Low cost 3D printable metamaterial for focused orbital angular momentum generation using mm-wave radar chip technology

We present a metamaterial for orbital angular momentum generation in the millimeter wave regime that can be fabricated with low-cost fused deposition modeling (FDM) 3D printers. The metamaterial induces a spatially distributed phase shift on millimeter waves, passing through the sample, via a spatial variation of the effective permittivity. We use an analytical model to calculate the effective permittivity of the metamaterial unit cell, which consists of a square block made of a dielectric with a cylindrical air hole at its center. The analytical model is used to design a metasurface that generates a beam carrying orbital angular momentum of order $l=1$. We prove this concept in a laboratory setup using a commercially available millimeter wave chip as the source.