Abstract

The spatiotemporal dynamics of non degenerate Optical Parametric Oscillators (OPO) in presence of walk-off has been shown to be described by a complex nonstandard Ginzburg- Landau equation. The analysis is carried out for a positive crystal, where the signal and idler are extraordinary beams experiencing walk-off, and the pump is an ordinary beam. It has been shown that the walk-off introduces convective and absolute instabilities, and that it can lower the threshold for signal and idler generation, giving rise to 1D transverse structures instead of bidimensional pattern formation. The emerging transverse signal and idler are travelling waves expanding in the walk-off direction. This predicted behavior is qualitatively similar to that observed in recent experiments on OPOs[1] and in fluid convection[2]. Beyond the threshold, a spatiotemporal analysis allows us to distinguish between convective and absolute structures which can lead, for a certain range of parameters, to noise-sustained or self sustained dynamical structures.

© 1998 IEEE