Kerr self-cleaning of femtosecond-pulsed beams in graded-index multimode fiber

TLDR

The self‑cleaning of femtosecond pulses in graded‑index multimode fiber could benefit ultrafast pulse generation and beam‑combining. The experiment launches 80‑fs, 1030‑nm pulses into a 62.5‑µm core graded‑index multimode fiber, where Kerr nonlinearity drives the self‑cleaning. The 80‑fs pulses self‑clean, transforming a speckled output into a bell‑shaped beam as pulse energy rises, a behavior reproduced by Kerr‑based numerical simulations.

Abstract

We observe a nonlinear spatial self-cleaning process for femtosecond pulses in graded-index (GRIN) multimode fiber (MMF). Pulses with ∼80 fs duration at 1030 nm are launched into GRIN MMF with 62.5 μm core. The near-field beam profile at the output end of the fiber evolves from a speckled pattern to a centered, bell-shaped transverse structure with increasing pulse energy. The experimental observations agree well with numerical simulations, which show that the Kerr nonlinearity underlies the process. This self-cleaning process may find applications in ultrafast pulse generation and beam-combining.