Metasurfaces for augmented reality applications

This work presents the results of designing metasurfaces operating in the visible range for augmented reality (AR) applications. Using the finite difference time domain (FDTD) method, a variety of reflective and transmissive metasurfaces were achieved, most of which exhibit high efficiency across the visible spectrum. All of the demonstrated structures are plasmonic metasurfaces incorporating gold (Au) nanoantennas placed on an insulator-metal stack to form a metal-insulator-metal architecture. In several designs, an epsilon near zero (ENZ) material, indium tin oxide (ITO), was integrated to enable tunability, either by controlling fabrication parameters or through external stimuli such as heat or electrical bias. A detailed simulation study was carried out to realize a high-efficiency transmissive meta-surface that operates in the visible range and exhibits polarization sensitivity. The optical spectra are described and explained in detail, showing that the gap surface plasmon (GSP) resonance red-shifts and strengthens with increasing spacer thickness and antenna length, varies in depth and position with changes in width and heights, and respond to coupling shift set by the period, while the ITO-silver stack provide additional control over loss and confinement. In addition, work was carried out to control the λ_ENZ of ITO films by varying the fabrication parameters during the sputtering process,enabling λ_ENZ tuning from 1130 nm to beyond 1700 nm and establishing an understanding of the link between deposition parameters — such as gas type and concentration and substrate temperature — and the optical response of the metasurface.