Avalanche photodetector (APD photodetector) is a semiconductor photodetector that utilizes avalanche multiplication effect to amplify internal signals. It generates a strong electric field inside the device through high reverse bias voltage (usually tens to hundreds of volts), amplifies weak optical signals into measurable strong electrical signals, and has the characteristics of high gain, high sensitivity, and fast response.
1.Avalanche photodetector Core working principle
Optoelectronic conversion: Photons are incident on the photosensitive region of APD and absorbed, producing electron hole pairs.
Avalanche multiplication: Under the action of a strong electric field, photo generated carriers are accelerated and collide with lattice atoms to ionize, generating new electron hole pairs and forming a chain multiplication (similar to the “avalanche” effect), which increases the internal gain of photocurrent by tens to thousands of times, greatly improving the detection sensitivity of weak optical signals.
2.Avalanche photodetector Core Features
2.1High gain and high sensitivity: capable of detecting extremely weak light signals (about 10 times more sensitive than ordinary photodiodes), suitable for low light detection scenarios.
2.2Fast response speed: The response speed can reach nanoseconds, suitable for high-speed optical signal detection (such as high-speed optical communication).
2.3Good linearity: The output current has a good linear relationship with the incident light intensity, which can measure both distance (through light intensity) and reflectivity.
2.4Relatively high noise: Due to the multiplication process of avalanche, the noise of APD is slightly higher than that of ordinary photodiodes, and the gain varies with temperature, usually requiring a temperature compensation circuit.
3.Main application areas
3.1Lidar: As the core component of the LiDAR receiver, it is used for long-distance, low reflectivity detection in scenarios such as vehicles, drones, and surveying.
3.2Fiber optic communication: used for receiving weak optical signals in long-distance, high-speed optical communication systems.
3.3Weak light detection: applied in fields such as quantum communication, biomedical imaging (such as PET scanning, fluorescence detection), deep space exploration, laser ranging, and industrial detection.
Note: When APD photodetector operates at high reverse bias (close to breakdown voltage) and is paired with a quenching circuit, it can operate in “Geiger mode” and can be used as a single photon avalanche photodiode (SPAD) for high-sensitivity detection at the single photon level.
Post time: Sep-18-2026