Spatiotemporal chaos in a laser

This paper concentrates on spatiotemporally chaotic regimes. The investigation shows different types of spatiotemporal chaos (extensive and non-extensive) stemming from at least three different origins. The first mechanism is linked to spatial nonuniformities (here the Gaussian lineshape of the laser) that can induce low dimensional spatiotemporal chaos. A second scenario is the interaction between two patterns of different wavenumbers, the pattern with the smallest wavenumber playing the role of spatial nonuniformities for the other pattern. Numerical simulations show that it leads to extensive chaos (linear growth of the number of positive Lyapunov exponents with the size of the system). The third mechanism is a cascade of parametric instabilities: each of the two waves appearing at the primary instability act as a pump for the parametric excitation of two new traveling waves, leading eventually to spatiotemporal chaos.