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.

Three-Dimensional Trapping and Manipulation of a Mie Particle by Hybrid Acoustic Focused Petal Beams

“…Figure 2 and 2(a4) represent the acoustic intensity and phase profiles on three focal planes of z = 12λ, z = 8λ, and z = 4λ, respectively. At z = f 1 = 8λ, four petal-like bright spots are observed in the intensity distribution, and the phase profile is divided into four sections with an adjacent jump of π [34,40]. At the same time, two bright spots appear at two focal points of (0, 0, 12λ) and (0, 0, 4λ).…”

“…The M -arm anticlockwise FSS can generate a focused acoustic vortex (FAV) with a TC of l = M, and the M -arm clockwise FSS produces a FAV with a TC of l = −M [38]. When an acoustic plane wave with a wavelength of λ transmits through this combined FSS, two FAVs with opposite TCs of l = ±M are generated simultaneously, and the interaction between them results in a focused acoustic petal-like beam (FAPB) with 2M petals [39,40]. Here, the width of the slit is fixed at d = λ/2 and the focal length is set as f 1 .…”