A kind of polar coordinate system adaptable metasurface and its broadband wavefront manipulation

Abstract

We report a type of polar coordinate system adaptable metasurface by which a three-dimensional Bessel beam in broadband of 2–6 kHz is realized. For the common design of metasurface, many kinds elements are for a square lattice in the Cartesian coordinate system while sometimes a cylindrical symmetric source can be more suitable for practical working conditions, the 3D Bessel beam for example. Here, we present a unit cell for metasurface by embedding helical blades into an element of required shape. Thus, the lattice structure can be adjusted easily to the distinct coordinate systems. Hence, the arrangement of the elements can be more flexible, which means a larger freedom of design for the requirement of bi-anisotropic metasurfaces can be obtained. With the advantage of helical blades, an ideal control over energy transmission efficiency can be achieved too. Based on this, we investigated the characteristics and performance of the elements and realized a better performed Bessel beam in three dimensional. This design thinking can also be utilized to other kinds of wavefront modulation in broadband for both transmission and reflection control.