Singularities of radial gradient perfect vortex beams generated by Pancharatnam-Berry metasurfaces
ORAL
Abstract
Metasurfaces are engineered two-dimensional materials composed of subwavelength-scale nanostructure arrangements that enable precise control over the phase, polarization, and amplitude of light[1,2]. Vortex beams (VBs) are characterized by spiral phase wavefront and carry orbital angular momentum, offering significant potential for applications in optical communications, particle manipulation, and optical imaging[3-5]. Perfect vortex beams (PVBs) maintain a constant radius for their intensity ring, independent of the topological charge, thereby introducing an additional degree of freedom for vortex light control. In this study, we design and fabricate a compact metasurface that facilitates the manipulation of light fields through superposed PVBs, incorporating both sequential integer topological charges (TCs) and gradient numerical apertures (NAs) in the radial direction. This innovative approach successfully generates radial gradient PVBs (RGPVBs) with asymmetric intensity singularity distributions, enabling modulation of singularity positions by varying the initial phase in the metasurface design. Furthermore, we demonstrate arrays of RGPVBs and introduce a novel optical field modulation technique featuring alternating positive and negative TCs. This work brings more possibilities for the superposition of PVB and holds promising applications in singularity optics, information encoding, and particle manipulation.
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