Sub-diffraction limited imaging at 3.2km: SNSPD-based single-photon laser reflective tomography

Overcoming the diffraction limit has been a subject of extensive research, particularly in over extra-long ranges. Laser reflective tomography (LRT), whose resolution is solely dependent on the system temporal jitter, has attracted attention in the field of long-range space target detection. Single-photon LRT employing time-correlated single-photon counting (TCSPC) technology can achieve picosecond-level temporal resolution while maintaining high signal-to-Background ratios. Superconducting nanowire single photon detectors (SNSPDs) emerged in the last decade as a disruptive technology that features performance characteristic, such as high sensitivity, and temporal accuracy, which are ideally suited for single-photon LRT. This study presents a high-performance RTL system, experimentally demonstrating single-photon imaging beyond the diffraction limit at a stand-off distance of 3.2km under varying daylight conditions. According to the Rayleigh criterion, the transversal resolution (8mm line pair) is about twice of the optical diffraction limit. The results demonstrate the robust long-range imaging capabilities of the system.