Simultaneous Spectral and Spatial Modulation for Color Printing and Holography Using All-Dielectric Metasurfaces.

Metasurfaces possess the outstanding ability to tailor phase, amplitude, and even spectral responses of light with an unprecedented ultrahigh resolution and thus have attracted significant interest. Here, we propose and experimentally demonstrate a novel meta-device that integrates color printing and computer-generated holograms within a single-layer dielectric metasurface by modulating spectral and spatial responses at subwavelength scale, simultaneously. In our design, such metasurface appears as a microscopic color image under white light illumination, while encrypting two different holographic images that can be projected at the far-field when illuminated with red and green laser beams. We choose amorphous silicon dimers and nanofins as building components and use a modified parallel Gerchberg-Saxton algorithm to obtain multiple subholograms with arbitrary spatial shapes for image-indexed arrangements while avoiding the loss of phase information. Such a method can further extend the design freedom of metasurfaces. By exploiting spectral and spatial control at the level of individual pixels, multiple sets of independent information can be introduced into a single-layer device; the additional complexity and enlarged information capacity are promising for novel applications such as information security and anticounterfeiting.