Wide-angle And High-efficiency Metagrating Holography In The Full Visible

Optical metasurface,a 2D array of plasmonic or dielectric optical meta-atoms,provides a versatile and compact platform for manipulating the polarization,phase and amplitude of light.It has been used to design planar optical functional elements such as ultrathin metasurface lens,metasurface waveplates,polarization beam splitter and so on.More generally,metasurface is capable of shaping the general and complex wavefront of light through holography techniques.Beyond gradient metasurfaces,metagratings capable of diffraction order management provide a facile and efficient way for extreme wavefront steering.Previous transmissive metagratings heavily resort to compound asymmetric inclusions to achieve single-channel near-perfect diffraction.However,such complex inclusions are sensitive to geometric parameters and lack the flexibility for arbitrary phase modulation,restricting applications only for beam deflection.Here,we show that perfect diffraction in all-dielectric transmissive metagratings with simple rectangular inclusions can be achieved through proper multipole interference and lattice coupling.Implementing such metagrating by CMOS-compatible Silicon Nitride(Si N_x)nanobars,we experimentally demonstrate analog phase profile encoding of a hologram through displacement modulation of continuous Si N_x nanobars(generalized detour phase),manifesting broadband and wide-angle high diffraction efficiencies for both polarizations at the full visible range.In addition,we demonstrated a full-color hologram strategy based on the metagrating configuration.Featured with such extreme angle/wavelength/polarization tolerance and enormously alleviated structural complexity for both design and fabrication,our demonstration unlocks the full potential of metagrating based wavefront shaping devices for improved practicability and industrial mass-production.