Experimental observation of exceptional bound states in the continuum

@misc{wu2026experimental,
  title = {{Experimental observation of exceptional bound states in the continuum}},
  author = {Shuang Wu and Ruizhi Dong and Nikolay Solodovchenko and Dongxing Mao and Andrey Bogdanov and Yong Li},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.13086},
  eprint = {2609.13086},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.13086},
}

TY  - UNPB
TI  - Experimental observation of exceptional bound states in the continuum
AU  - Shuang Wu
AU  - Ruizhi Dong
AU  - Nikolay Solodovchenko
AU  - Dongxing Mao
AU  - Andrey Bogdanov
AU  - Yong Li
PY  - 2026
DA  - 2026/09/11
PB  - arXiv
DO  - 10.48550/arxiv.2609.13086
UR  - https://arxiv.org/abs/2609.13086
AB  - We experimentally demonstrate second- and third-order exceptional bound states in the continuum (EP-BICs), formed by the merging of two and three symmetry-protected BICs at an exceptional point (EP). Our passive reciprocal acoustic platform consists of symmetry-protected BIC cavities coupled through an acoustic waveguide and enables independent control of intrinsic loss, radiative loss, and near-field coupling between the cavities. A nonuniformly distributed intrinsic loss provides the non-Hermiticity required for EP formation while preserving decoupling from the waveguide radiation channel. The EP-BICs are probed using both near- and far-field excitation. In the near field, local intracavity excitation directly accesses the symmetry-protected BICs and reveals their spectral evolution. For far-field excitation, we intentionally break the protecting geometrical symmetry, converting the BICs into quasi-BICs and making them accessible through transmission measurements. Extending the system to three cavities with graded intrinsic loss realizes a third-order EP-BIC and yields a larger spectral response to the implemented coupling perturbation. These results establish a passive reciprocal route to higher-order exceptional degeneracies with independent control over intrinsic loss, near-field coupling, and radiative access.
ER  -