fotodetectorsensor

Fotodetectorsensor, also known as a photodetector, is a device that converts light into an electrical signal. It plays a central role in optical sensing and communication systems. Most photodetectors operate by generating an electric current or voltage when photons are absorbed, with the magnitude proportional to light intensity within a given range.

Common types include photodiodes (silicon, germanium, InGaAs), avalanche photodiodes (APD), photomultiplier tubes (PMT), and photoresistors. Image sensors such as CCD and CMOS also function as array photodetectors. The choice depends on spectral range, speed, gain, and noise requirements.

Photodiodes can operate in photovoltaic mode (no bias) or photoconductive mode (reverse-biased). APDs provide internal gain through avalanche multiplication. PMTs offer very high sensitivity but require vacuum tubes and high voltage.

Key parameters include responsivity (A/W), spectral responsivity, quantum efficiency, detectivity (D*), noise-equivalent power, linearity, and response time. Temperature affects dark current and noise; materials determine spectral range.

In a system, the photodetector is followed by a transimpedance amplifier to convert current to voltage, and then by filtering, amplification, and analog-to-digital conversion.

Applications span fiber-optic communication, astronomy, spectroscopy, environmental monitoring, medical imaging, consumer cameras, and safety sensors.

For visible light, silicon is common; infrared uses InGaAs or Ge; specialized detectors include HgCdTe for mid-IR. Research focuses on higher responsivity, broader spectral range, room-temperature operation, integration with electronics, and array-based sensing.