Semiclassical theory of dye lasers: the single-frequency and multifrequency steady states of operation

A semiclassical theory of dye lasers is presented in which the relevant energy-level diagram of a dye molecule is assumed to consist of a bandlike ground state with many sublevels and an excited single state. This theory not only describes the single-frequency operation, which has a low instability threshold, but also describes the two-frequency and multifrequency steady states of operation and the transitions between the different steady states. The general solution of a multifrequency operation is given explicitly and differs essentially from the well-known Rabi oscillation. The theoretical predictions are in good agreement with recent experiments done by Hillman et al., [ Phys. Rev. Lett.52, 1605 ( 1984)], which cannot be explained by the conventional Maxwell–Bloch laser theory derived from two-level atoms.