Optical metamaterials: Design, simulation and feedback from experimental characterization
Abstract
Artificially structured materials (metamaterials) demonstrating negative index of refraction have opened an entire area of research. Metamaterials are not limited to just negative index metamaterials, but could be extended to artificial magnetism, chirality, etc. Such materials extend the material properties, to beyond what is available in nature. This enables us to control and manipulate light in an unprecedented manner and creates an immense potential for applications. In this work, simulations tools were developed for the study and design of metamaterials. These tools were based on 3D Finite Difference Time Domain (FDTD) method and Spatial Harmonic Analysis (SHA). In addition to this, a commercial tool based on Finite Element Method was also used. The first negative index material at the optical range was demonstrated, which showed a refractive index of around –0.3 at the telecom wavelength of 1.5 μm. This was followed by the demonstration of a double negative material at the lowest wavelength till date. It showed a refractive index of –0.8 at a wavelength of 725 nm. The negative index material at the shortest wavelength was demonstrated at a wavelength of 710nm. It showed a refractive index of –0.6 at a wavelength of 710 nm. Structures with artificial negative magnetism were also demonstrated across the entire visible range up to a wavelength of 490 nm. Rigorous study was performed on the effect of roughness and size effects on the performance of the nanoscale structures that were used in the metamaterial prototypes. It was concluded that roughness decreases the quality factor of the resonances that are vital for the novel properties. Roughness affects only parts of the spectrum that are close to a resonance. The size effect increases the losses in the metal that makes up the structure and consequently decreases the quality factor of the resonances. Unlike roughness, the size effect does not show a wavelength dependence based on resonances. The parallel 3D FDTD solver was used to numerically study the local field response in semicontinuous metal films (SMFs). These solutions provide insight into the nature of the local field enhancements in SMFs.
Degree
Ph.D.
Advisors
Kildishev, Purdue University.
Subject Area
Electrical engineering|Optics
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