Eckhaus instabilities induced by nonuniformities: a laser example

Summary form only given. Stable spatial structure such as stationary waves are expected to appear in a range of optical systems. However, the study of such waves in hydrodynamics revealed that spatial variations of control parameters can lead to instabilities that cannot, be predicted using the uniform medium approximation. Since nonuniformities are very common in optics (e.g., Gaussian pump profile, line shapes, curvature of mirrors...), it is important to know if this type of instability can also affect optical systems. Here we show how this instability affects parametric waves with one spatial dimension. The experimental orientations are performed on a modulated multimode fiber laser (displaying spectral waves), that is described by classical amplitude equations for parametric interaction.