Extreme Events related with spatial patterns in an all-solid-state laser with saturable absorber
The passively Q-switched, self-pulsing all-solid-state laser is a device of widespread use in many applications. Depending on the condition of saturation, which is easy to adjust, different dynamical phenomena are observed: continuous wave emission, stable oscillations, period doubling bifurcations, chaos and, in some chaotic regimes, extreme events in the form of pulses of extraordinary intensity. These pulses are also sometimes called "dissipative optical rogue waves". The mechanism of their formation is still unknown. Here, we report the direct observation of the pulse-to-pulse evolution of the transverse pattern with an ultrafast camera (up to 60,000 frames per second). A specific pattern is correlated with the pulse intensity in the periodical regimes. In the chaotic regimes, the extreme events are correlated with some patterns. The series of patterns before and after an extreme event are often the same. These observations demonstrate that extreme events in this system are the consequence of the deterministic nonlinear interaction of few modes. This information plays a crucial role in the development of a theoretical model able to describe the mechanism giving raise to extreme events. The model is expected to lead to the control of their formation at will, what is of practical interest.