Dielectric metasurfaces working at visible frequencies have been steadily investigated to realize practical flat optical components. However, recently investigated dielectrics, TiO2 and GaN suffer high fabrication costs since a precursor of TiO2 is expensive, and GaN requires two-step etching process. Here, this work suggests optical-loss-suppressed hydrogenated amorphous silicon (a-Si:H) for functional metasurfaces. Optical losses in the visible frequencies are manipulated by adjusting deposition conditions of plasma-enhanced chemical vapor deposition. Optical properties of a-Si:H are optimized for geometric metasurfaces, and it exhibits a high refractive index over 3.0 with low extinction coefficient (<0.1). Using them, highly efficient beam-steering metasurfaces, encapsulated metalenses, and bright structural coloration has been demonstrated. Considering that our manipulation efficiency approaches 42%, 65%, and 75% at the wavelength of 450, 532, 635 nm, it will be dominant materials for a functional photonic platform with low-fabrication costs.
|