Millimeter‐Scale Single‐Layer RGB Achromatic Metalens via Time‐Simultaneity‐Free Design

Compact and high‐performance optical components are essential for miniaturizing next‐generation imaging and display systems. While metalenses offer a promising ultrathin alternative to refractive optics, scaling up achromatic metalenses is fundamentally hindered by the trade‐off between aperture size and operational bandwidth. In this study, we propose a time‐simultaneity‐free (TSF) approach that strategically abandons temporal simultaneity. By introducing wavelength‐dependent DC phase biases into the target phase profiles, we reframe the design as a global phase‐space alignment problem, enabling simultaneous phase matching across the red, green, and blue (RGB) wavelengths. Crucially, our theoretical scaling analysis reveals that the multi‐wavelength phase efficiency asymptotically converges to a stable lower bound in the large‐aperture regime, indicating the potential for macroscopic scalability. Based on this mechanism, we experimentally demonstrate a single‐layer, polarization‐insensitive silicon nitride metalens with a diameter of 1 mm and a numerical aperture of 0.1. The fabricated device achieves near‐diffraction‐limited focusing with Strehl ratios of 0.80, 0.97, and 0.95 at 450, 532, and 633 nm, respectively, while tightly bounding focal‐length deviations within % to %. Furthermore, high‐fidelity, full‐color imaging of test targets and graphics is successfully demonstrated using a commercial CMOS image sensor. These results provide a highly scalable, application‐driven paradigm for macroscopic multi‐wavelength metasurface optics.