Optical rogue waves - A study of extreme events in photonics

Rogue waves are rare phenomena of extreme intensity, and for decades they have aroused great interest in both the scientific and maritime communities. The mechanisms behind their formation are still the subject of debate, mainly due to the complexity of making relevant experimental measurements on the scales involved. However, the study of so-called "extreme" events, linked to particular statistics, is not confined to the field of hydrodynamics, and has a considerable, even dramatic, impact on many areas of the physical and social sciences. The field of photonics, and mainly guided optics, is particularly well suited to the study of these extreme phenomena, as there are many mathematical equivalences between wave propagation on the ocean surface and that of light pulses in optical fibers, in which comparable physical mechanisms are at work. The study of these events in photonics, because of its similarities with hydrodynamics, but also for a better understanding of the underlying fundamental processes, has been of great interest to the scientific community for some fifteen years.

The aim of this article is to give an overview, obviously not exhaustive, of the processes leading to the occurrence of scelar events in photonics, with particular emphasis on the guided propagation of ultrashort pulses and the unstable phenomena inherent in them. First, the tools needed to approach and understand extreme events from a statistical point of view are introduced, enabling us to define the criteria for determining whether or not they are present in a system. Then, after a few essential reminders of the linear and non-linear propagation of light pulses, optical freeze waves are detailed in different contexts (optical fibers, lasers, free-space systems) and put into perspective, highlighting the limitations of the optical-hydrodynamic analogy. Finally, the critical and essential point of capturing and experimentally characterizing these phenomena is addressed. The main technological solutions (ultra-fast measurement techniques) used today to characterize events that are by definition non-reproducible are outlined. Bibliographical references are also provided for readers wishing to delve deeper into this extremely rich and constantly evolving subject.