arXiv subjects

Zhichun Qi

Publications and source records attributed to Zhichun Qi.

2 recordsLinked to original sources

arXiv2026

Fabry-Pérot Metacavities with Single-Layered Dielectric Metamirrors

The Fabry-Pérot resonator is a cornerstone of photonics and wave physics, providing a universal mechanism for spectral confinement and resonant enhancement of wave-matter interactions. In this work, we establish an analytically tractable class of Fabry-Pérot metacavities in which the reflecting elements are realized by single-layer periodic arrays of circular dielectric cylinders acting as metamirrors. Both the reflection efficiency and reflection phase of such metamirrors are obtained in closed form and shown to be widely and independently tunable, encompassing ideal electric and magnetic mirror limits with unit reflectivity. Building on these results, we derive explicit analytical expressions that fully describe the optical responses of Fabry-Pérot cavities composed of two such parallel metamirrors. Our combined analytical and numerical investigations reveal that these metamirrors provide exceptional flexibility for tailoring Fabry-Pérot resonances across a broad spectral range, enabling precise control over resonance positions and quality factors. In particular, the framework naturally predicts the emergence of Fabry-Pérot bound states in the continuum with formally infinite Q-factors. These results establish dielectric-metamirror-based Fabry-Pérot cavities as a versatile and fundamentally transparent platform for engineering high-Q optical resonances.

physics.optics↗

arXiv2025

Polarization-Independent Zero Directional Scattering Without Geometric Symmetries

As the characteristic feature of generalized Kerker effect in Mie theory, directional scattering elimination has been playing a pivotal role in nanophotonics and many other photonic disciplines, such as singular optics and topological photonics. Generally, zero directional scattering can be obtained only for a specific incident polarization, and to make it fully independent of arbitrary polarizations would require scatterers that exhibit geometric (\textit{e.g.} mirror) symmetries. Here we revisit the generalized Kerker effect and directional scattering elimination from the perspective of not the conventional electromagnetic multipoles, but rather quasi-normal modes supported by non-Hermitian systems. We reveal how to obtain zero directional scattering that is independent of arbitrary incident polarizations, even for scattering structures that do not exhibit the required geometric symmetries. Such geometric symmetry-free and polarization-independent responses are made accessible through a synchronous exploitation of electromagnetic reciprocity and geometric phase. Our discovery can stimulate fundamental explorations and practical applications in not only photonics, but also many other wave physics branches where scattering and geometric phase are pervasive.

physics.optics↗