Generation of dynamic and static femtosecond vortex beams and its inscription in low-density polymer

Femtosecond vortex beams with orbital angular momentum were theoretically and experimentally investigated during non-linear inscription in the low-density polymer, poly (methyl pentene). Paraxial mode of vortex beam in the far field is analytically solved by a complex function while the spiral phase front leading to longitudinal field component at high NA was also studied. This work provides the scenario for further investigation of the angular momentum transfer of the spiral light field to the material.