Silicon Rich Nitride Huygens Metasurfaces in the Visible Regime

In recent years there has been a shift of interest in the Nanophotonics community moving from using metallic/plasmonic materials to using high-index dielectric materials for the construction of metasurfaces. Although high-index dielectrics hold many advantages over their plasmonic counterparts, the selection of materials that exhibit high-index properties, have low loss, and are complemetary metal-oxide-semiconductor (CMOS) compatible that also operate in the visible regime is extremely challenging. In this work, a high-index dielectric material using silicon rich nitride (SRN) is proposed and experimentally demonstrated as a platform for solving this problem. While SRN has been used before for diffractive lenses and structural colors, here its applicability for Huygens-type metasurfaces is focused upon. Specifically, a Huygens metasurface that operates in the visible range around a wavelength of 575 nm is theoretically and experimentally demonstrated, and the capabilities of spatially controlling the phase of this metasurface are further demonstrated by designing and fabricating a Huygens meta hologram. The study also shows that the refractive index can be controlled by the interplay between SiH₄ and NH₃ during the plasma-enhanced chemical vapor deposition (PECVD) process.