron-wide strips. The detector is designed for a 1550-nm-wavelength single-mode waveguide. Using the planarization operation, it is possible to cover the waveguide and the entire area around it with a dielectric layer, producing a flat surface for the superconducting detector fabrication. The detector is formed in a shape of a straight line directly above the waveguide. The length and width of the superconducting detector are chosen to absorb maximum of the radiation from the waveguide. In the same superconductor layer, the Klopfenstein taper  impedance transformer is designed as a non-uniform coplanar line. The use of impedance matching Klopfenstein tapers makes it possible to distinguish the resistances of several hot spots, that is, to distinguish the number of  absorbed photons. The detector should absorb almost all radiation and be capable to distinguish up to 3 photons in an optical pulse.