Multiphoton detection in superconducting nanowires: Nonlinear optics in the detector

A Nth-order (N=1, 2, 3, 4, 5, 6) interferometric autocorrelator based on superconducting nanodetectors is presented. It provides much higher sensitivity as compared to the conventional autocorrelators using all-optical nonlinearities and a temporal resolution of about 20 ps, which is limited by the quasi-particle energy relaxation time in the superconducting films. A semiclassical model is introduced to explain the nonlinear photodetection process. A comparison of sensitivity to conventional autocorrelators is also presented. © 2013 SPIE.