Ultrasensitive N-photon interferometric autocorrelator

TL;DR

This paper introduces a highly sensitive N-photon interferometric autocorrelator using superconducting nanodetectors, achieving high temporal resolution limited by quasiparticle relaxation time, enabling advanced optical measurements.

Contribution

It presents a novel autocorrelation method combining linear absorption and nonlinear detection in superconducting nanodetectors, surpassing traditional all-optical nonlinear approaches.

Findings

Achieved temporal resolution of ~20 ps in NbN films.

Demonstrated autocorrelation measurement for N=1 to 4.

Provided a comprehensive model and comparison with existing methods.

Abstract

We demonstrate a novel method to measure the Nth-order (N=1, 2, 3, 4) interferometric autocorrelation with high sensitivity and temporal resolution. It is based on the combination of linear absorption and nonlinear detection in a superconducting nanodetector, providing much higher efficiency than methods based on all-optical nonlinearities. Its temporal resolution is only limited by the quasi-particle energy relaxation time, which is directly measured to be in the 20 ps range for the NbN films used in this work. We present a general model of interferometric autocorrelation with these nonlinear detectors and discuss the comparison with other approaches and possible improvements.