Design and Characterization of Optical Metamaterials Using Tunable Polarimetric Scatterometry Dissertation

Optical metamaterials are a class of engineered materials with a wide range of material properties and an equally wide range of anticipated applications. These materials traditionally attain their unique material properties from unit cell structures or material layers which are periodically arranged. These periodic structures are often described using effective medium theory (EMT), which is believed to remain valid so long as the EMT description of the material is applied under long wavelength conditions (i.e. where the incident wavelength can be assumed much larger than the unit cell or period dimensions). This condition is increasingly difficult to achieve at optical wavelengths. This problem was singled-out for negative refractive index materials, but they are not the only optical metamaterial violating these dimensional constraints. One of the simplest optical metamaterial structures was also found to be violating these constraints-a periodic layered metal-dielectric structure used to attain near-zero permittivity at a visible wavelength. In this research, a set of four periodic near-zero permittivity structures was developed. A transfer matrix method (TMM) model was found to accurately predict the experimental behavior of these structures but EMT did not. Additional modeling work was completed to demonstrate the dimensional constraints necessary for EMT predictions to match the predictions of a trusted and verified TMM model and establish a foundation for future near-zero permittivity designs. Of additional concern in metamaterials research, theoretical predictions for metamaterials have been shown to have incident angle and incident polarization state dependencies. Furthermore, these properties are narrow-band in nature. To date, optical AFIT-ENP-DS-12-03 v metamaterials have not been subjected to full-directional, full-polarimetric characterization because there has yet to be an instrument developed with the spectral range and full-directional, full-polarimetric capabilities needed to carry out this work. This research work also addressed the instrument/characterization void in optical metamaterials research. A tunable infrared (IR) Mueller matrix (Mm) polarimeter-scatterometer was developed and operates with a fully optimized dual-rotating retarder having 1/3 wavelength achromatic retarders. After developing this instrument, it was used to measure the polarimetric behavior of an infrared metamaterial absorber (MMA) at 5.0µm. This is the first spectral, fully polarimetric and fully directional characterization reported for an optical metamaterial. The extracted Mm for this sample was found to have incident angle dependence which did not follow isotropic or anisotropic Fresnel reflectance behavior. However, the experimentally retrieved Mm is valid and was used to predict the reflected polarimetric behavior of the MMA when canonical polarization …