Designing advanced very-large-mode-area fibers for power scaling of fiber-laser systems

TLDR

Fiber lasers offer high efficiency, beam quality, and thermal management, yet their high‑power performance is limited by nonlinear effects that can be mitigated by enlarging the mode‑field area, though this makes maintaining single‑mode operation increasingly difficult. This study examines the demands and challenges involved in designing very‑large‑mode‑area fibers. The authors highlight higher‑order mode delocalization as the working principle of active double‑clad VLMA fibers. They propose and analyze a new low‑symmetry large‑pitch fiber that improves state‑of‑the‑art fiber‑laser performance by enhancing higher‑order mode delocalization.

Abstract

Fiber lasers are a highly regarded solid-state laser concept due to their high efficiency, beam quality, and easy thermal management. Unfortunately, the performance of high-power fiber-laser systems is challenged by the onset of detrimental nonlinear effects. Their impact can be reduced dramatically by employing fibers with larger mode-field areas. Even though this is an efficient way to mitigate nonlinear effects, maintaining effective single-mode operation, and with it high beam quality, becomes increasingly difficult as the core is enlarged. In this paper the demands and challenges for the design of a very-large-mode-area (VLMA) fiber are discussed. The benefits of using higher-order mode delocalization as the working principle of active double-clad VLMA fibers are described. Finally, a new low-symmetry large-pitch fiber, which is expected to improve the performance of state-of-the-art fiber-laser systems by increasing higher-order mode delocalization, is proposed and thoroughly analyzed.