Photon-Number Discrimination from Increasing Time-of-Arrival Separation in Wide Superconducting Microstrip Single-Photon Detectors

arXiv:2610.32154v1 Announce Type: new Abstract: Measurements of photon-number-dependent time-of-arrival (TOA) distributions in wide NbN superconducting microstrip single-photon detectors (SMSPDs) are presented. Two \SI{10}{\um}-long devices with widths of \SI{3.2}{\um} and \SI{6.4}{\um} are characterized under pulsed \SI{515}{nm} excitation. The TOA histograms are described by sums of exponentially modified Gaussian (EMG) components, with the wider device exhibiting components assigned to photon numbers up to \(n=8\). Adjacent TOA peaks become more distinguishable relative to their widths at higher photon number, in contrast to the compression of neighboring photon-number timing shifts observed in conventional narrow-wire SNSPDs.