Orthogonal manipulations of phase and phase dispersion in realization of azimuthal angle-resolved focusings

Abstract

In conventional achromatic metasurfaces configurations where the engineering paths of phase and phase dispersion are the same, limited phase dispersion control range inevitably imposes a restriction on the broadband device size, which otherwise can be arranged in a periodic manner to achieve infinite size at a single wavelength. In addition to this, the adoption of geometric-phase structures imparts the orthogonal circular polarization conversion, whereas the birefringent propagation-phase structures bring an uncertain polarization state, thus resulting in an incomplete polarization conversion. In this study, we propose an azimuthal angle-resolved beam-deflection metasurface at the same polar angle with orthogonal phase and phase dispersion control paths. Periodic expansion is implemented to achieve unlimited device size along the phase control path and the broadband light is monotonously and azimuthally deflected to the designated polar angle with the delicate design along the dispersion path. In addition, the non-crossed polarized light arising from the incomplete geometric phase control would naturally separate from the cross-polarized light when adjusting the planar geometric parameters of the birefringent metaatoms to realize dispersion control. This design scenario may find applications in phased-array detection applications where beams are azimuthally swept to search targets at one polar angle.