Most traditional multicolor vision technologies is based on the superimposition of three primary colors, i.e., red, green, and blue (RGB). However, lots of light sensors and retinas of animals are sensitive to a wide range of wavelengths, which requires a much larger color gamut than the one mixed by RGB.
In an article published in Science Advances, a journal established by the American Association for the Advancement of Science, Prof. Xiangang Luo’s team from the State Key Laboratory of Optical Technologies on Nano-fabrication and Micro-engineering (SKLOTNM), Institute of Optics and Electronics, Chinese Academy of Sciences, and Prof. Minghui Hong’s team from Department of Electrical and Computer Engineering, National University of Singapore have demonstrated that multicolor imaging with seven primary colors can be realized by a single layer of nanostructured metallic surface. The results have been published in Science Advances.
The metasurface is constructed by nano-rectangular holes in a 75-nm-thick chromium film. The phase modulation within the entire visible color range is fully controlled by spatially adjusting the orientation angle of the nano-rectangular holes, due to the intrinsic achromatic feature of the structure. In order to overcome the cross-talk among different colors, that normally exists in current metasurface holography, they introduced an off-axis illumination method to shift the holographic image in different colors and successfully reconstructed all visible colors in the imaging area. This method not only leads to a remarkable image quality, with a signal-to-noise ratio (SNR) five times better than those of the previous meta-hologram designs, but also paves the way to create new meta-hologram devices.
To illustrate their reconstructed holographic images, they made a colorful Sun Phoenix with seven primary colors, including red, orange, yellow, green, cyan, blue, and purple. Multicolor 3D imaging were also demonstrated. This work has a potential in broad applications, e.g., data storage, security, and authentication. For the topic of authentication, it is possible to fabricate a super-thin meta-hologram including both the visible and “invisible” image patterns at a specific wavelength, so the holographic image contains “secret” information invisible to the human eyes. Furthermore, for the data security applications, introducing more wavelengths is similar to increasing the length of the password, which increases the order of the complexity and enhances the security level.
Paper information: Xiong Li, Lianwei Chen, Yang Li, Xiaohu Zhang, Mingbo Pu, Zeyu Zhao, Xiaoliang Ma, Yanqin Wang, Minghui Hong & Xiangang Luo “Multicolor 3D meta-holography by broadband plasmonic modulation”. Sci. Adv. 2, e1601102 (2016). 10.1126/sciadv.1601102