Single-Photon Avalanche Diode

SPAD（单光子雪崩二极管）SPADAdvanced

A photodetector sensitive enough to register a single photon, at the core of dToF lidar and ranging chips.

A SPAD is a photodiode operated in Geiger mode (reverse-biased above its breakdown voltage), where a single incoming photon can trigger an avalanche of current, recording the precise moment the photon arrived. It is the key component behind direct time-of-flight (dToF) ranging, which fires a laser pulse and directly measures the round-trip time of its echo: paired with time-to-digital converter circuitry, building a histogram of when large numbers of photons arrive lets the system compute distance. SPAD arrays let lidar be built as chip-based, solid-state devices, lowering cost and size, which is why they show up in automotive lidar, phone ranging modules, and the small dToF sensors used in robotics.

ExampleMany solid-state and hybrid solid-state lidars use a SPAD array chip on the receiving side, paired with a VCSEL emitter, to do dToF ranging.

Also called: SPAD
Related: Direct Time of Flight · Solid-State LiDAR · Vertical-Cavity Surface-Emitting Laser · LiDAR · Adaps Photonics
Sources: Single-photon avalanche diode - Wikipedia