The article is open access (CC-BY 4.0) and is available here: https://doi.org/10.1038/s41377-018-0078-x https://doi.org/10.1038/s41377-018-0078-x Fresnel zone

The article is open access (CC-BY 4.0) and is available here: https://doi.org/10.1038/s41377-018-0078-x https://doi.org/10.1038/s41377-018-0078-x Fresnel zone plates are not new, but they only work at a single wavelength. https://en.wikipedia.org/wiki/Zone_plate https://en.wikipedia.org/wiki/Zone_plate This means that they are not achromatic. https://en.wikipedia.org/wiki/Achromatic_lens https://en.wikipedia.org/wiki/Achromatic_lens The Shrestha et al. article uses nano-structured silicon to focus wavelengths between 1200 nm (near-infrared) and 1600 nm (short-wavelength infrared); for comparison, the tail end of visible light is around 740 nm. It's impressive to get such a large range of wavelength (bandwidth), hence the "broadband" and "achromatic" in the title.