Abstract
Pancharatnam-Berry geometric phase has attracted enormous interest in subwavelength optics and electromagnetics during the past several decades. Traditional theory predicts that the geometric phase is equal to twice the rotation angle of anisotropic elements. Here, we show that high-order geometric phases equal to multiple times the rotation angle could be achieved by meta-atoms with highfold rotational symmetries. As a proof of concept, the broadband angular spin Hall effect of light and optical vortices is experimentally demonstrated by using plasmonic metasurfaces consisting of space-variant nanoapertures with C2, C3, and C5 rotational symmetries. The results provide a fundamentally new understanding of the geometric phase as well as light-matter interaction in nanophotonics.
Highlights
We show that high-order geometric phases equal to multiple times the rotation angle could be achieved by meta-atoms with highfold rotational symmetries
As a novel phase shift mechanism, the PancharatnamBerry geometric phase is a direct result of spin-orbit coupling of photons in structured materials, which has been widely used to control the light wave front and to design various types of functional metadevices known as geometric phase metasurfaces [1,2]
In this Letter, we show for the first time that subwavelength structures with rotational symmetry ≥ 3 can tailor the optical anisotropy owing to the lattice coupling effect, and further, high-order geometric phases that manifest as multiple times the rotation angle of the elements could be achieved in the linear optics regime
Summary
As a novel phase shift mechanism, the PancharatnamBerry geometric phase is a direct result of spin-orbit coupling of photons in structured materials, which has been widely used to control the light wave front and to design various types of functional metadevices known as geometric phase metasurfaces [1,2]. We show that high-order geometric phases equal to multiple times the rotation angle could be achieved by meta-atoms with highfold rotational symmetries. In this Letter, we show for the first time that subwavelength structures with rotational symmetry ≥ 3 can tailor the optical anisotropy owing to the lattice coupling effect, and further, high-order geometric phases that manifest as multiple times the rotation angle of the elements could be achieved in the linear optics regime.
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