NONLINEAR-THEORY OF NONINVERSION LASERS OF AN OPEN 3-LEVEL SYSTEM

A nonlinear theory of a noninversion laser of an open three-level syst em based on electromagnetically induced transparency is given. In this noninversion laser model, a nonselective pumping mechanism is used fo r obtaining lasing gain such that the population in the lower lasing l evel is always larger than a half of the total population no matter wh ether the driving held is on or off. In the lasing region, there is no direct pumping to the upper level. The conditions for the existence o f a nontrivial and stable laser field are obtained. The dependence of the laser intensity on the intensity of the driving field and the rati o of the two decay rates from the upper level has been obtained, and t he ways to obtain a large laser field have been studied.