Holography has numerous applications in beam shaping, product authentication, and in the entertainment industry. Recognizing that the large pixel size, limited viewing angle, lack of full-color performance, and limited phase modulation ability of traditional holograms limits their potential, Xiangang Luo from the State Key Laboratory of Optical Technologies on Nano-fabrication and Micro-engineering (SKLOTNM) at the Chinese Academy of Sciences (Chengdu, China) and professor Minghui Hong's team from the National University of Singapore have demonstrated full-color 3D meta-holography by using a nanostructured metallic surface.
By spatially adjusting the orientation angle of rectangular holes in a 75-nm-thick chromium film, the phase modulation can be controlled across the full color range. The pixel size of the hologram is 200 × 200 nm—smaller than the wavelength of visible light and much smaller than the approximately 8 × 8 μm pixel sizes of spatial-light-modulator-based holograms—and enables a viewing angle greater than ±90°. An off-axis illumination method shifts the holographic image for different colors, overcoming crosstalk issues. For example, a seven-color holographic image of the Chinese Sun Phoenix pattern has high image quality and a 5X better signal-to-noise ratio than other meta-hologram methods. 3D holographic imaging was also realized by recording the image information into the flat meta-hologram based on a modified point-source algorithm. The high density of plasmonic pixels on the metamaterial hologram paves the way for future 3D matrix-free displays. Reference: X. Li et al., Sci. Adv., 2, 11, e1601102 (Nov. 2, 2016).
