Filamentation of Femtosecond Vector Beams

We numerically study the filamentation of femtosecond vector beams with spatially varying polarization profiles in air. The vector beams include azimuthal, radial, and spiral cylindrical vector beams (CVBs), as well as low-order Full Poincar\'e beams (FPBs) with star and lemon polarization topologies. Comparing the filamentation of CVBs to that of a circularly polarized Laguerre-Gaussian (LG) beam, we found that CVBs undergo filamentation more easily due to their more effective nonlinear focusing, in contrast to the LG beam. In the case of low-order FPBs, we examined the role of the constituent orthogonally polarized spatial modes in their filamentation process. Our findings revealed that the Gaussian mode within these beams primarily contributes to their filamentation. Additionally, when compared to a linearly polarized Gaussian beam, star and lemon FPBs displayed greater resistance to filamentation. Furthermore, we investigated the evolution of polarization profiles of the beams during filamentation. We observed that the polarization profiles of CVBs remained largely unchanged. In contrast, the polarization profiles of the FPBs underwent significant non-uniform changes due to differences in accumulated nonlinear phase and Gouy phase among the constituent modes.