BIFURCATIONS FROM A 8-FOLD ORIENTATIONAL ORDER QUASIPATTERN IN A POLARIZATION INSTABILITY DEVICE

The stability of the 8-fold orientational order quasipattern is studie d both analytically and numerically. Close to the intensity threshold, the sequence, that minimizes the free energy, displays structures bui lt up with four, two and one modes, successively, as the linear refrac tive index decreases. Differently, when increasing the intensity above the threshold, the 8-fold orientational order quasipattern bifurcates to a three mode quasiperiodic pattern, followed by a robust rhombic p attern. A multiconical emission process is invoked to explain the occu rrence of the rhombuses.