Polarization-dependent bifocal metalens enabled by dielectrically chiral metasurfaces

Abstract This work presents a novel dielectrically chiral bifocal metalens based on the mechanisms of the Pancharatnam-Berry (PB) phase and propagation phase. Dielectric chirality is incorporated into the all-dielectric nanopillars of the metasurface, forming the metalens. Unlike other works primarily dedicated to achieving symmetric polarization-dependent responses, our approach not only realizes distinct circular polarization-selective focusing behavior for different incident polarization states of light but also exhibits polarization-dependent focal shifts and asymmetric energy redistributions between the focal spots. By increasing the strength of chirality, the full width at half maximum for both focal spots becomes identical while the separation distance between them shortens. At the same time, one of the focal spots becomes dominant. This chirality-based control mechanism provides new possibilities for applications in polarization-based beam steering, and particle manipulation.