From the summary article, it looks like they have made a Fresnel lens, which can also be quite flat but works over a limited wavelength range of light. In orde

From the summary article, it looks like they have made a Fresnel lens, which can also be quite flat but works over a limited wavelength range of light. In order to achieve broadband operation, the phase change vs wavelength of the metamaterial needs to approximate a large delay. If a large delay is not feasible to implement, this summary is overstating the importance of this result compared to prior technology.