Light Detection and Ranging (LiDAR) is a 3D imaging technique, widely used in many applications such as augmented reality, automotive, machine vision, spacecraft navigation and landing. Achieving long-ranges and high-speed, most of all in outdoor applications with strong solar background illumination, are challenging requirements. In the introduction we review different 3D-ranging techniques (stereo-vision, projection with structured light, pulsed-LiDAR, amplitude-modulated continuous-wave LiDAR, frequency-modulated continuous-wave interferometry), illumination schemes (single point and blade scanning, flash-LiDAR) and time-resolved detectors for LiDAR (EM-CCD, I-CCD, APD, SPAD, SiPM). Then, we provide an extensive review of silicon- single photon avalanche diode (SPAD)-based LiDAR detectors (both commercial products and research prototypes) analyzing how each architecture faces the main challenges of LiDAR (i.e., long ranges, centimeter resolution, large field-of-view and high angular resolution, high operation speed, background immunity, eye-safety and multi-camera operation). Recent progresses in 3D stacking technologies provided an important step forward in SPAD array development, allowing to reach smaller pitch, higher pixel count and more complex processing electronics. In the conclusions, we provide some guidelines for the design of next generation SPAD-LiDAR detectors.

Quantum imaging and microscopy profit from quantum correlations and entanglement to image objects and samples with resolution and sensitivity that goes far beyond what can be achieved through classical optics. In order to carry out these techniques, suitable detectors with specific features must be employed. This paper aims to highlight the importance of sensors based on single photon avalanche diodes (SPAD) in quantum imaging and microscopy applications, paving the way for the next-generation ideal quantum imager. After reviewing the main techniques (based on quantum physics principles) for improving the resolution and sensitivity of a sample image, the pros and cons of different sensors, such as avalanche photodiodes (APDs), and the intensified and electron-multiplying charge coupled devices (ICCDs and EMCCDs), are identified. Then the analysis mainly focuses on SPAD-based detectors, identified as the best candidates for quantum imaging, critically discussing the requirements and performance, also in relation to already existing SPAD-based architectures with specific features fitting the application. Eventually, next-generation quantum imagers should integrate together all the best architectural choices herewith presented, so as to detect photon coincidences and to perform efficient event-driven readout, also by exploiting a suitable technology and SPAD design to optimize the discussed detection performance.

Light Detection and Ranging (LiDAR) is a widespread technique for 3D ranging and has widespread use in most automated systems that must interact with the external environment, for instance in industrial and security applications. In this work, we study a novel architecture for Single Photon Avalanche Diode (SPAD) arrays suitable for handheld single point rangefinders, which is aimed at the identification of the objects’ position in the presence of strong ambient background illumination. The system will be developed for an industrial environment, and the array targets a distance range of about 1 m and a precision of few centimeters. Since the laser spot illuminates only a small portion of the array, while all pixels are exposed to background illumination, we propose and validate through Monte Carlo simulations a novel architecture for the identification of the pixels illuminated by the laser spot to perform an adaptive laser spot tracking and a smart sharing of the timing electronics, thus significantly improving the accuracy of the distance measurement. Such a novel architecture represents a robust and effective approach to develop SPAD arrays for industrial applications with extremely high background illumination.

In this paper, we present the architecture and the experimental characterization of an improved version of a previously developed 32 × 32 Single Photon Avalanche Diodes (SPADs) and Time to Digital Converters (TDCs) array, and two new arrays (with 8 × 8 and 128 × 1 pixels) with the additional capability of actively gating the detectors with subnanosecond rise time. The arrays include high performance SPADs (0.04 cps/µm 2 , 50% peak PDE) and provide down to 410 ps Full-Width at Half-Maximum (FWHM) single shot precision and excellent linearity. We developed a camera to exploit these imagers in timeresolved, single-photon applications.

Single-photon avalanche diode (SPAD) exploitation in high-flux applications is often hindered by the trade-off between the SPAD dead-time and afterpulsing probability. In this paper, we present the architecture and the experimental characterization of two chips including a novel SPAD sensing, and readout scheme designed to minimize dead-time (1.78 ns and 0.93 ns respectively) and afterpulsing probability (0.14% maximum). We have coupled this architecture with high-performance SPADs obtaining an extremely stable dead-time (6.44 ps rms jitter) that can be easily regulated through an external voltage. Thanks to its compact size, this novel pixel architecture can be easily integrated within high-resolution SPAD arrays for GHz applications.