The laser is mainly composed of several parts
1. Laser working medium
Laser generation must choose a suitable working medium, which can be gas, liquid, solid or semiconductor. Population inversion can be achieved in this medium to create the necessary conditions for lasing. Obviously, the existence of the metastable energy level is very beneficial to the realization of particle population inversion. The generated laser wavelengths include a wide range from vacuum ultraviolet to far infrared.
2. Incentive source
In order to invert the number of particles in the working medium, certain methods must be used to stimulate the atomic system to increase the number of particles in the upper energy level. Generally, gas discharge can be used to use electrons with kinetic energy to excite medium atoms, which is called electric excitation; pulse light sources can also be used to irradiate the working medium, which is called light excitation; there are also thermal excitation, chemical excitation, etc.
3. Resonant cavity
With a suitable working substance and excitation source, particle population inversion can be realized, but the intensity of stimulated radiation produced in this way is too weak to be practically applied. So people thought of using an optical resonant cavity to amplify. The so-called optical resonant cavity is actually two mirrors with high reflectivity mounted on the two ends of the laser face to face. One is almost totally reflected, and one is mostly reflected and a small amount is transmitted, so that the laser can be emitted through this mirror. The light reflected back to the working medium continues to induce new stimulated radiation, and the light is amplified. Therefore, the light oscillates back and forth in the resonant cavity, causing a chain reaction, amplifying like an avalanche, and generating intense laser light, which is output from one end of the partial reflector.
Although there are many types of lasers, the manufacturing principles are basically the same, and most of them are composed of three parts: excitation system, working medium and optical cavity.
The excitation system is a device that generates light, electricity, and chemical energy. The excitation system provides energy, so that most of the electrons in the laser material absorb energy and jump to the outer orbit of the atom, creating conditions for the release of laser light in the future. The incentives currently used mainly include light, electricity, and chemical reactions.
