Single-photon avalanche diode (SPAD)

What is a Single-Photon Avalanche Diode (SPAD)?

A Single-Photon Avalanche Diode (SPAD) is a type of photodiode that is capable of detecting and measuring very low levels of light. It is a highly sensitive device that can detect individual photons of light, making it useful for applications where low light levels are present. SPADs are commonly used in scientific research, medical imaging, and communication technology.

How does a SPAD work?

A SPAD works by using an avalanche effect to amplify the signal produced by a single photon of light. When a photon strikes the SPAD, it generates an electron-hole pair, which in turn triggers a high voltage pulse. This pulse causes the SPAD to avalanche, creating a large number of electron-hole pairs, which are then measured as a signal. This process makes SPADs extremely sensitive and allows them to detect individual photons of light.

Applications of SPAD technology

SPAD technology has a wide range of applications in fields such as quantum physics, telecommunications, and medical imaging. In quantum physics, SPADs are used to detect and measure single photons of light, which are important for studying the behavior of particles at the quantum level. In telecommunications, SPADs are used as detectors in optical communication systems, where they can detect very weak signals over long distances. In medical imaging, SPADs are used in imaging systems such as positron emission tomography (PET) scanners, where they can help to improve the resolution and sensitivity of the images produced.

Example of SPAD in practical use

One practical example of SPAD technology in use is in LiDAR (Light Detection and Ranging) systems for autonomous vehicles. LiDAR systems use lasers to emit pulses of light, which bounce off objects in the environment and are then detected by a sensor. By measuring the time it takes for the light to bounce back, the LiDAR system can create a 3D map of the surrounding area. SPADs are used in LiDAR systems to detect the returning pulses of light, which are often very weak. The high sensitivity of SPADs makes them well-suited for this application, as they can detect even the weakest signals and accurately measure the distance to objects in the environment.