Ellipsometric Identification of Transition from Layered Metal-dielectric Film to Hyperbolic Metamaterial

Hyperbolic Metamaterials (HMMs) continue to be intriguing due to their applications in super resolution imaging and spontaneous emission control. One of the successful realizations of HMMs is a layered metal-dielectric film. Despite the extensive knowledge in thin film technology and the promises of HMM's applications, the scale up and practical utilization of HMMs have not yet occurred. This is due to the difficulty in identifying versatile design parameters for HMM fabrication and characterization via accessible techniques. In this work, spectroscopic ellipsometry and numerical simulations are utilized to identify design parameters for fabrication of HMMs using the silver and alumina system as a model system. Four interdependent design parameters are explored: thicknesses of metal and dielectric layers, transition wavelength, and minimum number of periods required for a layered metal-dielectric film to display hyperbolic dispersion. The findings are presented as a practical engineering design chart.