As part of an international collaboration with Southern University of Science and Technology in Shenzhen (China), London Centre for Nanotechnology researchers at King’s College London have developed a novel way of generating color 3-D images using a reflective metasurface performing through the entire visible spectral range. Metasurfaces are 2-D engineered materials typically made of subwavelength elements, which provide excellent control over the shaping of optical wavefronts via the manipulation of polarisation, 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 identical aluminium nanostructures to achieve a high metasurface efficiency across the visible spectrum, including the three main RGB colors. A combination of specular and diffuse reflections was employed to generate images of 2-D structures with 3-D effects. The true perception of a 3-D 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 3-D holograms, this structure performs under incoherent illumination.
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Source: Phys.org