ROLE OF SYMMETRIES IN THE TRANSITION TO TURBULENCE IN OPTICS

Spatiotemporal dynamics of patterns of the light beam emitted by a pho torefractive oscillator has been investigated in the case of very larg e transverse dimensions. Time and space averagings show that the trans ition to turbulence as transverse dimensions are increased is a two-st ep process. Symmetry properties of the average patterns reveal that af ter the first transition from a boundary-to a bulk-dominated behavior already observed at Fresnel numbers N-F similar or equal to 20 there i s a second transition around N-F similar or equal to 100 The regime co rresponds to a complete loss of symmetry and appears here as soon as t he correlation length of the patterns becomes of the same size as the period of the optical grating in the gain medium. [S1050-2947(98)01601 -1].