Circular polarizer via selective excitation of photonic angular momentum states in metamaterials

We propose a scheme in realizing a compact circular polarizer by using a metamaterial with a properly designed input meta-surface. This scheme is based on the selective excitation of photonic angular momentum states in a coaxial element array by the symmetry-broken input meta-surface. The topological charge m of the excited photonic angular momentum state in the coaxial element determines the handedness of the transmitted light via the orbit-spin conversion of the angular momentum of light. A net circular-polarization generation efficiency of 64.5% for a linearly polarized incidence is demonstrated.