Impact of the vectorial degrees of freedom on the nonlinear behavior of class B lasers

Abstract

A model of a weakly anisotropic (vector) class B single-mode laser operating on the j=1→ j ′=0 ( j is an angular momentum quantum number) homogeneously broadened transition has been presented. It takes into account dynamics of the intersublevel coherence of the upper laser level. The model is suitable for modeling of He–Ne, He–Xe, CO 2, and solid-state lasers. Nonlinear anisotropy of the gain medium in such an isotropic-cavity system favors either linearly or circularly polarized emission, that distinguishes two qualitatively different types of lasers. We have studied in detail, both analytically and numerically, impact of the vectorial degrees of freedom on selection of the polarization states, their stability, mechanisms of their destabilization, and symmetry properties of both types of weakly anisotropic lasers. Dominant role of the vector degrees of freedom in the development of laser instabilities is revealed. Two basic mechanisms of destabilization of the laser states, which are polarization amplitude and polarization phase mechanisms, are analytically distinguished. Among other phenomena our model predicts phenomena of polarization multistability, amplitude polarization chaos, quasiperiodic dynamics with scalar and vector incommensurate relaxation frequencies. Analytical treatment of the problem allowed us to generalize the polarization bad cavity limits to the case of anisotropic-cavity lasers.