Beam self-cleaning beyond its current understanding

ongoing

The goal of BESCLING is to shed light on the physics of the beam self-cleaning (BSC) effect. This is driven by Kerr nonlinearity and consists of the spontaneous increase of the spatial quality of a multimode beam, which turns from speckles in the linear regime to a bell shape at sufficiently high power. Since its first observation, BSC has attracted great interest, mostly because it allows for improving the performances of state-of-the-art optical fibre technologies; remarkable examples are the power scale-up of fibre lasers and the resolution enhancement of multiphoton imaging devices. Despite these successes, the physical mechanisms behind BSC are still largely debated. Specifically, recent experiments demonstrated that for achieving BSC the temporal beam evolution plays a pivotal role. Whereas the temporal dimension has been often ignored in the investigation of BSC. Here, I propose a new approach to dig into the physics of BSC. I will build up a holographic mode decomposition tool, which, in addition to retrieving the mode occupation at the fibre output, allows for obtaining information on the beam temporal profile. This will pave the way to a fully spatiotemporal interpretation of BSC, e.g., it will enable the understanding of the simultaneous occurrence of BSC and supercontinuum generation, whose physical interpretation has been largely disregarded, so far. In addition, to survey the generality of BSC, I will explore photonics platforms beyond standard multimode optical fibres like few-mode optical fibres and lossy fibres made of soft glass or polymer. To date, theoretical models do not apply to these types of systems and, from the experimental point of view, only a few observations of BSC have been reported. To this goal, the Laboratoire Interdisciplinaire Carnot de Bourgogne is the perfect Host Institution since it is the only laboratory in Europe that combines expertise in all aspects of BESCLING, from nonlinear guided optics to special fibre fabrication.