Maximized chiroptical resonses in metasurfaces

Abstract

Maximizing chirality is of utmost importance for advancing chiral optical applications, where strong chiral responses are crucial for diverse fields such as enantioselective sensing, chiral quantum optics, and spin-selective photonic devices. Enhancing light-matter interactions is key to achieving such strong chiral responses, and this enhancement can be effectively realized by confining light within small volumes. Recently, dielectric metamaterials have emerged as a highly effective platform for manipulating optical responses in flat optics, owing to their unique ability to support high-Q resonances and versatile field manipulations. Specifically, chiral dielectric metamaterials are particularly promising for achieving compact and integrated photonic devices with tailored chiroptical functionalities. These advances open pathways to practical applications where ultra-narrowband and high-purity chiral emission are highly desirable. We aim to design chiral metasurfaces that maximize chiroptical responses through diverse optical mechanisms. By providing strong artificial chirality, chiral metasurfaces significantly enhance the capabilities of photonic devices. In particular, we explore two distinct approaches—extrinsic and intrinsic chirality—each addressing different aspects of chiral optical behavior.

1) Realization of extrinsic chiral emission in perovskite metacavities In the first part of this dissertation, we demonstrate circularly polarized light sources based on symmetry-broken perovskite metacavities and topological control of perovskite emission. This part presents a chiral light source utilizing thin-film perovskite metacavities composed of a metal mirror and a dielectric metasurface, which supports photonic eigenstates with a near-maximal chiral response. The designed metacavities achieve asymmetric electroluminescence with a high degree of circular polarization (DCP), making it well-suited for applications like circularly polarized LEDs and spin- selective photonic devices. Additionally, we exploit momentum space topology to control 2D perovskite emission in the strong coupling regime using the nature of bound states in the continuum (BICs). The combination of polaritonic BICs and 2D perovskite materials offers exceptional topological features and optical properties, making it a promising platform for active nanophotonic devices.

2) Approaches to achieve ultra-narrowband chiral metamaterial absorbers The second part of this dissertation focuses on the design of intrinsic chiral metamaterial absorbers with ultra-narrowband characteristics, which are highly desirable for enhancing various chiral interactions. Balancing the simplicity of design, high-Q resonances, and strong chirality is essential in designing chiral metamaterial absorbers. However, the experimental realization of ultra-narrowband absorbers with extreme chiral responses remains challenging. To address this, we propose designs that leverage Fabry–Pérot bound states in the continuums (FP BICs) and Brillouin zone folding-induced guided mode resonances (BZF-GMRs) to achieve high-Q chiral resonances. These approaches enable precise control over chiral light absorption, paving the way for efficient photonic devices that capitalize on narrowband chiral interactions.