Wave-front reconstruction by backward-stimulated Raman scattering in a multimode graded-index optical fiber

We have experimentally observed, for the first time to our knowledge, wave-front reconstruction by backward-stimulated Raman scattering (BSRS) in a multimode graded-index fiber. The wave-front reconstruction was quantitatively verified by experiments on beam collimation, intensity distribution, and aberration correction of the BSRS after the beam passed through an aberrator. Polarization experiments also showed that, for a BSRS beam, the sense of circular polarization is nearly identical to that of the incident beam. An interesting aspect of this observation is that, even though the pump excited a large number of modes, the BSRS process appeared to be single-mode-like, and wave-front reconstruction was accomplished.