Evolution dynamics of discrete-continuous light bullets

We investigate experimentally and numerically the propagation of light bullets (LBs) excited in two-dimensional fiber arrays. The combination of nonlinear self-frequency shift, wavelength dependence of the dispersion and of the inter-waveguide coupling strength induce an adiabatic variation of the parameters of the LBs along their propagation path, until they reach the limits of the regime of existence and decay. The relative strength of the various perturbative effects can be partially controlled by the array’s geometry. The characterization of the LB dynamics is carried out by implementing a spatiotemporal, cross-correlating, spectrally resolved imaging system with femtosecond resolution. The experimental results are in good agreement with the numerical data if higher order nonlinear effects and the wavelength dependence of the dispersion and coupling are included. The observed wavepackets are linked to the stationary solutions of the simplified nonlinear Schrödinger equation. Furthermore the maximum possible range of existence of LBs in arrays of waveguides is discussed.