Browsing by Author "Taylor, Zachary, Prof., Aalto University, Department of Electronics and Nanoengineering, Finland"
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- Curved boundary integral method and its application to Mie theory: Electromagnetic beam synthesis and scattering analysis
School of Electrical Engineering | Doctoral dissertation (article-based)(2024) Lamberg, JoelThis doctoral thesis presents the development and application of the curved boundary integral method (CBIM) in conjunction with Mie Theory to enhance electromagnetic beam synthesis and scattering analysis, focusing on terahertz (THz) corneal imaging. This research adapts the proposed CBIM to model the interactions of electromagnetic beams with the human eye, aiming to advance non-invasive imaging techniques for the early detection of ocular diseases. The presented theories are scalable to any classical electromagnetism frequency range. The thesis introduces the CBIM, a sophisticated method and computational tool for synthesizing electromagnetic fields from arbitrary source field distributions on compact and regular surfaces. This method approximates beam synthesis using only electric field distributions, neglecting magnetic ones, which is accurate for surfaces with radii of curvature larger than a few wavelengths. The presented method allows precisely manipulating beam properties such as wavefront, amplitude, phase, and polarization directly from the source surface. Subsequently, Mie scattering theory is integrated into the analysis by extending CBIM into a source-free, basis-function based 3D angular spectrum method, enabling synthesized beams to be expanded into vector spherical harmonics. These theoretical advancements enhance electromagnetic field applications in biomedical contexts, particularly within the 0.1-1 THz range, which is well-suited for penetrating 0.5 mm into the human cornea. Simulations and theoretical analyses demonstrate the high accuracy and effectiveness of the CBIM, its extension to the 3D angular spectrum method, and its applications in Mie scattering theory. These methods show potential in biomedical applications and optical engineering. This thesis further explores the application of this methodology in THz corneal spectroscopy, illustrating how wavefront-modified and polarization-optimized vector beams can significantly reduce errors associated with traditional Gaussian beam analysis. Findings could improve the diagnostic capabilities of THz imaging technologies in clinical settings. This work significantly advances the theoretical framework of electromagnetic beam synthesis using CBIM and its modification to the 3D angular spectrum method. It allows for free manipulation of the incident field by its wavefront, amplitude, phase, and polarization distribution, showcasing the practical implications of these methods in enhancing the resolution and diagnostic accuracy of THz corneal spectroscopy and contributing significantly to the early detection and monitoring of ocular diseases.