Diffraction by a radial phase modulated spiral zone plate of abruptly autofocusing beams generated with multiple Bessel-like beams

In this paper, we present the generation of optical vortices using an abruptly autofocusing beam that is combined from multiple Bessel-like beams, diffracted by a radial phase shift modulated spiral zone plate (RSSZP). The analytical formula for the diffracted wave field amplitude of the produced beam is derived based on the Fresnel diffraction integral formula. The results show that the intensity distributions of the produced output beam in radial direction are determined by the initial beam parameters and the RSSZP parameters, such as shifting parameter and topological charge. The present work gives also the diffraction by a RSSZP of a fundamental Gaussian beam which is deduced as a particular case in this investigation.