Twofold Polarization-Selective All-Dielectric Trifoci Metalens for Linearly Polarized Visible Light

A metasurface that features an exotic ability to arbitrarily manipulate properties of light waves at the subwavelength scale has received a burgeoning amount of interest in the field of photonic multitasking. Unlike the previous multifunctional metasurfaces, which rely on the spatial multiplexing of plasmonic nanorods/nanoapertures with identical dimensions and spatially varying orientations, multiple distinct rectangular-shaped hydrogenated amorphous silicon nanoposts are tapped into to create a twofold all-polarization-controlled trifunctional metasurface. By judiciously interleaving the dielectric nanoposts, of which the lateral widths and angles of orientation can be adjusted to allow for a full 2π-phase control, the metasurface shows a salient feature to empower triple functionalities by simultaneously tailoring the linear polarization of incident and transmitted light. As a proof of concept, a visible-frequency trifoci metalens is designed, fabricated, and characterized, from which the three foci at distinct focal planes along the longitudinal direction are successfully attained. Substantially reduced functional crosstalk among different foci is also experimentally validated. The proposed approach is straightforward and thus can lead to the development of a wide array of multifunctional metadevices for diverse optical wave manipulations, such as the multiplexing of optical vortices and various applications in anticounterfeiting, high-density information encryption, holography, and display.