Dispersion controlling meta-lens at visible frequency.

Dispersion management is crucial in constructing spectrometers, superprisms, and achromatic lens systems. Unfortunately, the dispersion of natural materials is determined by the molecular energy levels with limited tunability, and thus conventional methods of dispersion controlling are complex and need to trade off other aberration. Metasurface offers an alternative method to overcome those limits via utilizing dedicatedly designed nanostructures that response to special wavelength, which results in well-engineered dispersions. As proof of the concept, we design a series of flat dielectric metasurface lenses, which are able to steer the dispersion arbitrarily for three wavelengths at visible frequency (473, 532, and 632.8 nm). Based on the unique dispersion engineering ability of metasurface, the achromatic meta-lens and the super-dispersion meta-lenses are realized. Furthermore, the light of different wavelengths can be focused on any desired spatial positions.