Spin-decoupled metasurfaces for the generation of self-accelerating vector beams

The ability to generate structured light with arbitrary controlled polarization in a compact optical path has been challenging for the last few years in the optics and photonics fields. In this regard, for the first time in our knowledge, this work proposes the design, fabrication, and characterization of spin-decoupled metasurfaces able to generate self-accelerating orbital angular momentum beams having variant topological charges. Illuminated such metasurfaces with a linearly polarized light we are able to generate vector beams and, depending on the polarization angle it is possible to explore different states of the Hybrid Poincaré Sphere (HPS). Our metaoptics are designed as an array of periodic subwavelength metastructures (the so-called meta-atoms) composed of silicon nanofins on a silicon substrate. Each meta-atom acts like a half-wave plate that exploits both the geometrical and dynamical phases in a different way depending on its position on the entire optical element. This design solution offers both compactness of the optical path and easy integration with other optical elements. In particular, the proposed metaoptics are suitable for telecommunications, imaging, particle manipulation, and quantum applications.