Bend Distortion Effect on Transverse Mode Instability

Transverse mode instability (TMI) limits the power scaling of high-power fiber lasers and amplifiers. One method of mitigating TMI is to strip unwanted modes by bending the fiber. However, the bending-induced mode distortion will change the TMI coefficient and influences the TMI threshold. In this work, we analyzed the bending effects on the mode profiles by inducing different refractive index tilts corresponding to different bending radii. With these mode profiles and with different bending conditions, a modified TMI coefficient was calculated to analyze the bending effects on TMI for different fibers. The simulation results show that tighter bending can lead to a somewhat lower TMI coefficient and slightly improve the TMI threshold.