Manipulation of Orbital Angular Momentum Spectrum Using Shape-Tailored Metasurfaces

Vortex beams carrying orbital angular momentum (OAM) are widely applied in various electromagnetic, optical, and quantum systems. A tailored OAM spectrum composed of several specific modes as expected holds a promise for expanding the degrees of freedom of the systems. However, such a broadband high-purity tailored spectrum is difficult to be achieved by the present devices, where the broadband amplitude manipulation is not explored yet. In this work, inspired by the envelope-modulation theory, an elegant and universal way to manipulate the OAM spectrum in wide bandwidth is proposed by using a shape-tailored metasurface. First, the rotating meta-atoms on a triangular lattice are proved to have smaller coupling distortion than that on a square lattice, and this behavior is critical for high-purity vortex spectrum generation by the Pancharatnam-Berry-based metasurfaces. Second, a universal modulation relation is established between the spatial arrangement of metasurfaces and the generated vortex beams. Finally, the broadband-modulated OAM spectra and the comb-like OAM spectra are theoretically and experimentally demonstrated by the shape-tailored metasurfaces. The proposed amplitude-modulation scheme offers a novel concept and engineering route to manipulate the OAM spectrum in wide bandwidth, which can promote the development of OAM-based applications.

Automated summary

Inspired by the envelope-modulation theory, a novel and universal method for manipulating the OAM spectrum in wide bandwidth is proposed using shape-tailored metasurfaces. This approach successfully demonstrates the generation of broadband-modulated OAM spectra and comb-like OAM spectra, showing potential for advancing OAM-based applications.