A photodetector receives light from an optical source such as an LED, laser or optical fiber. When photons enter the semiconductor material, they transfer energy to electrons. This interaction creates mobile charge carriers, producing an electrical current.

In this simulation, increasing the light intensity increases the number of photons reaching the detector. More photons produce more charge carriers and therefore a larger electrical current. This demonstrates the basic principle used by photodetectors in optical communication systems.

Optical Fiber Communication: Photodetectors at the receiving end of an optical fiber convert the incoming optical signal into an electrical signal.

Automatic Lighting: Light sensors detect environmental brightness and control lamps automatically.

Cameras and Imaging: Light-sensitive semiconductor devices convert incoming light into electrical information used to create images.

Remote Controls: Photodetectors receive infrared signals from remote-control devices.

Industrial Sensors: They can detect objects, measure light intensity, count products and monitor processes.

For an ideal photodiode operating in its normal region, the photocurrent is approximately proportional to the incident optical power:

I_ph ≈ R × P_opt

where I_ph is photocurrent, R is detector responsivity, and P_opt is incident optical power. Therefore, stronger light generally produces a larger detector current.