PORTLAND, Ore.--The e-readers of the future could use plasmonic resonator arrays as wide field-of-view color filters for reflected light, according to University of Michigan researchers, who demonstrated how nano-slits could induce the effect, creating reflective displays with vivid colors that can be viewed at nearly any angle--even in bright sunlight.
Micro-electro-mechanical systems (MEMS) have already demonstrated how to fashion reflective displays that filter light by reinforcing colors of a wavelength proportional to a slit's depth, but the University of Michigan technology varied both the depth and the width of slits in order to induce a localized resonance that funnels specific colors of light into the grooves consistently over a 160-degree field-of-view.
"There is a wide degree of latitude available when modifying the filtered color by changing either the depth or the width," said professor Jay Guo, who performed the work with doctoral candidates Yi-Kuei Ryan Wu and Cheng Zhang at the University of Michigan along with Sandia National Laboratories scientist Andrew Hollowell. "And by only changing the nano-groove's width, while maintaining a constant depth, the fabrication process can be greatly simplified and easily scaled up to large-area devices."
University of Michigan researchers have taken a step toward an elsuve goal--imitating nature by creating a system that reflects light of certain wavelengths to result in brilliant color, such as a peacock's iridescent tail.
Image credit: sxc.hu user doc_
According to the researchers, the width of the slits induces a polarization charge-pair that acts as a dipole to alter the electrical field of the incident light, redirecting specific wavelengths into the groove. For implementing the technology in reflective displays, that polarization dependence could enable multifunctional components to be created, ones that serve as an electrode, polarizer and color filter simultaneously.
Currently, the researchers are only demonstrating still images. But they plan to next develop a moving display using the technology. The project is funded by the U.S. Air Force Office of Scientific Research and the National Science Foundation. The paper, Angle-Insensitive Structural Colors based on Metallic Nanocavities, is available free online.
Specific colors of light are reflected from grooves whose width is inversely proportional to their wavelength, here purple, blue, green, brown and yellow.