Polarization patterns in a nonlinear cavity

An extended field model is applied to study the polarization effects in a nonlinear cavity. This extension leads to a polarization instability that can occur without accompanying optical bistability for a self-defocusing medium. The basic model consists of a nonlinear cavity that is filled with an isotropic nonlinear Kerr medium and driven by a linearly polarized input field. Linear stability analysis of these equations reveals two distinct pattern-forming modes. The first mode (symmetric) maintains the state of polarization of the field and gives rise to hexagonal patterns close to the bifurcation point. The other mode (asymmetric) breaks the polarization symmetry, and this leads to roll formation close to the bifurcation point.