Generating Composite Vortex Beams with Single-Helicity Annulus-Sector Spiral Zone Plates

Composite vortex beams (CVBs) with multiple spatial singularities and orbital angular momentum (OAM) are widely used in various applications including multiple optical traps and optical communication. Here, based on the equal-angle segmentation and radial displacement modulation approach, we propose an innovative scheme for generating CVBs with controllable OAM spectrum by proposing a simple and compact optical element termed as single-helicity annulus-sector spiral zone plates (SASZPs). Theoretical analysis reveals that by modulating the structural parameters of the SASZPs, such as the topological charge, the radial misalignment parameter and the number of annulus-sector primitives, an attractive intensity pattern consisting of petal-like structures can not only be produced but also the mode purity of CVBs can also be flexibly controlled. In addition, by adopting the high-quality and low-defect diamond substrate we have synthesized, based on the electron beam lithography technology and dry etching technology, the SASZP samples with different parameters have been fabricated and the focusing properties of such optics in the visible light region have been carried out and verified. These findings direct a new avenue for improving the performance of ultra-compact solar-blind UV imaging, optical communication and integrated optics.