Study Demonstrates Impact of Mode Completeness on Quasinormal Mode Coupling Theory Accuracy
Researchers have provided a strict numerical demonstration showing that using a virtually complete basis of regularized quasinormal modes (RQNMs) enables the quasinormal mode coupling theory (QCT) to accurately predict both source-free eigenmodes and source-excited scattered fields in coupled optical nanoresonator systems. The work addresses a longstanding gap in the field, as quasinormal modes diverge exponentially in the far field and cannot form a complete basis outside a resonator without regularization. The findings confirm that incomplete, non-regularized quasinormal modes yield poor accuracy, underscoring the necessity of regularization methods for practical nanophotonic modeling.
A new preprint on arXiv presents a rigorous numerical demonstration of how mode completeness affects the accuracy of quasinormal mode coupling theory (QCT) for coupled lossy and dispersive optical nanoresonators. Quasinormal modes (QNMs) are a key theoretical tool in nanophotonics, but they suffer from exponential divergence in the far field, preventing them from forming a complete basis outside the resonator without additional treatment. The authors employ two regularization strategies—equivalent surface current (ESC-RQNMs) and perfectly matched layer (PML-RQNMs)—to obtain regularized QNMs that can span the field both inside and outside the resonator. Using a test case of two one-dimensional slab resonators in direct contact (an extreme coupling scenario), the study demonstrates that a virtually complete RQNM basis allows QCT to accurately reproduce coupled system eigenmodes and scattered fields, while incomplete physical QNM bases fail to do so. The paper also introduces improvements to the QCT formulation and provides theoretical demonstrations of how RQNMs can be rigorously incorporated into the coupling framework. The work builds on a previously established first-principles QCT framework and aims to make the approach computationally efficient and physically intuitive for nanophotonic design.
What's missing
The study is limited to a one-dimensional slab geometry chosen for analytical tractability; it remains an open question how well the conclusions generalize to three-dimensional or more complex nanoresonator geometries.
What different sources said
- arXiv physicsCenter
Impact of mode completeness on the accuracy of the coupling theory of quasinormal modes: a strict numerical demonstration
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