PATTERN-FORMATION AND COMPETITION IN NONLINEAR OPTICS

Recently we have observed two-dimensional periodic and quasiperiodic s tructures in the transverse profile of an optical beam circulating in a feedback loop which contains a The symmetries observed depend not on ly on the interaction between light and nonlinear medium, but also on a nonlocality due to beam rotation in tile feedback loop. The linear s tability analysis of our model shows the existence of many unstable ba nds of transverse wavevectors. Close to threshold, predictions are qua litatively and quantitatively confirmed by the experiment. When the in tensity threshold values are almost the same for the two principal ban ds, structures with different wavenumbers arise above threshold. These modes compete with a very complex dynamics. We have started to study this behavior by means of suitable indicators. As a first indicator ir e have individuated the fraction of light power distributed on tile fi rst band respect to that one distributed oil both.