The thermal grating (TG) and inversion grating (IG) TMI gain dependence on the light beating intensity spectrum is investigated. TMI gain is restricted to intensity bandwidths comparable to the thermal gain bandwidth of ∼20 kHz. Seed laser phase noise generates intensity spectra determined by the laser linewidth and the relative group delay time of the gain fiber. These spectral bandwidths exceed the thermal gain bandwidth by orders of magnitude in both the coherent and incoherent regimes, making them unlikely sources of TMI. It is suggested that phase noise generated in the gain fiber due to external perturbations may be the source of the TMI.
ACCESS THE FULL ARTICLE
Marc D. Mermelstein, "Laser linewidth dependence to the transverse mode instability (TMI) nonlinear gain in kW-class fiber amplifiers (Erratum)," Proc. SPIE 10512, Fiber Lasers XV: Technology and Systems, 1051221 (26 February 2018);