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arXiv · 2509.12843

Observation of Fully Flat Bands in a Photonic Dipolar Kagome Lattice

Han-Rong Xia·Ziyao Wang·Yunrui Wang·Zhen Gao·Meng Xiao
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Abstract

Flat bands, characterized by zero group velocity and strong energy localization, enable interaction-enhanced phenomena across both quantum and classical systems. Existing photonic flat-band implementations were limited to evanescent-wave systems, specific lattice symmetries, or complex supercell modulations. A simple, universal, and efficient approach to realizing flat bands without dedicated source excitation is to be explored. Here, inspired by geometrically frustrated configurations, we theoretically proposed and experimentally demonstrated threefold-degenerate flat bands by integrating orbital and rotational degrees of freedom in a photonic dipolar kagome lattice. By rotating the dipole orientation, the system exhibits a band flip transition at which point all bands achieve complete flatness and degeneracy across the entire Brillouin zone. In contrast to conventional s-orbital kagome lattices with only a single flat band, our approach flattens the entire band structure, eliminating dispersive modes and enabling compatibility with arbitrary excitations. These results establish a new mechanism for flat-band engineering, offering a tunable strategy for enhancing light-matter interactions and may have applications in compact photonic devices and energy-efficient information processing.

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Han-Rong Xia, Ziyao Wang, Yunrui Wang, Zhen Gao, Meng Xiao. 2025-09-16. Observation of Fully Flat Bands in a Photonic Dipolar Kagome Lattice. https://arxiv.org/abs/2509.12843

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