The working principle of laser

It is precisely because of the emergence of lasers that optical fiber communication has benefited mankind. A very simple introduction to the working principle of the laser.

To produce laser light, the laser needs to achieve the following goals.

Pump source

It is used to extract the particles of the laser working substance from the ground state to a high energy level to achieve population inversion.

Laser working substance

1. The laser working substance and the pump source jointly realize the population inversion, which requires this substance to have the ability to achieve the population inversion to a greater extent, so that the pump source can easily perform the extraction from low to high energy levels .
2. The laser working material also undertakes the work of realizing stimulated radiation.
3. The working substance of the laser determines the wavelength at which the laser can generate laser light. The laser wavelength is determined by the transition between two energy levels forming laser radiation in the substance.

Optical cavity

That is, the two mirrors in the picture.

1. Generate and maintain laser oscillation. Through the continuous reflection between the two mirrors, the length of the laser working material can be extended, so that the stimulated radiation exceeds the spontaneous radiation to become dominant, and the stimulated radiation is further expanded so that the laser energy generated is greater than the loss on the way.
2. Control the quality of the output laser beam. The resonant cavity can limit the direction and frequency of the oscillating beam in the cavity to ensure high monochromaticity and high direction of the output laser. By adjusting the geometric parameters of the optical resonant cavity, the lateral distribution characteristics of the beam, the spot size, the oscillation frequency, and the beam divergence angle can also be directly controlled.
3. The right half mirror also plays a role in laser output. In addition, some devices can be added to the optical resonant cavity to effectively control the characteristics of the output laser.