Binary Huygens metalens based on congener dipoles

Huygens metasurfaces enable efficient wavefront control through interference of electric and magnetic dipoles. Here, we design a binary Huygens metalens operating at 850 nm using silicon double-disk meta-atoms that support a pair of congeneric electric dipole resonances. By jointly tuning the disk radius and spacer thickness, we obtain two unit cells that provide phase shifts close to 0 and π while maintaining similarly high transmission, enabling a binary phase profile with minimal efficiency penalty. A 41 × 41-element metalens based on these two states produces a tight focal spot at a distance of 2.31 µm from the metasurface with transmission above 90% for both phase configurations. These results show that phase binarization can substantially simplify Huygens metalens implementation without sacrificing focusing performance at telecom-relevant wavelengths.