3thInternational Congress of Engineering and Natural Sciences Studies, Ankara, Turkey, 24 - 25 May 2023, pp.110
Noble metals such as gold and silver used in plasmonic applications possess significant optical losses. Instead of these, alternative plasmonic materials such as doped silicon, doped germanium, and transition metal nitrides, whose plasma frequency can be controlled due to their low cost and tunable electron number, can be used. Titanium nitride, one of the transition metal nitrides, exhibits metallic properties with plasmonic behavior at visible and near-infrared wavelengths. In this context, eight types of aperture-based nanoantenna designs that provide resonative light transmission and form a full-phase transition are presented. A multifocal alternative plasmonic metalens design is proposed in which these nanoantennas form unit cells. The unit cells are constructed in aperiodic arrangement and circular rings, in such a way that they provide a full phase transition from the center of the metalens in the radial direction. The focusing behavior of the designed structure at 850 nm, which is one of the fiber optical wavelengths, is analyzed theoretically. Field distributions with multifocal points are presented in line with the theoretical analysis facilities. The focusing performance of this multifocal structure was determined by theoretical data such as focal spot width, numerical aperture, focal length, focal depth, and focusing efficiency.
Keywords: Multifocal metalens, alternative plasmonic, focusing performance, circular phase distribution, nanoapertures