Optimal design of beam-deflectors using extended unit-cell metagratings

Recent reports on metasurfaces have focused on beam-deflector, a canonical optical element that can be used to compose other functionalities. Most reported designs, however, are limited to small deflection angles; large-angle (≥ 50 degrees deflection) transmission-mode beam steering designs show poor efficiency. Furthermore, rapid efficiency degradation is observed for small deviations in the incidence angle. This paper presents a numerical study of beam-deflectors based on extended unit-cell metagratings (unit-cells containing multiple nanoantennae). In comparison to previous reports, the designs achieve significant efficiency improvements, wider acceptance angles and better polarization filtering. The versatility of the design technique is demonstrated by designing polarizing beam deflectors, polarization insensitive beam deflectors and prismatic beam deflectors.