A simple model of a laser without inversion

摘要: Abstract We consider a simple model of four level atom as candidate for laser action without population inversion. Our system has degenerate or quasi-degenerate ground state doublet and two higher excited states; one these levels is coupled to the states by coherent field variable strength, whose role create atomic coherence between lowest levels; other also but only when develops. This includes an incoherent pump mechanism produce some in top lasing state. calculate absorption profile transition identify conditions under which gain may develop. find that available over suitable range values driving strength rates. The shape frequency at maximum change varies operating conditions. provide physical interpretation our results with help convenient set dressed states.