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 instabiliti es of lasers with a transversally isotropic resonator operating on a s ingle longitudinal mode coupled to a homogeneously broadened J = 1 --> J = 0 material transition. We devise a model of intermediate complexi ty which retains the dynamics of the atomic variables and which has th e experimentally required linearly or circularly polarized steady stat e solutions with their relative stability near threshold depending on the difference of certain collisionally enhanced relaxation rates. Sta bility analysis of these steady states in this model provides second t hresholds above which the polarization state is time dependent. The st able operation of polarized output states is interpreted in terms of c oherence 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-a tom dynamics than those previously considered is also constructed and analyzed for the stability of its steady states, The fundamental physi cal condition on the ratio of certain relaxation rates of previous mod els for stability of circular or linearly polarized solutions unchange d.