Multifunctional all-dielectric nanosurfaces for generation and detection of focused optical vortices

Metasurfaces, the planner counterpart of three-dimensional metamaterials, promise a superior degree of freedom and design flexibility due to their unprecedented capability to manipulate the wavefront of incident light. These nanostructures can precisely tailor the intrinsic properties of the light to implement multifunctional and miniaturized nanophotonic devices. Due to the ever-increasing demand for compactness, it is essential to independently control the amplitude, phase, and polarization of light and integrate multiple functionalities in a single-layered device. This paper introduces multifunctional all-dielectric metasurfaces that integrate numerous optical phenomena in a single meta-device for the ultraviolet spectrum. A nanoantenna made of bandgap-engineered material silicon nitride (Si3N4) is used as a fundamental building block of proposed metasurfaces. The proposed design methodology is verified by realizing multiple metasurfaces to generate focused optical vortices of different topological charges. The multifunctional capability of the proposed metasurfaces is achieved by exploiting the spin-decoupling technique that provides a unique optical response under different handedness of the incidence light. To further validate the functionality of the proposed metasurfaces, a unique design technique is also presented that resolves the value of the topological charge embedded in any optical vortex beam by reading the number of spirals and their spinning directions. The proposed approach can lead to a new paradigm in realizing multifunctional nanophotonic devices for optical wave manipulations, such as high-density information encryption, optical anti-counterfeiting, optical storage, and multiplexing of optical vortices.