High-NA, Confocal, Achromatic Bifocal Metalens for Dual-Wavelength Parallel Focusing

To address this, we propose and numerically demonstrate a novel dual-wavelength achromatic bifocal metalens. Our design leverages a hybrid strategy, combining a spatial interleaving scheme with the complete decoupling of propagation and geometric phases.

This creates a platform capable of independently processing multiple wavelength and polarization channels. Simulation results confirm that the metalens focuses 450 and 532 nm light to two near-diffraction-limited spots on a single plane, maintaining a high effective NA of 0.81 and near-perfect energy symmetry (<0.01% imbalance). This work validates a scalable design philosophy and paves a new way toward ultra-compact optical read/write heads for multidimensional, parallel, and high-density optical storage.