Metalens with tilted structures for high-efficiency focusing at large-angle incidences

The metalens has attracted remarkable attention due to its ultra-thin and ultra-light characteristics, which indicate great potential for compact imaging. However, the limited efficiency at a large angle incidence severely hinders the application of wide-angle focusing and imaging, which is pursued in the fast-developing imaging systems. Therefore, new strategies to improve the lens performance at large incident angles are in demand. In this work, we propose tilted structures for large- angle focusing with improved efficiency. Metalenses based on dynamic phase and geometric phase are designed and systematically characterized by numerical simulations. We show that tilted structures of unit cells significantly improve the lens performance at oblique incidences. In detail, the focusing efficiency of the metalens with tilted structures is increased over 25% at 30 degrees incidence, as well as the modulation transfer function. In addition, we develop a hybrid metalens array achieving highly efficient wide-angle imaging up to 120 degrees. We believe this design provides a feasible route toward wide-field and high-performance imaging applications.