Coherent Raman spectra and Raman-enhanced self-focusing in multimode fiber

Abstract The spectral and spatial features of the coherent Raman emission (stimulated scattering and/or four-wave mixing) emission from the multimode GeO 2 -doped and P 2 O 5 -doped glass fibers have been studied experimentally. The spectral structures are obviously different for the two kinds of optical fiber samples; however the 10 times reduction of the beam size of the highest-order Stokes SRS component can be observed for both samples due to the Raman self-focusing processes. The refractive index changes induced by the multi-wave mixing with Raman resonance play an important role in these processes.