Polarization Effects on Thermal-Induced Mode Instabilities in High Power Fiber Lasers

TL;DR

This study investigates how polarization influences thermal-induced mode instabilities in high-power fiber lasers, combining theoretical modeling and experimental validation to determine the MI threshold power.

Contribution

It provides a comprehensive theoretical model considering polarization effects and experimentally confirms that polarization characteristics do not affect the MI threshold in fiber lasers.

Findings

Polarization has no impact on MI threshold.

Experimental MI threshold measured around 367-386W.

Theoretical and experimental results show good agreement.

Abstract

We present detailed studies of the effect of polarization on thermal-induced mode instability (MI) in ytterbium-doped fiber amplifiers. Based on a steady-state theoretical model, which takes both electric fields along the two principal axes into consideration, the effect of polarization effects on the gain of Stokes wave was analyzed, which shows that the polarization characteristics of the fiber laser have no impact on the threshold of MI. Experimental validation of the theoretical analysis is presented with experimental results agreeing well with the theoretical results, in which polarization-maintained and non-polarization-maintained fiber lasers with core/inner cladding diameter of 30/250um and core NA of 0.07 were employed. The MI threshold power is measured to be about 367~386W.