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arXiv · 2401.03165

Non-orthogonal cavity modes near exceptional points in the far field

Jingnan Yang·Shushu Shi·Sai Yan·Rui Zhu·Xiaoming Zhao·Yi Qin·Bowen Fu·Xiqing Chen·Hancong Li·Zhanchun Zuo·Kuijuan Jin·Qihuang Gong·Xiulai Xu
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Abstract

Non-orthogonal eigenstates are a fundamental feature of non-Hermitian systems and are accompanied by the emergence of nontrivial features. However, the platforms to explore non-Hermitian mode couplings mainly measure near-field effects, and the far-field behaviour remain mostly unexplored. Here, we study how a microcavity with non-Hermitian mode coupling exhibits eigenstate non-orthogonality by investigating the spatial field and the far-field polarization of cavity modes. The non-Hermiticity arises from asymmetric backscattering, which is controlled by integrating two scatterers of different size and location into a microdisk. We observe that the spatial field overlaps of two modes increases abruptly to its maximum value, whilst different far-field elliptical polarizations of two modes coalesce when approaching an exceptional point. We demonstrate such features experimentally by measuring the far-field polarization from the fabricated microdisks. Our work reveals the non-orthogonality in the far-field degree of freedom, and the integrability of the microdisks paves a way to integrate more non-Hermitian optical properties into nanophotonic systems.

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Jingnan Yang, Shushu Shi, Sai Yan, Rui Zhu, Xiaoming Zhao, Yi Qin, Bowen Fu, Xiqing Chen, Hancong Li, Zhanchun Zuo, Kuijuan Jin, Qihuang Gong, Xiulai Xu. 2024-01-06. Non-orthogonal cavity modes near exceptional points in the far field. https://doi.org/10.1038/s42005-023-01508-2

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