3D simulation of focusing a laser beam by a dielectric conical microaxicon

In this work, using a finite element method implemented we simulate in the Comsol software focusing a TE-polarized Gaussian beam by 3D dielectric conical microaxicon tapers with smaller-than-30-degrees vertex angles. The simulation results have shown that, as is the case with the 2D axicons, with minor changes in a vertex angle, the 3D axicon can alternatively show either focusing or defocusing properties. However, the angle intervals in which the 2D and 3D axicons show focusing or defocusing properties are different.