Optical rogue waves in the solid-state laser with a saturable absorber

We study the features of the optical rogue waves (ORW) observed in an all-solid-state (diode-pumped, Cr:YAG+Nd:YVO₄) passively-Q-switched laser, which is a system of wide practical interest. The extreme events appear during the chaotic and hyper-chaotic regimes of this laser, in one of two forms: 1) as isolated pulses of large intensity (“Intensity ORW”) or: 2) as a long time between pulses (“Time ORW”). These two types of extreme events are not correlated (i.e., an I-ORW is not always preceded or followed by a T-ORW). The standard theoretical description of this laser system (three-level rate equations for a single mode of the field and a two-level system for the absorber) is not able to predict these phenomena, not even the mere existence of ORW. Faced with the problem of improving the theoretical description, we find that ORW are observed if the Fresnel number of the laser cavity and the embedding dimension of the attractor reconstructed from the experimental time series are high, and the laser spot profile presents a spatially complex structure. These results suggest that the spatial effects are an essential ingredient in the formation of ORW in this type of lasers.