Modal energy transfer by thermally induced refractive index gratings in Yb-doped fibers.

ABSTRACT: Thermally induced refractive index gratings in Yb-doped fibers lead to transverse mode instability (TMI) above an average power threshold, which represents a severe problem for many applications. To obtain a deeper understanding of TMI, the evolution of the strength of the thermally induced refractive index grating with the average output power in a fiber amplifier is experimentally investigated for the first time. This investigation is performed by introducing a phase shift between the refractive index grating and modal interference pattern, which is obtained by applying a pump power variation to the fiber amplifier. It is demonstrated that the refractive index grating is sufficiently strong to enable modal energy coupling at powers that are significantly below the TMI threshold if the in

SUBMITTER: Stihler C 

PROVIDER: S-EPMC6123421 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature