SPATIOTEMPORAL DYNAMICS OF OPTICAL PARAMETRIC OSCILLATORS

The coupling of diffraction and the chi(2) nonlinearity is shown to le ad to pattern formation in parametric oscillators in optical cavities. In particular the threshold for the generation of signal and idler wa ves is lowered by an off-axis emission for negative detunings. The out put intensity is spatially modulated just above threshold while more c omplicated patterns appear for larger values of the pump amplitude. Co mpetition between domains of rolls with different orientations leads t o long transients until boundary effects prevail. In the case of finit e-size input beams, the roll orientation is locally perpendicular to t he boundary and the pattern tends to rotate. Finally, the effect of sp atial structures on the spectrum of quantum fluctuations of the vacuum is considered and discussed.