BEAMLOCKER - Beam self-cleaning for spatiotemporal mode-locked fiber lasers 

ID Call: HORIZON-MSCA-2021-PF-01 MSCA Postdoctoral Fellowships

Sapienza's role in the project: Host Institution

Supervisor: Stefan Wabnitz

Fellow: Yifan Sun

Dipartimento: Information Engineering, Electronics and Telecommunications

Project start date: June 1, 2022

Project end date: May 31, 2024

Abstract:

Mode locking (ML) stands as a pivotal technique for generating ultrashort laser pulses, driving remarkable advances in harnessing longitudinal modes within lasers characterised by a single transverse mode, exemplified by single-mode fibre lasers. The advent of spatiotemporal mode-locking (STML) has revolutionised this landscape by locking both transverse and longitudinal modes in multimode fibre (MMF) lasers to produce ultrafast spatiotemporal pulses. This innovation has opened new avenues in studies of nonlinear wave propagation. The intrinsic multimodal nature of these lasers empowers them to deliver higher-power pulses compared to their single-mode counterparts. Nonetheless, the interplay between transverse modes poses a challenge to achieving high spatial beam quality. A potential solution arises through spatial beam self-cleaning in graded-index MMF. As the pulse power surges past a certain threshold, Kerr nonlinearity introduces a transformative process that effectively redirects power from higher-order modes into the fundamental mode, leading to a stable and robust bell-shaped output transverse profile. Within this context, the BEAMLOCKER project delves into the dynamics of STML MMF lasers, with the primary objective of attaining high-quality output beams through physical modellings. The investigation will span across analytical methodologies, direct numerical simulations, and numerical continuation and bifurcation techniques. The outcome of this endeavour may ignite a wave of further theoretical investigations and experimental undertakings in the realm of interactions within nonlinear multimode fibre systems.