The lasers mainly consist of three major components. These are Active medium, Pump, and resonator guide.
First we will discuss active medium. It can be in molecular or in atomic state.
E.g., He, Ne, CO2, etc. It does the work of decreasing the radiativity from E2 to E1 level i.e. from higher to lower energy level.
Pump is used for the achievement of population inversion. Pumping can be done in two ways. One is electrical discharge method and other is optical method. In optical method a flash lamp is used. This flash lamp is also used in ruby laser. This type of pumping is good for active gaseous medium.
Third one is Resonator guide. It basically provides the guidance about the simulated emission process. It is induced by high speed photons. Finally, a laser beam will be generated.
In other words if we will analyze the resonator guide then we will see that it is simply a pair of two plane mirrors M1 and M2. Both the mirrors are set up on an axis known as optic axis. Both the mirrors are placed parallel to each other. Mirror M1 is totally reflecting mirror but on the other hand mirror M2 is partially reflecting. An active medium is used between the both mirrors. This whole arrangement only filters those photons which came along the axis. All the other photons are rejected. This is the major reason that a laser beam having very high intensity is produced.
