Dynamic manifestations of two mechanisms of lasing without inversion in the double-/spl Lambda/ scheme

Summary form only given.It was shown recently that in the double-/spl Lambda/ scheme both cw and self-pulsing regimes can occur, and it is possible to move from one to another regime just by changing the intensity of the driving field or Q factor of the cavity. Although convincing lasing without inversion (LWI) was not achieved, lasing was realized essentially below the conventional threshold and inversionless gain was obtained. It is known that in general two different mechanisms of LWI appear and interfere each other in this scheme. The first mechanism is based on the phenomenon of the coherent population trapping and is connected to an excitation of the low-frequency coherence between two levels of the ground atomic state by bichromatic driving field. The second mechanism represents itself as a kind of resonant anti-Stokes Raman scattering of the driving-field into the lasing field and is associated with the low-frequency coherence induced between two levels of the excited atomic state. The main goal of this paper is to study the role, contribution, and interplay of these two mechanisms into the dynamical behavior of LWI. We study it both analytically and numerically on the basis of the corresponding set of the Maxwell-Bloch equations in the case of resonant driving.