Highly efficient anomalous reflection by ultrathin phase gradient planar meta-surface arrays in near infrared region

The higher efficient anomalous reflection performance in short wavelength region is carefully designed and numerically demonstrated based on an ultrathin phase gradient meta-surface arrays. These meta-surfaces, comprising a periodic arrangement of metal nanobricks configurations providing required phase shift for the reflected beam from 0 degrees to 360, exhibit a higher conversion efficiency of about 87% limited by Ohmic loss in the metal to anomalous reflection mode at normal incidence. Importantly, the light polarization of the anomalous reflection is same as that of the incident wave. The generalized Snell's law is verified by the near field propagating characteristics of a plane wave and the far field distribution. Compared with a conventional optical phase shifts components, new degrees of designed freedom can be attained by introducing this abrupt linear phase variation along the ultrathin planar interface. Based on these metasurfaces with the great flexibility in manipulation of light beam, some optical components with inaccessible functionalities by a traditional nanostructure can be realized. Further, the discrete elements in a unit array are replaced by the continuous one, in which the anomalous reflection phenomenon also arises.