Near-infrared double-layer cascaded metasurface for beam shaping

The vast applicability of collimated flat-topped beam shapers, predominantly constructed from traditional lens elements, is met with challenges when the scale is less than wavelength. Metasurfaces have an excellent ability for optical manipulation, which can provide a promising approach to flat optics. Here, a metasurface-based Gaussian beam shaper is designed to combine the transmission phase principle with geometric transformation methods, which can reshape a 1550 nm Gaussian beam into a flat-topped beam with a uniformity of 84.39%. Furthermore, a cascaded metasurface beam shaper design is proposed to address the significant divergence in the flat-topped beam obtained from the single-layer metasurface. Simulation results indicate the output beam exhibits both uniform intensity and phase distributions over a considerable transmission distance, effectively minimizing the divergence of the output beam. This research has potential applications in various fields, such as optical antennas, fiber optics, and other optical systems.