**6. Optical resonator**

Each laser optical resonator consists of two mirrors and a pumping chamber, containing the active laser medium. Generally, one of the mirrors is a full reflector (input coupler), while the other is a partial reflector (output coupler). Photons, which are moving in the direction of the resonator axis are resonated to form the laser beam. Photons in other directions are destructed by adsorption on the walls of the active medium (**Figure 8**) [3–7].

**Figure 8.** *The function of the optical resonator during laser beam production.*

**Figure 9.** *The key components of laser welding procedure.*
