Spatial Beam Self-Cleaning and Supercontinuum Generation with Yb-doped Multimode Graded-Index Fiber Taper Based on Accelerating Self-Imaging and Dissipative Landscape

TL;DR

This paper demonstrates how tapered Yb-doped multimode fibers can achieve spatial beam self-cleaning and supercontinuum generation through nonlinear effects and dissipative dynamics, enabling broad-spectrum light sources.

Contribution

It introduces a novel experimental setup combining tapered multimode fibers with active gain to achieve simultaneous beam self-cleaning and supercontinuum generation.

Findings

Beam self-cleaning occurs above 20 kW peak power.

Supercontinuum spans 520-2600 nm in active fibers.

Dissipative landscape causes modal transitions along the taper.

Abstract

We experimentally demonstrate spatial beam self-cleaning and supercontinuum generation in a tapered Ytterbium-doped multimode optical fiber with parabolic core refractive index and doping profile when 1064 nm pulsed beams propagate from wider (120 micrometers) into smaller (40 micrometers) diameter. In the passive mode, increasing the input beam peak power above 20 kW leads to a bell-shaped output beam profile. In the active configuration, gain from the pump laser diode permits to combine beam self-cleaning with supercontinuum generation between 520-2600 nm. By taper cut-back, we observed that the dissipative landscape i.e., a non-monotonic variation of the average beam power along the MMF leads to modal transitions of self-cleaned beams along the taper length.