Researchers at Missouri University of Science and Technology are using just one layer of nanoscale metallic film to reconstruct full color 3D holographic images. The team uses a new approach that has huge potential for applications such as printing 3D security marking onto credit cards and providing cell phones with 3D floating displays.
Some nanomaterials are only a few atoms in size as a nanometer is only one billionth of a meter.
The new method used involves ultrathin nanometer scale metallic films with metasurfaces that can be used to manipulate light’s wave front. The metasurface hologram developed by the team consists of an aluminum film 35 nanometer thick, perforated with tiny rectangular holes 80 nanometers high by 160 nanometers wide. A microfabrication process known as focused ion beam milling was used to create different orientation angles.
The team demonstrated full color holographic images that are clean and vivid, have high resolution and low noise. This was achieved by varying the interaction of red, green and blue laser light on metasurface structures. The three primary colors, red, green and blue, as well as the secondary colors cyan, magenta, yellow and white were produced. The researchers’ demonstration of their reconstructed holographic images consisted of the letters C, M, Y and W, a Rubik’ cube and an apple.
The metasurface hologram could hold promise for future applications such as big data storage, biomedical imaging, credit card security marking and 3D floating displays.
Yang, an assistant professor in mechanical and aerospace engineering at Missouri S&T explains that the phase delay is fully tuned through the slit by adjusting the orientation angle of the nanoscale slits. This achieves the phase modulation across the entire visible color range. Amplitude modulation is attained by simply including or not including the slit. High resolution, low noise holographic images can be reconstructed as the holograms contain both phase and amplitude modulations at nanometer scale.
The hologram looks like a needlepoint pattern when viewed with a scanning electron microscope with tiny rectangular slits with various orientation angles drilled through the aluminum metasurface layer.
Gao, co-author of the paper notes that while existing metasurface holograms are mostly designed for limited colors, the new model can successfully reconstruct almost all visible colors. This is because of the wavelength-multiplexed method, which introduces tilted incident angle illumination of laser light and encodes additional phase shifts into the holograms.
The method was described in the journal ACS Nano : “Full-Color Plasmonic Metasurface Holograms”.