Extension of Vortex Bessel Beams Generated by Finite-Width Durnin Ring With Helical Phase Modulation

Bessel beams are widely used for different applications due to their attractive non-diffractive behavior. However, the real-world Bessel beams have finite propagation distance, where such behavior can be assumed. In this work we consider the degradation of vortex Bessel beams generated by a finite-width Durnin ring with helical phase modulation. For this purpose, we derive the expression that describes the propagation of rotationally symmetric vortex beams. By using this expression, we show that the axial degradation of the main lobe of Bessel beams is almost independent on their topological charge and decreases by increasing the radius of the Durnin ring and its width. The increase of ring width also yields to the radial degradation (deformation of the secondary lobes) of the Bessel beams. These findings are particularly important for the construction of more sophisticated structured beams described as a linear superposition of vortex Bessel beams.