Metasurface for Bending the Reflected Wave Under Oblique Incidence

Metasurfaces enable a new degree of controlling electromagnetic (EM) wave by modulating subwavelength artificial structures. In this article, a reflection-type metasurface based on the modified Pancharatnam Berry (P-B) phase elements is proposed to manipulate the reflected EM wave under oblique incidence. Based on the modified P-B phase, the desired linear phase gradient along the x-axis can be achieved at the interface of the metasurface by adjusting the rotation angle of the unit cells. When a circularly polarized EM wave illuminates on the metasurface obliquely, the anomalous reflected wave can be observed in a broad bandwidth with high efficiency, and the reflection angle can be predicted by the generalized snell's law. Two metasurfaces with different phase gradients are designed in this article. The simulated results agree well with the theoretical designs, showing outstanding ability to manipulate the propagation of the EM wave. With specific phase gradient of the proposed metasurface, the anomalous reflected wave can be bent to the same side of the normal with the incident wave, which means that negative reflection effect can be achieved. Our design provides a solution to manipulate reflected beam under oblique incidence with high conversion efficiency, which has great practical applications in medical imaging, communication technology, and energy harvesting.