Generating multi-focus circular beams via all-dielectric metasurfaces

Abstract The multi-focus circular beams (MFCBs), a special class of optical beams capable of multiple autofocusing events, hold significant potential for multi-particle manipulation and optical tweezers. In this work, we propose an all-dielectric metasurface design that leverages joint amplitude and phase modulation to generate MFCBs, integrating both Pancharatnam-Berry (PB) geometric phase and propagation phase control. By precisely engineering the transmission coefficient and phase profiles of meta-atoms, we achieve dynamic tuning of the focus number and the focal depth through tailored parameter adjustments. Furthermore, by incorporating rotational phase modulation, we extend this approach to construct metasurfaces capable of generating two-dimensional beam arrays, demonstrating the versatility of co-modulated amplitude and phase in structured light manipulation.