To meet the growing requirement of system integration, it is of great importance and interest to develop ultrathin optical devices with unusual functionalities. As one of the most rapidly expanding frontiers of nanophotonics, optical metasurfaces, or planar metamaterials with subwavelength thickness, have the potential to revolutionize classical optics by displacing refractive optics in many large-scale applications and creating completely new functionalities. Benefiting from the unprecedented capability of metasurfaces in the arbitrary control of light’s amplitude, phase and polarization at subwavelength resolution, optical metasurfaces have provided us new opportunities to fully control the wavefront of light with planar elements and thus realize flat optics based optical devices. In this paper, I am going to highlight our work in dual-polarity metalens, multifunctional metalens, light sword lens, image-switchable holograms, arbitrary polarization manipulation for security, multichannel device for manipulation of twisted light beams and so on. The metasurface have provided unprecedented freedom in engineering the properties of optical waves with the highefficiency light utilization and a minimal footprint for security and defence. The unique properties of these novel metadevices can bring many of the completely new instruments to our daily lives.
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