Nanoscale Optical Detector with Single-Photon and Multiphoton Sensitivity

We present the first nanoscale (down to ?50 × 50 nm2) detector displaying single-photon sensitivity and a nanosecond response. This type of nanodetector can also be operated in multiphoton mode, where the detection threshold can be set at N ) 1, 2, 3, or 4 photons, thus allowing the mapping of photon number statistics on the nanoscale. Its operation principle based on that of hot-spot formation in superconducting nanowires allies the temporal resolution and sensitivity of superconducting single-photon detectors with subwavelength resolution and photon number discrimination. Such detectors can be of great interest for the study of nanophotonic devices at low temperature.