Chiral Light–Matter Interactions Across Length Scales

Chiral light-matter interactions underpin the spectroscopic characterization of chiral molecular systems and are central to prospective all-optical implementations of enantioselective applications in chemistry and pharmacology. This dissertation develops and applies theoretical and numerical methods to describe chiral light-matter interactions across length scales, from microscopic scatterers to macroscopic photonic structures, and in particular uses them to design a highly helicity-biased chiral optical cavity.

As a theoretical foundation, we formulate linear optical media via constitutive relations, discussing in particular the magnetic-electric cross-coupling characterizing chirality, and we express electromagnetic waves in terms of helicity eigenfunctions. Combining these formulations, we employ transition and scattering matrix formalisms for chiral light-matter interactions with localized and planar systems, respectively, including analytic expressions for spherical scatterers and planar interfaces between chiral media.

Utilizing these formalisms, we investigate how different manifestations of chirality contribute to the overall optical response. ... mehrFor finite scatterers with chiral geometries and composed of chiral media, we show that circular dichroism can be decomposed, to an excellent approximation, into separate material and geometric contributions. We exploit the smallness of typical material chirality parameters to devise an efficient approximation scheme for chirality-dependent transition matrices and derived spectroscopic quantities. For chiral arrangements of achiral plasmonic nanoparticles, we demonstrate strongly enhanced, bisignate circular dichroism arising from the coupling between the particles and analyze the role of higher multipoles in accurate modeling.

Finally, we optimize an electromagnetically chiral silver helix, reaching 95 % of the ideal helicity selectivity, and use arrays of such helices to realize a chiral optical cavity that supports eigenmodes of nearly pure helicity and exhibits a helicity-selective contrast in resonant intensity enhancement of three orders of magnitude. The resulting dissymmetry of up to 94 % illustrates how microscopic chiral building blocks can imprint their response onto macroscopic devices, providing a chiral electromagnetic environment suitable for future enantioselective optical applications.