Rogue waves in the beam profiles of multifilaments

Here we discuss a second optical system that clearly features rogue waves, namely the spatial fluence distribution in multifilament beam profiles. Given the formal analogy between one-dimensional fiber solitons and the spatial two-dimensional filament strings, the appearance of rogue waves may not appear overly surprising at first sight. We will show, however, that there are marked differences in the driver mechanism between both optical systems. In particular, while shot-to-shot energy fluctuations on the input beam are considered the driver for rogue wave dynamics in fibers, the formal equivalent of shot-to-shot beam profile variations does not seem to play any role in our system. Instead, mechanical turbulence inside the filament cell appears to act as the trigger mechanism. Refractive index fluctuations inside the cell then act to steer individual filaments into each other, which gives rise to short lived mergers. These filament mergers constitute the rogue waves in our two-dimensional system.