Observation of dynamical eigenmodes induced by the moving refractive index grating of TMI in a rod amplifier

Abstract

We report a novel, to the best of our knowledge, analysis of high power rod fiber amplifiers by monitoring the cross-polarization of the output. Spatially and temporally resolved imaging of co- and cross-polarizations at high power amplification reveals dynamic eigenmode behavior of the rod fiber. The dynamic of the eigenmodes is caused by the moving refractive index grating written by the modal interference pattern of transverse mode instability and is the first direct observation of this refractive index grating, to our knowledge.

Functional Fibers and Functional Fiber-Based Components for High-Power Lasers

“…Beam characterization represented by MD technology and beam quality measurement is an important tool for further study of fiber lasers. The mode information carried by laser beam is the key to understand intrinsic properties and transmission characteristics of HPFLs, which are challenging to be completely analyzed even with complicated measurement methods [489,492,493]. However, it should be noted that the emerging machine learning technology is expected to provide an effective and accurate technical scheme for online analysis [488][489][490][491][492][493][494][495][496].…”