On-chip, photon-number-resolving, telecom-band detectors for scalable photonic information processing

We demonstrate an integrated photon-number resolving detector, operating in the telecom band at 1550 nm, employing an evanescently coupled design that allows the detector to be placed at arbitrary locations within a planar optical circuit. Up to 5 photons are resolved in the guided optical mode via absorption from the evanescent field into a tungsten transition-edge sensor. The detection efficiency of the absorbing tungsten region is 7.2 %.