Two-level description of instabilities in nonlinear fabry-perot cavities

The intracavity absorption (or gain) coefficient of two-level atoms embedded inside a Fabry-Perot cavity has been demonstrated to be well represented by an equivalent two-level system. The parameters of this new two-level system are simply related to that of the medium and to the cavity characteristics. When associated with well- known results of fluorescence spectra and nearly degenerate four-wave mixing in two-level media, this equivalence provides a universal description of intracavity resonance fluorescence and relaxation oscillations in any nonlinear absorptive, amplifying, or dispersive Fabry-Perot cavities.