STIMULATED-EMISSION IN A 3-LEVEL ATOM

We consider light amplification arising from the competition between absorption and stimulated emission of an excitation, which is induced by a monochromatic laser field at low intensities interacting with a three-level atom. The lifetime of the induced excitation 10(5)-10(6) times longer than those of excitations spontaneously emitted. Conditions are established under which the stimulated emission prevails over the induced absorption, and the net negative intensity is 10(2)-10(3) times greater than that of excitations spontaneously emitted, indicating that significant amplification occurs near the frequency of the laser field.