Propagation characteristics of nonparaxial Gaussian beams

Based on the rigorous definition of light intensity of nonparaxial vectorial beams in the transverse plane, beam width, far-field divergence angles and M2 factors are defined by the power in the bucket. Taking nonparaxial vectorial Gaussian beam as an example, the detailed theoretical analyses and numerical calculations about the propagation characteristics are performed, and the results are compared with those from the nonparaxial scalar theory. Showing that when the half width of light source ω0 is less than Λ, there are obvious differences between the propagation characteristics described by the nonparaxial scalar and the vectorial theory, and their propagation characteristics tend to be consistent with ω0 increasing, change to that obtained in the paraxial scalar approximation gradually.