Two-dimensional assemblies of subwavelength nano-antennas, also called metasurfaces, enable an advanced manipulation of visible light on ultra-compact material platforms, as required for next-generation optical devices. In this context, a particularly relevant feature of metasurfaces is their capability to convert a standard incident beam into scattered beams with the desired topological features. For instance, they allow generating vectorial vortex beams, which are appealing for high-throughput optical communications, as well as for polarimetry and sensing with spatial readout of polarization information. To achieve fully functional devices featuring multispectral capabilities, metasurfaces generating beams with the desired topology in a wavelength-dependent way are needed. Here, Michael Yannai and coworkers propose a metasurface design that generates beams with different topologies at two different wavelengths. It consists of an interleaved array of two kinds of dielectric nano-antennas resonating at two different wavelengths. It yields two non-spatially-overlapping 3×3 arrays of scattered beams, which present a linear polarization at one wavelength and consist of vectorial vortices with a radial or azimuthal polarization profile at the other wavelength.
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