Laser has three important basic components namely,

(i) Active medium

The medium at which the population inversion takes place.

(ii) Pumping system

Pumping system is a device. By using this device population inversion can be achieved in the active material.

(iii) Optical resonator

A pair of reflecting surfaces of which one is fully reflecting and the other is partially reflecting form in optical resonator. Thus, an optical resonator is a device that directs the photons back and forth through the laser medium and the number of photons get multiplied by stimulated emission to achieve a coherent laser radiations.

Fig. (1) Optical resonator