Imagers that use their own illumination can capture three-dimensional (3D) structure and reflectivity information. With photon-counting detectors, images can be acquired at extremely low photon fluxes. To suppress the Poisson noise inherent in low-flux operation, such imagers typically require hundreds of detected photons per pixel for accurate range and reflectivity determination. We introduce a low-flux imaging technique, called first-photon imaging, which is a computational imager that exploits spatial correlations found in real-world scenes and the physics of low-flux measurements. Our technique recovers 3D structure and reflectivity from the first detected photon at each pixel. We demonstrate simultaneous acquisition of sub-pulse duration range and 4-bit reflectivity information in the presence of high background noise. First-photon imaging may be of considerable value to both microscopy and remote sensing.

https://science.sciencemag.org/content/sci/343/6166/58.full.pdf

First-Photon Imaging

A superconducting nanowire acting as a single-photon detector and as a microwave delay line is used to demonstrate an imaging device at the single-photon level with sub-20-µm spatial resolution and 50-ps temporal resolution.

Single-photon imager based on a superconducting nanowire delay line

In this paper we intend to give a comprehensive description of the current understanding of the
detection mechanism in superconducting nanowire single-photon detectors. We will review key
experimental results related to the detection mechanism, e.g. the variations of the detection
probability as a function of bias current, temperature or magnetic field. Commonly used
detection models will be introduced and we will analyze their predictions in view of the
experimental observations. Although none of the proposed detection models is able to describe
all experimental data, it is becoming increasingly clear that vortices are essential for the
formation of the initial normal-conducting domain that triggers a detection event.

/pdf/detection-mechanism-of-superconducting-nanowire-single-1nh88cl751.pdf

Detection mechanism of superconducting nanowire single-photon detectors

Abstract Integration of superconducting nanowire single-photon detectors with nanophotonic waveguides is a key technological step that enables a broad range of classical and quantum technologies on chip-scale platforms. The excellent detection efficiency, timing and noise performance of these detectors have sparked growing interest over the last decade and have found use in diverse applications. Almost 10 years after the first waveguide-coupled superconducting detectors were proposed, here, we review the performance metrics of these devices, compare both superconducting and dielectric waveguide material systems and present prominent emerging applications.

/pdf/waveguide-integrated-superconducting-nanowire-single-photon-3za40qenjp.pdf

Waveguide-integrated superconducting nanowire single-photon detectors

Jitter is one of the key parameters for a superconducting nanowire single photon detector (SNSPD). Using an optimized time-correlated single photon counting system for jitter measurement, we extensively studied the dependence of system jitter on the bias current and working temperature. The signal-to-noise ratio of the single-photon-response pulse was proven to be an important factor in system jitter. The final system jitter was reduced to 18 ps by using a high-critical-current SNSPD, which showed an intrinsic SNSPD jitter of 15 ps. A laser ranging experiment using a 15-ps SNSPD achieved a record depth resolution of 3 mm at a wavelength of 1550 nm.

Jitter analysis of a superconducting nanowire single photon detector

We developed a time-correlated single-photon counting (TCSPC) system based on the low-jitter superconducting nanowire single-photon detection (SNSPD) technology. The causes of jitters in the TCSPC system were analyzed. Owing to the low jitter of the SNSPD technology, a system jitter of 26.8 ps full width at half-maximum was achieved after optimizing the system. We demonstrated time-of-flight laser ranging at 1550 nm wavelength at a standoff distance of 115 m based on this TCSPC system. A depth resolution of 4 mm was achieved directly by locating the centroids of each of the two return signals. Laser imaging was also performed using the TCSPC system. This low-jitter TCSPC system using the SNSPD technology presents great potential in long-range measurements and imaging applications for low-energy-level and eye-safe laser systems.

Time-of-flight laser ranging and imaging at 1550 nm using low-jitter superconducting nanowire single-photon detection system.

We developed a time-correlated single-photon counting (TCSPC) system based on the low-jitter superconducting nanowire single-photon detection (SNSPD) technology. The causes of jitters in the TCSPC system were analyzed. Owing to the low jitter of the SNSPD technology, a system jitter of 26.8 ps full-width at half-maximum was achieved after optimizing the system. We demonstrated time-of-flight laser ranging at 1550 nm wavelength at a stand-off distance of 115 m, based on this TCSPC system. A depth resolution of 4 mm was achieved directly by locating the centroids of each of the two return signals. Laser imaging was also performed using the TCSPC system. This low-jitter TCSPC system using the SNSPD technology presents great potential in long-range measurements and imaging applications for low-energy-level and eye-safe laser systems

Wenxing Zhang

Papers

Jitter analysis of a superconducting nanowire single photon detector

Jitter analysis of a superconducting nanowire single photon detector

Time-of-flight laser ranging and imaging at 1550 nm using low-jitter superconducting nanowire single-photon detection system.

Time-of-flight laser ranging and imaging at 1550 nm using low-jitter superconducting nanowire single-photon detection system