Three-dimensional light bullets

Three dimensional light bullets (3D-LB) are the most symmetric solitary waves, being nonlinear wavepackets propagating without diffraction and dispersion. Since their theoretical prediction, the observation of 3D-LB has constituted a long-lasting challenge in nonlinear science, due to the impossibility to avoid catastrophic collapse in homogeneous cubic media. We have recently observed stable 3D-LB in cubic media with periodically modulated transverse refractive index. We found that higher order linear and nonlinear effects force the 3D-LB to evolve along their propagation path and eventually decay. The evolution and decay entails spatiotemporal effects, which under certain conditions, lead to superluminal propagation.