| Summary: | Metasurfaces, ultrathin two-dimensional arrays of artificially engineered meta-atoms, can impart spatially varying changes towards the incident electromagnetic wave and provide versatile functionalities once unprecedented in sub-wavelength thick natural materials. The wavefront manipulation by metasurfaces usually arises from the strong resonant behaviors of varied meta-atoms in subwavelength lattice, which also brings some drawbacks like the unexpected dispersion due to separate resonances of the meta-atoms and the long concerned low efficiency problem. This paper reviews the recent surge of fruitful works on dispersion and efficiency engineering of metasurfaces and provides an overview of several effective methods to acquire metasurfaces with these distinctive features.
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