WEAKLY MULTIMODE DYNAMICS OF A PHOTOREFRACTIVE OSCILLATOR

The dynamics of a photorefractive oscillator has been studied in the w eakly multimode case. It is shown that the eigenmodes of the empty cav ity provide the bases in which the transverse patterns of this oscilla tor should be analysed. The concept of mode families i.e. sets of freq uency degenerate modes, is very efficient to classify the different ra nges of operation of the oscillator with Fresnel number up to 5-7. As the complexity of the patterns increases, the interpretation in terms of optical defects or phase singularities greatly simplifies the analy sis.