Harvard researchers developed a new kind of tunable color filter that uses optical nanoantennae to control color output. A single active filter under exposure to different types of light can produce a range of colors.

Kenneth Crozier, associate professor of electrical engineering at the Harvard School of Engineering and Applied Sciences (SEAS), and colleagues engineered the size and shape of metal nanoparticles so that the color they appear depends on the polarization of the light illuminating them. Harvard has named the nano structures chromatic plasmonic polarizers.

By controlling the optical nanoantennas shape, the engineers created a controllable color filter, tuned to react differently with light of different colors and different polarizations, said co-author Tal Ellenbogen, a postdoctoral fellow at SEAS. Conventional RGB filters have one fixed output color and create a broader palette of hues through blending. Each pixel of the nanoantenna-based filters is dynamic and able to produce different colors when the polarization is changed. This can create a pixel with a uniform color or complex patterns with colors varying as a function of position.

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