A broadband achromatic metalens for focusing and imaging in the visible was developed by Chen et al. (2018). This metalens uses nanofins to control phase, group delay, and group delay dispersion, enabling large bandwidth achromatic focusing and imaging across the visible spectrum (470–670 nm). The metalens consists of a single layer of nanostructures with thickness on the order of the wavelength, and does not involve spatial multiplexing or cascading. It achieves diffraction-limited focusing and imaging, and can also perform white light imaging. The design allows for independent control of phase and group delay, enabling dispersion-tailored metalenses. The metalens is capable of transforming a low-cost spherical lens into a diffraction-limited, achromatic lens across the entire visible spectrum. The study demonstrates the potential of metalenses for applications in imaging, lithography, microscopy, and other optical technologies. The metalens is fabricated using electron beam lithography and atomic layer deposition. The authors also discuss the potential for further optimization and application in other regions of the electromagnetic spectrum. The study highlights the advantages of metalenses over conventional refractive optics, including compactness, nanoscale size, and the ability to achieve achromatic focusing and imaging over a broad bandwidth. The metalens is capable of achieving high imaging quality over a few square millimeters, corresponding to a 30-degree field of view. The study also addresses the challenges of chromatic aberration and the need for dispersion engineering to achieve achromatic focusing. The authors conclude that the development of broadband achromatic metalenses represents a significant advance in the field of metalenses, with potential applications in a wide range of optical technologies.A broadband achromatic metalens for focusing and imaging in the visible was developed by Chen et al. (2018). This metalens uses nanofins to control phase, group delay, and group delay dispersion, enabling large bandwidth achromatic focusing and imaging across the visible spectrum (470–670 nm). The metalens consists of a single layer of nanostructures with thickness on the order of the wavelength, and does not involve spatial multiplexing or cascading. It achieves diffraction-limited focusing and imaging, and can also perform white light imaging. The design allows for independent control of phase and group delay, enabling dispersion-tailored metalenses. The metalens is capable of transforming a low-cost spherical lens into a diffraction-limited, achromatic lens across the entire visible spectrum. The study demonstrates the potential of metalenses for applications in imaging, lithography, microscopy, and other optical technologies. The metalens is fabricated using electron beam lithography and atomic layer deposition. The authors also discuss the potential for further optimization and application in other regions of the electromagnetic spectrum. The study highlights the advantages of metalenses over conventional refractive optics, including compactness, nanoscale size, and the ability to achieve achromatic focusing and imaging over a broad bandwidth. The metalens is capable of achieving high imaging quality over a few square millimeters, corresponding to a 30-degree field of view. The study also addresses the challenges of chromatic aberration and the need for dispersion engineering to achieve achromatic focusing. The authors conclude that the development of broadband achromatic metalenses represents a significant advance in the field of metalenses, with potential applications in a wide range of optical technologies.