Focused, evanescent, hollow, and collimated beams formed by microaxicons with different conical angles

Diffraction patterns formed by axicons with different tip (vertex) angles are analytically and numerically investigated. Results show that the axicon (or tapered dielectric probe) can form an extended axial light beam, a compact evanescent field, a hollow beam, and a collimated beam, depending on the vertex angle. Two-dimensional and three-dimensional models of a tapered dielectric probe show that, with small changes to the vertex angle, light transmitted by the probe is scattered rather than focused, and vice versa. Angle meanings corresponded to boundary transitions have a quantum character and densify as the angle approaches zero. These features should be taken into consideration when manufacturing microaxicons intended for various applications.