Propagation of partially coherent vortex beams in gain media

In this paper, the propagation of partially coherent vortex beams in gain media was investigated based on the generalized Huygens-Fresnel principle. Our research focused on the influences of topological charge (m) and coherence length (σ0) on light intensity distribution, phase and spectral degree of coherence during the propagation. The results show that partially coherent vortex beams can maintain their initial dark hollow intensity distributions for a longer distance with larger m and σ0 as the gain and diffraction effects appear simultaneously. The decay of the maximum value of light intensity caused by diffraction is more obvious with a smaller σ0. On the other hand, the larger σ0 is, the more obvious the gain effect on the maximum value of light intensity is. We also observe that the coherence vortex with topological charge equals to m will split into m coherence vortices with topological charges are 1, and the coherence vortices with negative topological charge will generate at the same time. Some phenomena also appear with a larger coherence length, for example, a larger distance between coherence vortices with negative topological charge, a bigger splitting of the coherence vortices, and a slower damping of spectral degree of coherence, et al. This study can be used in the research and application of vortex beams in the materials field.