Schemes and methods for creating inversion. Kinetic equations

To obtain induced radiation, various forms of energy conversion into energy of induced radiation are used. It is necessary that t> t _N.

If it turns out that m _H > m, then there will be a stationary mode, that is, a pulsed excitation.   Kinetic equations allow us to investigate the dependence of the population in time and on the pump equation. And this ultimately allows to determine the required threshold level of pumping.

Kinetic equations for a three-level system.

Such a system is characteristic for the excitation of ruby. v _OH for ruby ​​in the green area.

With ,

In the presence of a weak field, a three-level system has positive energy, that is, it can be excited if, in the limit, half of the active particles can be excited.

A four-level system is easily excited.