What is a laser diode

• Energy absorption

The laser diode consists of a p-n junction in which there are holes and electrons. When a certain voltage is applied to the p-n junction, the electrons absorb energy and jump to a higher energy level. Holes are formed in the original positions of the excited electrons. The time that electrons are in an excited state without recombining with holes is very short, and the recombination time of most laser diodes is about one nanosecond.

• Spontaneous emission

At the end of the excited state lifetime of electrons, they recombine with holes. When the electron falls from a higher energy level to a lower energy level, the difference in energy is converted into photons, or electromagnetic radiation.

• Stimulated emission

We need more coherent spontaneous emission of photons emitted from the laser diode in the process. Partial mirrors are used on both sides of the diode to trap the photons released by spontaneous emission in the p-n junction until their concentration reaches a threshold. This results in the release of more photons, the photons with a photon in the same initial phase, the output is amplified. Once the photon concentration exceeds the threshold value, they will escape from the partially reflective mirror, resulting in a bright monochromatic coherent light.

Applications of a Laser Diode

Laser diode modules are widely used:

Consumer electronics: players, printers, fiber optic communications, etc.

Medical equipment: some tissue removal operations, etc.

Autonomous vehicles: Lidar systems for autonomous driving

Scientific instruments: remote non-contact measurement, spectrometry, rangefinder and other equipment.

Industrial applications: precise cutting of materials, they are also used for 3D printing to soften substrates.