连续谱中奇异束缚态的实验观测
Experimental observation of exceptional bound states in the continuum
- Tongji University（同济大学）
- ITMO University（ITMO大学）
- Harbin Engineering University（哈尔滨工程大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本文实验演示了连续谱中的二阶和三阶奇异束缚态，通过非均匀固有损耗实现非厄米性，并独立控制损耗与耦合，为高阶奇异简并提供了无源互易途径。
AI中文摘要：
我们在实验上演示了连续谱中的二阶和三阶奇异束缚态（EP-BICs），它们由两个和三个对称性保护的BIC在奇异点（EP）处合并形成。我们的无源互易声学平台由通过声波导耦合的对称性保护BIC腔体组成，能够独立控制腔体间的固有损耗、辐射损耗和近场耦合。非均匀分布的固有损耗提供了形成EP所需的非厄米性，同时保持与波导辐射通道的解耦。EP-BICs通过近场和远场激发进行探测。在近场中，局部腔内激发直接访问对称性保护的BICs并揭示其光谱演化。对于远场激发，我们有意破坏保护性几何对称性，将BICs转换为准BICs，使其可通过透射测量访问。将系统扩展到具有梯度固有损耗的三个腔体，实现了三阶EP-BIC，并对所实施的耦合扰动产生更大的光谱响应。这些结果建立了一条无源互易路径，以实现具有独立控制固有损耗、近场耦合和辐射访问的高阶奇异简并。
英文摘要：
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.
