Abstract
In this paper, we propose a bilayer metasurface with dual-operating modes to realize the generation and conversion of dual-band Laguerre-Gaussian beam with different OAM. The bilayer metasurface consists of amorphous silicon (a-Si) and amorphous antimony selenide (a-Sb2Se3). In transmission mode, the metasurface can transform incident left-handed circularly polarized (LCP) Gaussian beam into one LCP Laguerre-Gaussian beam carrying topological charge l=−2 and one right-handed circularly polarized (RCP) Laguerre-Gaussian beam carrying topological charge l=−1, which enabled OAM modes multiplexing. In reflection mode, the metasurface can convert an incident LCP Gaussian beam into a LCP Laguerre-Gaussian beam carrying a topological charge l=−3 owing to the a-Sb2Se3 nanopillar that acts as a half-wave plate with high reflectivity. In addition, the OAM conversion between two arbitrary modes can be realized by the proposed metasurface. This work provides a valid method for OAM multiplexing and conversion, which holds a great applications value in high-speed optical communication systems.
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