  Gradient metasurfaces have been extensively applied in recent years for
enabling an unprecedented control of light beam over thin optical components.
However, these metasurfaces suffer from low efficiency when it comes to bending
light with large angle and high fabrication demand when it requires fine
discretion. In this work, we investigate the all-dielectric metagrating based
on mie-type resonances interference, allowing extraordinary optical diffraction
for beam steering with ultralarge angle. It is found that the coupling inside
and among lattice of metagrating can tune the exciting state of electric and
magnetic resonances including both fundamental dipoles and high-order
multipoles, leading to ideal asymmetrical scattering pattern for redistributing
the energy between the diffraction channels at will. The participation of
quadrupole and hexapole not only significantly enhance the working efficiency,
but also bring distinctive possibilities for wave manipulation which cannot be
reached by dipoles. Utilizing a thin array of silicon rods, large-angle
negative refraction and reflection are demonstrated with almost unity
efficiency under both polarizations. Compared with conventional metasurfaces,
such an all-dielectric mategrating has the merits of high flexibility, high
efficiency and low fabrication demand. The strong coupling and prosperous
interactions among multipoles may behave as a cornerstone for broad range of
wavefront control and offer an effective solution for various on-chip optical
wave control such as bending, focusing, filtering and sensing.
