Aperiodic metalenses: intrinsically near-achromatic visible focusing with identical nanocylinders

Conventional metalenses control light by varying meta-atom geometry, a design strategy that inherently couples phase modulation to structural dimensions and exacerbates chromatic dispersion. Here, we break this paradigm by decoupling phase control from meta-atom geometry. We introduce an aperiodic metalens architecture composed exclusively of structurally identical dielectric nanorods, where full 2{\pi} phase coverage is achieved solely through local periodicity modulation. We theoretically demonstrate that this geometric invariance yields a linear effective-refractive-index scaling that intrinsically satisfies the dispersive condition required for near-achromatic focusing. Operating in the visible spectrum, our aperiodic designs (moderate and high numerical apertures of 0.4 and 0.8) reveal a passive suppression of chromatic aberration. Compared to conventional size-variant designs, our aperiodic approach reduces longitudinal chromatic focal shift by nearly 42% and maintains superior spectral efficiency, yielding tighter, diffraction-limited focal spots. By relying on a single, fabrication-tolerant nanostructural building block, this approach offers a highly simplified and scalable route toward next-generation broadband metasurfaces.