Composite spiral multi-value zone plates.

Abstract

We present composite spiral multi-value phase zone plates that are achieved by sectioning a spiral multi-value phase zone plate into several radial regions. Each region is composed of specially structured Fresnel zones with optimized phase values and an embedded basic topological charge. In numerical studies, it is shown that the proposed element is capable of producing equal intensity arrays of petal-like modes as well as dark optical ring lattice structures along the optical axis in multiple focal planes of the diffractive element. Additionally, it is demonstrated that the generated petal-like modes can be rotated in a controllable manner by implementing an angular frequency shift between the two composited spiral multi-value phase zone plates. We also illustrate that the rotation angle is independent of the diffraction order. Experimental results are included to verify the theoretical outcomes, where the phase pattern of the composite spiral multi-value zone plate is encoded onto a spatial light modulator.