Broadband quarter-wave birefringent meta-mirrors for generating sub-diffraction vector fields

Independent manipulation of phase and polarization of optical fields is of great interest in various applications, including vector-field generation, optical tweezers, and nanolithography. The integration of phase and polarization manipulation on a single optical device may greatly simplify optical systems and eases optical alignment. In this Letter, a family of reflective cross-shaped quarter-wave birefringent metasurfaces is proposed to achieve full control of polarization and phase of reflected waves. Based on the proposed metasurfaces, two meta-mirrors are designed with integrated functions of polarization conversion and sub-diffraction focusing. Numerical investigations also reveal the achromatic focusing performance of the two meta-mirrors. The proposed metasurfaces with independent manipulation of polarization and phase provide flexible building blocks for constructing complicated vector optical fields.