Many people ask what a photodiode is. Is it the same thing as laser diode? The following small series will give you a brief talk.

Laser diode is "luminous", which is responsible for changing electric energy into light energy; Photodiodes, on the other hand, receive light, which converts optical signals into electrical signals. One is the "transmitting end" of light and the other is the "receiving end" of light.

Laser diode (LD) is actually a semiconductor laser, which has an active layer. When current passes, electrons and holes recombine to release photons. This light reflects back and forth in the cavity and forms coherent light after stimulated emission, which is what we call laser.

Photodiode, on the other hand, generates electrons and holes by absorbing photons, thus forming current. Simply put, it is used to "see the light". The greater the light intensity, the greater the output current.

Laser diode needs a more accurate driving current, which is afraid of current impact and is easy to burn if it is a little too much; Photodiodes generally work in reverse bias state, with small current and low power consumption.

Structurally, the laser diode has a resonant cavity and a reflector; Photodiode, on the other hand, does not. It should minimize carrier recombination in order to improve the response speed.