Controlling Diffraction Patterns with Metagratings

In this study, we elaborate on the recent concept of metagratings proposed in Ra'di et al. [Phys. Rev. Lett. 119, 067404 (2017)] for efficient manipulation of reflected waves. Essentially, a metagrating is a set of 1D arrays of polarization line currents which are engineered to cancel scattering in undesirable diffraction orders. We consider a general case of metagratings composed of N polarization electric line currents per supercell. This generalization is a necessary step to totally control diffraction patterns. We show that a metagrating having N equal to the number of plane waves scattered in the far field can be used to control the diffraction pattern. To validate the developed theoretical approach, anomalous and multichannel reflections are demonstrated with 3D full-wave simulations in the microwave regime at 10 GHz. The results are interesting for the metamaterials community as they allow one to significantly decrease the number of used elements and simplify the design of wave front manipulation devices, which is very convenient for optical and infrared frequency ranges. Our findings may also provide a way to develop efficient tunable antennas in the microwave domain.