Brijesh Mishra, Brijesh Singh
We propose a numerical method for generating hollow beams using high-order radially polarized modes of the form R-TEM pl , where the radial index p is varied from 1 to 3 while the azimuthal index is fixed at l =1. We used a low-to-high numerical aperture range of focusing lenses in combination with a computer-generated diffractive optical element (DOE) containing multiple alternating opaque and transparent regions. Based on vector diffraction theory, our analysis shows that the multi-zone amplitude mask redistributes the beam energy, thereby leading to the formation of a hollow vector beam. The proposed method provides control over the beam width, maintaining a uniform dark-core size after focusing through various NA lenses across all higher-order vector modes. Further, the width of the high-intensity ring can be tuned by varying the NA of the focusing lens. Furthermore, we study the evolution of the generated high-order hollow vector modes during near-field-free-space propagation. We envisage that the generated hollow vector beam may be useful for particle manipulations, especially for trapping metallic particles with reduced thermal effects, ring-shaped ablation, and optical microscopy.