POLARIZATION STATE SELECTION AND STABILITY IN A LASER WITH A POLARIZATION-ISOTROPIC RESONATOR - AN EXAMPLE OF NO LASING DESPITE INVERSION ABOVE-THRESHOLD

Different models are considered for the study of dynamical instabilities of lasers with a transversally isotropic resonator operating on a single longitudinal mode coupled to a homogeneously broadened J = 1 --> J = 0 material transition. We devise a model of intermediate complexity which retains the dynamics of the atomic variables and which has the experimentally required linearly or circularly polarized steady state solutions with their relative stability near threshold depending on the difference of certain collisionally enhanced relaxation rates. Stability analysis of these steady states in this model provides second thresholds above which the polarization state is time dependent. The stable operation of polarized output states is interpreted in terms of coherence induced absorption or transparency even though the population inversion exceeds the lasing threshold on the transition which drives the orthogonally polarized field, A more general model of the field-atom dynamics than those previously considered is also constructed and analyzed for the stability of its steady states, The fundamental physical condition on the ratio of certain relaxation rates of previous models for stability of circular or linearly polarized solutions unchanged.