Diffraction of plane waves by apodized finite-radius spiral phase plates of integer and fractional topological charge

Abstract

An analysis of the diffraction of plane waves by an apodized finite-radius circular spiral phase plate (SPP) with integer and fractional topological charge and with variable transmission coefficients inside and outside of the plate edge is presented. We introduce a sinusoidal apodization function at the edge of the plate to allow for a continuous transition between the transmission coefficients, and between the spiral and uniform phase distributions inside and outside of the plate edge. The interference between the light crossing the SPP and the light which undergoes no phase alteration at the aperture plane, and the presence of an apodization at the edge of the plate, cause some interesting phenomena previously unobserved in this widely known problem.