How the laser works.

In addition to the free electron laser, all kinds of lasers have the same basic working principle. Lasing population inversion is a sine qua non and gain greater than the loss, so the essential component in the device with incentive or pumping source, with the working medium of metastable energy levels of two parts.Excitation is the excitation state after absorbing the external energy by the working medium and creating conditions for the realization and maintenance of the inversion of the number of particles. There are optical excitation, electric stimulation, chemical excitation and nuclear energy incentive. The working medium has the metastable energy level which is the dominant position of the stimulated emission, thus realizing the light amplification.

Common component in the laser cavity, the cavity (see) optical resonator is not indispensable part of cavity can make the cavity photons have same frequency, phase and direction, so that the laser has good directivity and coherence. Moreover, it is a good way to shorten the length of the work material, also can be produced by changing the length of cavity to adjust the laser mode (that is, the selected mode), so the general laser cavity.