Pancharatnam-Berry (PB) phase modulation leverages the precise linear correspondence between output phase and nanopillar rotation angle, enabling wide application in modulating focal spherical waves. However, the intrinsic material absorption of waveguide structure inevitably brings energy loss within the visible light spectral range, severely limiting focusing efficiency over broad bandwidths under general models of nanopillars. Here, we introduce a dual-coupled metalens composed of an air slot-etched rectangular TiO