Beam cleanup of a multimode fiber seeded by an off-center single-mode laser source

We study the beam cleanup of a multimode (MM) fiber with different output energy pattern following injection from a single-mode fiber laser source. The experimental research is based on a stochastic parallel gradient descent (SPGD) algorithm. The output beam intensity profile from the MM fiber varies via the change of the offset when the input single mode fiber spliced to the MM fiber. This is a consequence of diverse high-order modes excited in the MM fiber where the off-center single mode laser inject into. The experiment system is setup by using phase only liquid crystal spatial light modulators (LC-SLM). It is shown that the beam cleanup of the multimode fiber is depressed when the offset are relative large.