Researchers have developed a novel way of generating color 3D images using a reflective metasurface performing through the entire visible spectral range. Metasurfaces are 2D engineered materials typically made of subwavelength elements, which provide excellent control over the shaping of optical wavefront via the manipulation of polarization, phase, and amplitude of the light.
Unlike typical metasurface-based holography techniques, the developed method does not rely on interleaved nanostructures for wavelength multiplexing or wavelength-dependent off-axis illumination. Instead, the researchers used specially-designed aluminum nanostructures to achieve high efficiency for metasurfaces across the visible spectrum, including the three main RGB colors.
A combination of specular and diffuse reflections was employed to generate images of 2D structures with 3D effects. The true perception of a 3D object through shading effects is therefore ensured by an adequate change in the brightness of the reflected light from the flat metasurface in response to variations in the illumination or observation angle. In contrast with 3D holograms, this structure performs under incoherent illumination.