Optical spin, optical helicity, and light-matter interactions

Butler, Benjamin William (2025) Optical spin, optical helicity, and light-matter interactions. PhD thesis, University of Glasgow.

Abstract

Over the past three decades, a tremendous amount of research has been dedicated to the theoretical analysis and experimental realization of structured forms of light—optical fields with complex structures in their phase, polarization, or other degrees of freedom. Beyond their inherent optical properties, which are often interesting and unexpected compared to simpler, unstructured fields, structured light fields also give rise to novel effects when interacting with matter. In this Thesis, I examine some fundamental and practical aspects of the angular momentum and chirality of light, two key topics in modern structured light research. My focus is on the optical spin angular momentum and the optical helicity in monochromatic fields. Regarding the former, I examine the local spin in non-interfering superpositions of plane waves. Amongst other intriguing features, the electric and magnetic spins—which are distinct physical contributions to the total optical spin—show striking differences in these fields, and I discuss the implications of these spin structures on light-matter interactions. In connection with the optical helicity, I develop a theoretical model for the transfer of helicity from a monochromatic optical field to a single atom, shedding greater light on the fundamental role of helicity in light-matter interactions. I also present two derivations—one of the Faraday effect in a gas, the other of the helicity-dependent chiroptical force—within the framework of molecular quantum electrodynamics, opening the door to future explorations of structured light-matter interactions from the fundamental photonic perspective.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QC Physics
• Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
• Funder's Name: Engineering and Physical Sciences Research Council (EPSRC)
• Supervisor's Name: Goette, Professor Joerg
• Date of Award: 2025
• Depositing User: Theses Team
• Unique ID: glathesis:2025-85183
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 12 Jun 2025 14:23
• Last Modified: 12 Jun 2025 14:25
• Thesis DOI: 10.5525/gla.thesis.85183
• URI: https://theses.gla.ac.uk/id/eprint/85183