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

TL;DR

This paper develops a practical design chart using ellipsometry to identify the transition from layered metal-dielectric films to hyperbolic metamaterials, aiding scalable fabrication.

Contribution

It combines effective medium approximation and transfer matrix method to predict the transition, validated by spectroscopic ellipsometry, providing a useful engineering tool.

Findings

Validated transition prediction with ellipsometry

Identified key parameters influencing hyperbolic dispersion

Provided a design chart for practical HMM fabrication

Abstract

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. A general design approach is needed to predict the transition of a layered structure into an HMM. In this work, effective medium approximation and transfer matrix method are combined to determine the transition and validated by spectroscopic ellipsometry measurements on a predefined HMM structure made of silver and alumina. 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, similar to a state diagram, that can be extended to other combinations of materials.