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Extreme events are characterized by rare and high amplitude excursions of a given variable characterizing a physical system with respect to its long time average. Its study in optics has been primarily motivated by the analogy with rogue waves in hydrodynamics and includes ingredients such as spatial instabilities, nonlinearities and noise.
Here we consider a spatially extended microcavity laser with integrated saturable absorber in the self-pulsing regime. This system, thanks to its short typical timescales, allows large recordings and accurate statistics. Moreover, it does not display irregular or aperiodic dynamics without spatial coupling. Hence, the role of spatial coupling in the emergence of extreme events can be studied. With the help of a model and of numerical analysis together with the experimental observations, we unveil the dynamical origin of the extreme events in the occurrence of spatiotemporal chaos [1], rather than through collisions of coherent structures. Moreover, by investigating the fine structure of the maximum Lyapunov exponent, of the Lyapunov spectrum and of the Kaplan-Yorke dimension of the chaotic attractor, we are able to deduce that intermittency plays a key role in the proportion of extreme events measured. We assign the observed mechanism of generation of extreme events to quasi-periodic extended spatiotemporal intermittency [2]. The understanding of the formation mechanism of these extreme phenomena is an important step to devise strategies to control them.
[1] Selmi et al, Phy. Rev. Lett. 116, 013901 (2016).
[2] Coulibaly et al, Phys. Rev. A 95, 023816 (2017).
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