We all know that you may not see many photodiodes in your daily life, but we will definitely need photodiodes when buying laser diodes, so you must know what products they are. Today, Xiaobian will tell you about the working principle and characteristics of photodiodes.

What are photodiodes for?

Photodiode, to put it bluntly, is an element that converts optical signals into electrical signals.

It looks like an ordinary diode, but its function is completely different. Ordinary diodes are "conductive" and photodiodes are "photosensitive".

When light shines on its PN junction, electrons and holes will be generated, and these charges will be separated under the action of electric field, thus forming a current. This current varies with the light intensity, so by measuring this current, we can know how strong the light is.

Main characteristics of photodiode

Fast response speed

It is particularly sensitive to the change of optical signal, and its response time can be microsecond or even nanosecond. Therefore, it is standard in fields that need high-speed response, such as optical communication, laser ranging and bar code scanning.

Low dark current

Dark current is the leakage current when there is no light. A good photodiode has a very low dark current, which can ensure that the signal is still clean under weak light conditions.

Wide spectral response range

Photodiodes of different materials are sensitive to light in different bands, such as:

Silicon (Si) photodiode: most sensitive to visible light and near infrared.

Germanium (Ge) or gallium arsenide (GaAs): Better response to infrared light.

This also determines its adaptability in different fields such as ultraviolet detection, infrared remote sensing and laser ranging.

The essence of photodiode is to turn light into electricity; Its advantages are fast, stable, accurate and cheap. It is precisely because of these characteristics that it can occupy the leading role in various laser, optical and detection equipment for a long time.