SPAD sensor school

The SPAD Sensor School is an introductory school for students, PhDs, postdoc, and early career researchers who are not yet familiar with the SPAD technology.

The school will take place at the Humanities Hub of the Fondazione Bruno Kessler on Monday, June 3rd, 2024. Please refer to the Venue page of this website for more info on the location.

A team of experts will introduce the participants to all the aspects of SPAD technology, from the device operating principle to sensor architectures and applications.

Monday, June 3, 2024

08:30 School Welcome and Introduction

08:40 SPAD principle, main performance parameters, and device structures
Prof. Angelo Gulinatti (Politecnico di Milano) and Prof. Alberto Tosi (Politecnico di Milano)

This lecture will introduce the working principle of SPAD sensors and their performance parameter like detection efficiency, dark count rate, timing jitter, afterpulsing probability and optical crosstalk. Then, the lecture will focus on how some of these metrics are influenced by the detector structure and which are the main solutions currently adopted in Si, InGaAs/InP, and Ge-on-Si SPADs.

9:55 SPAD array architectures
Prof. Robert Henderson (University of Edinburgh) and Prof. Edoardo Charbon (EPFL)

This comprehensive lecture delves into the diverse landscape of SPAD array architectures, covering a wide spectrum of topics. It explores masked, gated, photon counting, and timestamping architectures, delving into multiplexing techniques such as OR/XOR trees, coincidence, synchronous summation, and decision trees. The lecture investigates imagers with single SPAD per pixel, highlighting quenching and recharge methods (active, passive, and hybrid). It discusses analog and digital SiPMs, as well as modular digital SiPM arrays. Resource-sharing strategies, system on a chip design, computational imaging, AI, ML, power management, and 3D-stacking challenges are also examined. Future perspectives, multi-spectral capabilities, and microlenses round out this lecture, providing a comprehensive view of SPAD array advancements.

10:55 Coffee break

11:30 Time-to-digital converters for SPAD arrays
Dr. Nicola Massari (Fondazione Bruno Kessler - FBK)

This lecture provides a concise overview of Time-to-Digital Converters (TDCs) for SPAD arrays, covering principles, various architectures, and essential performance indicators such as resolution, linearity, precision, and power consumption. Additionally, it explores the critical aspect of characterization techniques, offering a comprehensive understanding of TDCs in the context of SPAD arrays.

12:30 Lunch

14:00 How to measure – Characterization of SPAD-based detectors
Dr. Georg Röhrer (ams-OSRAM)

This lecture offers a comprehensive guide to the characterization of SPAD devices and sensors. It covers critical parameters such as breakdown voltage, dark count rate (DCR), afterpulsing, crosstalk, photon detection probability (PDP), fill-factor, and photon detection efficiency (PDE). Additionally, the lecture delves into Single-Photon Time Resolution (SPTR) and examines the impact of Process-Voltage-Temperature (PVT) variations, providing researchers and engineers with invaluable insights into the thorough evaluation and optimization of SPAD devices and sensors.

15:00 Coffee break

15:35 Applications of SPAD arrays
Dr. Claudio Bruschini (EPFL)

SPAD-based individual detectors and arrays have seen a host of applications being explored and industrialized in the past years, relying on their single-photon detection capability, combined with excellent photon-timing precision and noiseless read-out (in the digital flavor). We will first have a look at prominent examples from the bio-photonics and medical community (FLIM, Raman spectroscopy, Diffuse Optical Tomography), as well as from high-energy and medical physics (scintillator-based particle detectors, positron emission tomography). On the commercial side, successful products are already available for ranging and time-of-flight applications, from consumer to industrial, automotive and space. Finally, blue sky research in super-resolution microscopy, ghost and non-line-of-sight imaging is driving the specifications of tomorrow's sensors.