Beam Manipulation Mechanisms of Dielectric Metasurfaces.

Dielectric metasurfaces can achieve flexible beam manipulations. Herein, we study dielectric metasurfaces with different refractive indices, periods, incident angles, and cross-sectional shapes to determine the metasurface working mechanisms. Perfect transmission mainly depends on multipolar interference that can be used to control the transmission modes through the hybrid periods, hybrid cross sections, and multilayers. Perfect reflection is strongly influenced by the period of the metasurface and occurs only when the period is shorter than incident wavelength, which can be attributed to the lattice coupling. Furthermore, lattice coupling can be classified into two types with distinct properties: vertical mode and horizontal mode coupling. The vertical mode appears when the effective wavelength matches the feature size, whereas the horizontal mode only appears when the incident wavelength is close to the period. The horizontal mode is sensitive to the incident angle. The revealed functioning mechanisms enable further practical applications of metasurfaces.