Abstract
Nonlocal engineering, as an extension of the local design of the metasurface, provides a new scheme to precisely tune the electromagnetic response through diffraction of the constitutive supercells. It has shown great potential in large-gradient wavefront shaping, but just limited to one-dimensional or rotation-symmetric two-dimensional applications. In this study, we extend the nonlocal method to design large-gradient metasurfaces without rotation symmetry, through the optimization of the metagratings and their deformation along the isophase contour path. The effectiveness of the method is verified by the three-foci metalenses with NA of 0.89 and NA of 0.97. Consistent simulation and experimental results are obtained at 140 GHz. Obvious advances are observed in this method especially when the spatial phase gradient is increased.
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