Abstract

The Brillouin fiber ring laser is usually a system in which the state of polarization of the optical beams remains linear. This is commonly achieved by the use of a polarization maintaining fiber inserted into an appropriate ring structure. If the fiber is sufficiently short, the first order Stokes emission remains stable and monomode whatever the input pump power may be. However recent experiments have shown that this situation becomes drastically different if the ring structure is shghtly modified in such a way that the state of polarization of the optical waves changes all along the fiber (ref. ¹). The laser then exhibits polarization instabihties which can be studied by a decomposition of the Stokes field along two eigendirections characterizing the system. An antiphase phenomenon has then been observed for periodic and quasiperiodic regimes. Such a dynamical behavior cannot be interpreted within the framework of the usual three-wave model which assumes that both the pump and Stokes fields remain linearly polarized. By considering that the optical fields can propagate into the two orthogonally polarized modes of the fiber, we have modified the three-wave model in order to understand in what way the polarization of the Ught beams may influence the laser behavior. The system dynamics has been studied by the aid of numerical simulations that have revealed dynamical behaviors similar to the experimentally observed one.

© 1998 IEEE