Robust Metasurfaces Using Versatile Encapsulation Coating Without Critical Optical Losses

Metasurfaces, which are comprised of 2D subwavelength artificial structures, have been extensively studied owing to their unprecedented wavefront manipulations, especially for visible range. By virtue of these capabilities, metasurfaces can serve as highly functionalized photonic systems, such as metalenses, and metaholograms, with the great pliability of electromagnetic wave control. Despite these benefits, many professionals predict that metasurfaces are challenging to be utilized realistic devices, because of their low robustness. Nowadays, dielectric metasurfaces have been devised to avoid a decrease in efficiency. These optical losses are induced by the electron oscillation of metal when light comes. Particularly, hydrogenated amorphous silicon (a-Si:H) which has a high refractive index and low extinction coefficient has been developed to implement high-efficiency dielectric metasurfaces at the visible. Here, we propose high-efficient and high-robustness encapsulated metasurfaces through bandgap engineering of hydrogenated amorphous silicon, achieving 95% in 532 nm wavelength. We vary the atomic arrangement of hydrogenated amorphous silicon by optimizing process terms of plasma-enhanced chemical vapor deposition for high-efficient dielectric metasurfaces. Moreover, encapsulation coating using atomic layer deposition and spin-on glass enables self-cleaning and high abrasion-resistant metasurfaces, while maintaining high efficiency in the visible frequencies. Unlike conventional metasurfaces, the introduced encapsulated metasurfaces can strongly resist external contaminations and abrasions. We believe that our novel method, enhancing the robustness of metasurfaces, can be applied to pragmatic outdoor applications.