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The Light-emitting and Working Principle of Semiconductor Laser

Aug 13, 2020

Semiconductor lasers, also known as laser diodes, are lasers that use semiconductor materials as working materials. It has the characteristics of small size and long lifespan, and can use simple injection current to pump its working voltage and current compatible with integrated circuits, so it can be monolithically integrated.

Due to these advantages, semiconductor diode lasers have been widely used in laser communications, optical storage, optical gyroscopes, laser printing, ranging and radar.

 

The principle of laser light emission

The laser must meet the following conditions:

1. The population reversal;

2. There must be a resonant cavity, which can play the role of optical feedback and form laser oscillation; the formation of various forms, the simplest is the Fabry-Parrot resonant cavity.

3.Third, the laser must meet the threshold condition, that is, the gain must be greater than the total loss.

 

Semiconductor laser characteristics

Semiconductor laser is a type of laser device with semiconductor material as the working substance. It was born in 1962. In addition to the common characteristics of lasers, it also has the following advantages: 

(1) Small size and light weight;

(2) Low driving power and current; 

(3) High efficiency and long working life;

(4) It can be directly modulated by electricity;

(5) It is easy to realize optoelectronic integration with various optoelectronic devices;

(6) Compatible with semiconductor manufacturing technology; mass production is possible.

Because of these characteristics, semiconductor lasers have received extensive attention and research from all over the world since their inception. It has become the fastest growing, most widely used laser in the world, the first to get out of the laboratory for commercialization, and the largest output value.

 激光二极管原理图

Working principle of semiconductor laser

The working principle of semiconductor lasers is the excitation method, which uses semiconductor materials (that is, the use of electrons) to transition between energy bands to emit light. The cleavage surface of the semiconductor crystal forms two parallel mirrors as mirrors to form a resonant cavity to make light oscillate and feedback. The radiation that generates light is amplified and laser light is output.

Semiconductor lasers work by injecting carriers. Three basic conditions must be met for laser emission:

(1) To produce sufficient population inversion distribution, that is, the number of high-energy state particles is sufficiently larger than that of low-energy state;

(2) There is a suitable resonant cavity that can play a feedback function, so that the stimulated emission photons are proliferated, thereby generating laser oscillation;

(3) A certain threshold condition must be met to make the photon gain equal to or greater than the photon loss.