Ultra-dispersive metasurfaces enabled by convergence-phase design using simplified nanopillar arrays.

Metasurfaces offer unique advantages in manipulating the dispersion of optical fields; yet the achievable dispersion of metasurfaces has long been constrained by the limited phase modulation of complex nanostructures. Here we introduce a metasurface design method based on convergence phase that enables ultra-dispersive metasurfaces using structurally simple nanopillars with relaxed fabrication requirements. By overlapping phase of multiple wavelengths with that of a central wavelength, we demonstrated an ultra-dispersive metalens supporting phase variations exceeding 1200π - a more than 30-fold enhancement over existing approaches. Leveraging this method, we fabricated metalenses that exhibit unprecedented dispersion characteristics and implemented the metalens in a miniaturized chromatic confocal sensor for a measurement range of 13 mm with an axial resolution of 50 nm. Additionally, we demonstrated millimeter-scale depth-of-field spectral tomography, highlighting the significant advantage and immense potential of our method. Our research has established a generalizable theoretical foundation for designing ultra-dispersive metasurfaces that can be mass-produced and deployed for practical applications.