Graduation Semester and Year
Spring 2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Electrical Engineering
Department
Electrical Engineering
First Advisor
Robert Magnusson
Abstract
The advent of diffraction gratings with periodic unit cells has led to numerous advancements in theoretical studies and practical applications. Recently, these structures have been recognized as subsets of “meta-surfaces” or “meta-materials”, employing periodically aligned features at the wavelength scale to manipulate electromagnetic wave properties for diverse applications. This manipulation extends to controlling amplitude, phase, spectral distribution, polarization state, and the local mode structure of light across various spectral expressions. A significant characteristic of these metasurfaces is their ability to couple incident light to laterally propagating leaky Bloch modes in the subwavelength regime, resulting in resonance at specific wavelengths known as “guided mode resonance (GMR)” or “leaky mode resonance (LMR)”. These structures offer unique functionalities in ultra-thin device dimensions, making them potential replacements for conventional and bulkier optical devices.
Extensive research has explored the fabrication of periodic structures in different materials, utilizing various methods for different wavelength ranges in 1D or 2D configurations. The diverse material compositions and lattice architectures contribute to the vast design space in this field.
Numerical techniques, including rigorous coupled-wave analysis (RCWA), finite element method (FEM), and finite-difference time-domain (FDTD), are utilized for simulations to obtain precise optical responses of metasurfaces. Additionally, inverse optimization methods efficiently provide optimized physical parameters to achieve specific spectral responses. However, these computational methods, while solving complex equations, may not always offer comprehensive insight into the underlying physics of numerically obtained optical spectra.
This dissertation combines theoretical and experimental investigations into innovative metasurfaces based on Guided-Mode Resonance (GMR). The research employs a diverse toolkit of design and simulation tools, micro and nano patterning techniques, thin film deposition methods, and etching procedures, complemented by optical and structural characterization techniques such as ellipsometry, SEM, AFM, and OSA, to develop the content presented in subsequent chapters.
We provide a comprehensive exploration of resonant photonic lattices, revealing fundamental physics and practical applications. The theoretical foundation, centered on evanescent-wave-induced leaky Bloch modes, challenges conventional views on the influence of local particle resonance. The study demonstrates that perfect reflection is primarily governed by the lattice period. Building on this, spectral properties of resonance reflection in 2D arrays are investigated, emphasizing the elimination of Mie resonance for persistent perfect reflection.
Exploring innovative concepts like “band flip" in one-dimensional dielectric lattices, the research measures the behavior of leaky bands, offering insights into the impact of fill factor variation. Additionally, the exploration of multiple simultaneous bands in subwavelength structures and the influence of interface modifications contribute to practical applications such as optical filters and sensors.
The dissertation also pioneers a departure from prior limitations by scrutinizing Rytov’s Effective Medium Theory under off-normal angles, enriching the understanding of complex interactions within resonant photonic lattices. Finally, the impact of finite beam size and lattice periods on performance is assessed, considering finite-sized beams and lattices. This work provides valuable contributions to the design and optimization of photonic lattices, offering insights for applications in optical filters, sensors, and resonance-based technologies.
Keywords
Nanophotonics, Metasurface, Diffraction optics, Nano-Micro Fabrication, Guided mode resonance
Disciplines
Electromagnetics and Photonics | Nanotechnology Fabrication
License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Recommended Citation
Razmjooei, Nasrin, "A Comprehensive Exploration of Fundamental and Experimental Characteristics of Nanophotonic Metasurfaces" (2024). Electrical Engineering Dissertations. 2.
https://mavmatrix.uta.edu/electricaleng_dissertations/2