Flat Optics with Metasurfaces | Metalens

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Work from Havard, 2016, presented by Reza Khorasaninejad. In 2017 it was improved: "Last summer, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) announced a new, flat lens that could focus light with high efficiency within the visible spectrum. The lens used an ultrathin array of nanopillars to bend and focus light as it passed.
The announcement was hailed as a breakthrough in optics and was named among Science Magazine's top discoveries of 2016.
But the lens had a limitation – it could only focus one color at a time. Now, the same team has developed the first flat lens that works within a continual bandwidth of colors, from blue to green. This bandwidth, close to that of an LED, paves the way for new applications in imaging, spectroscopy and sensing. The research is published in Nano Letters."