Polarization-dependent bifocal metalens enabled by dielectrically chiral metasurfaces

Abstract This work presents a dielectrically chiral bifocal metalens based on the mechanisms of the Pancharatnam–Berry phase and propagation phase. By incorporating dielectric chirality into the all-dielectric nanopillars of the metasurface, the design enables distinct circular polarization-selective focusing behaviour for different incident polarization states of light. Unlike other works primarily dedicated to achieving symmetric polarization-dependent responses, our approach not only realizes distinct circular polarization-selective focusing behaviour 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 expands the potential applications of metasurfaces in polarization-based beam steering and particle manipulation.