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arXiv · 2505.17444

Experimental Study of Fabry-Perot BICs in a Microwave Waveguide

Zilong Zhao·Nikolay Solodovchenko·Chao Sun·Mingzhao Song·Ekaterina Maslova·Andrey Bogdanov
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Abstract

We study Fabry-Perot bound states in the continuum (FP-BIC) in the GHz frequency range, formed by two ceramic discs placed inside a metallic-walled rectangular waveguide, that act as perfect reflectors at the resonant frequency. The energy becomes perfectly trapped between the discs, forming a FP-BIC, when the distance between them matches the Fabry-Perot quantization condition. We present both theoretical and experimental analyses to investigate how the total and radiative quality factors (Q factors) depend on the inter-disk distance. We gain valuable insights into the Fano features observed in the transmission spectra using the quasi-normal mode technique and temporal coupled mode theory. Notably, we find that as the system approaches the BICs, the Fano asymmetry parameters diverge, resulting in a Lorentzian transmission profile. Experimentally, we measure a radiative Q factor on the order of $10^5$, while the total Q factor, limited by material losses, remains around $10^3$. These results offer new opportunities for the application of BICs in microwave technology, significantly advancing the potential for high-performance devices.

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Zilong Zhao, Nikolay Solodovchenko, Chao Sun, Mingzhao Song, Ekaterina Maslova, Andrey Bogdanov. 2025-05-23. Experimental Study of Fabry-Perot BICs in a Microwave Waveguide. https://doi.org/10.1063/5.0285583

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