Observation of an accidental bound state in the continuum in a chain of dielectric disks

TL;DR

This paper reports the first experimental observation of an accidental bound state in the continuum in a one-dimensional chain of dielectric disks, demonstrating its properties and potential for practical applications in radio-frequency and optical devices.

Contribution

It presents the first experimental observation of an accidental electromagnetic BIC in a dielectric disk chain, with analysis of its properties and implications for device development.

Findings

Accidental BIC observed as a narrow transmission peak.

Radiative quality factor grows linearly with the number of disks.

Near-field measurements confirm the BIC profile.

Abstract

Being a general wave phenomenon, bound states in the continuum (BICs) appear in acoustic, hydrodynamic, and photonic systems of various dimensionalities. Here, we report the first experimental observation of an accidental electromagnetic BIC in a one-dimensional periodic chain of coaxial ceramic disks. We show that the accidental BIC manifests itself as a narrow peak in the transmission spectra of the chain placed between two loop antennas. We demonstrate a linear growth of the radiative quality factor of the BICs with the number of disks that is well-described with a tight-binding model. We estimate the number of the disks when the radiation losses become negligible in comparison to material absorption and, therefore, the chain can be considered practically as infinite. The presented analysis is supported by near-field measurements of the BIC profile. The obtained results provide useful guidelines for practical implementations of structures with BICs opening new horizons for the development of radio-frequency and optical metadevices.