Two-dimensional solitary pulses in driven diffractive-diffusive complex Ginzburg-Landau equations

Two models of driven optical cavities, based on two-dimensional (2 D) Ginzburg-Landau equations, are introduced. The models include loss, the Kerr nonlinearity, diffraction in one transverse direction, and a combination of diffusion and dispersion in the other one (which is, actually, a temporal direction). Each model is driven either parametrically or directly by an external field. By means of direct simulations, stable completely localized pulses are found (in the directly driven model, they are built on top of a nonzero flat background). These solitary pulses correspond to spatiotemporal solitons ("light bullets") in the optical cavities. Basic results are presented in a compact form as stability regions in a full three-dimensional (3 D) parameter space of either model. The stability region is bounded by two surfaces; beyond the left one, any 2 D pulse decays to zero, while quasi-1D pulses, representing spatial solitons in the optical cavity, are found beyond the right boundary. The spatial solitons are found to be stable both inside the stability region of the 2 D pulses (hence, bistability takes place in this region in the two models) and beyond the right boundary of this region (although they are not stable everywhere). Unlike the spatial solitons, their quasi-1 D counterparts in the form of purely temporal solitons are always subject to modulational instability, which splits them into an array of 2 D pulses. A uniform nonzero state in the parametrically driven model is also modulationally unstable, which leads to formation of many 2 D pulses that subsequently merge into few ones in a certain parameter region.