Control and quantification of near-field electromagnetics

This thesis explores the intricate interactions between electromagnetic fields and matter across both optical and magnetic near-field regimes, revealing applications and theoretical advancements in nanophotonics, near-field microscopy, magnetic resonance imaging (MRI), and wireless power transfer (WPT). The investigation is bifurcated into two pivotal areas: the optical near-field effects facilitated by plasmonic nanostructures and the manipulation of magnetic near-fields through metamaterials. In the optical domain, the research delves into the near-field profiles of plasmonic nanostructures, with a particular focus on gold nanorods as anisotropic exemplars. It unveils how the near-field spatial profile is influenced by the nanostructures' sizes, geometries, and the laser pulse durations. The thesis demonstrates the manipulation of near-field photoacoustic profiles through anisotropic spatial arrangements of isotropic gold nanostructures, showcasing applications in enhancing enantioselective absorptions and understanding the interaction between gradient fields and electric quadrupoles. The study further addresses the challenge of decoupling optical forces—a critical step for advancing our comprehension of light-matter interactions and their applications in sensing, imaging, and actuation. A decoupled optical force nanoscopy (Dofn) system is introduced, capable of mapping piconewton-level optical force components with unprecedented resolution. This system facilitates an ultrafast visualization of dynamic heat transfer, which enables charaterization of photothermal dynamics at the nanoscale. Transitioning to the radiofrequency regime, the thesis presents a theory of magnetic metasurfaces for on-demand field shaping, a new method in controlling magnetic near-fields. This approach enables the enhancement of signal-to-noise ratios in MRI and the efficiency of WPT systems, offering a robust solution for wearable devices and multi-receiver charging systems. The metasurface's design allows for the manipulation of not only the intensity but also the orientation of non-radiative magnetic fields, showcasing its versatility and potential for high efficiency, free-positioning, and multi-user compatible power transfer. Last but not least, this thesis extends the application of metamaterials to control parity-time (PT) symmetry in WPT systems, facilitating new designs for multibody WPT systems through fine-tuned coupling coefficients. PT-symmetry phase could be achieved even with unsymmetrically placed and sized transmitter and receiver. This approach underscores the potential of metamaterials in transcending traditional limitations in multibody WPT systems, particularly with relay resonators. This comprehensive study bridges the gap in our understanding of near-field interactions and introduces methodologies and applications in the realms of nanophotonics, materials science, and electronics. Through a meticulous investigation of optical and magnetic near-fields, this thesis not only advances our theoretical knowledge but also paves the way for practical applications in sensing, medical imaging, and wireless power transfer.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Electrical & Computer Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2024

Author dc:creator

• Wang, Hanwei

Contributors dc:contributor

• Zhao, Yang
• Cunningham, Brian T
• Gruev, Viktor
• Jin, Jianming
• Chen, Yun-Sheng

• Nanophotonics
• Plasmonic Nanostructures
• Light-matter Interactions
• Magnetic Metasurfaces
• Wireless Power Transfer

Statement dc:rights

• Copyright 2024 Hanwei Wang

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/124705

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F124705