Lasers consist of three components:
1. An external pump source. This component guides external energy to the laser.
2. The active laser medium. The active laser medium is located on the inside of the laser. Depending on the design, the laser medium can consist of a gas mixture (CO2 laser), of a crystal body (YAG laser) or glass fibers (fiber laser). When energy is fed to the laser medium through the pump, it emits energy in the form of radiation.
3. The resonator. The active laser medium is located between two mirrors, the "resonator." One of these mirrors is a one-way mirror. The radiation of the active laser medium is amplified in the resonator. At the same time, only a certain radiation can leave the resonator through the one-way mirror. This bundled radiation is the laser radiation.