Chiral effects in strongly coupled resonant metasurfaces with epsilon-near-zero guided modes
Phys. Rev. B 112, 035408 – Published 7 July, 2025
DOI: https://doi.org/10.1103/kjqf-szyp
Abstract
The introduction of optical chiral quasibound states in the continuum (QBICs) provides a promising perspective for manipulating light at the nanoscale. Their strong field enhancement together with their intrinsic low loss under dielectric conditions enable us to efficiently boost and control the chiral coupling. Recently, the large electric field localization and enhancement supported by the epsilon-near-zero (ENZ) modes have garnered significant attention for the realization of strong light-matter interactions. Here, we demonstrate an all-dielectric metasurface, which integrates a nanorod array lacking any point symmetry elements with an ultrathin ITO layer, achieving strong chiral QBIC-ENZ coupling with tunable coupling strength. A pronounced anticrossing behavior can be observed under specific circular polarization, revealing remarkable chiroptical characteristic hybridization. By employing the coupled oscillator model combined with near-field analysis, a Rabi splitting of up to 135.8 meV is confirmed. We also demonstrate that the coupling strength in the chiral hybrid system can be modulated by varying the ITO thickness, which shows an obvious increase with thickness and is accompanied by fine-tuned chiral responses of the hybrid polaritons. This work provides a paradigm for chiroptical coupling based on ENZ materials, which offers great potential for low-loss, high-compact chiral photonic devices and nonlinear applications.
