The vacuum Rabi splitting (VRS) in molecular polaritons stands as a fundamental measure of collective light–matter coupling. Despite its significance, the impact of molecular disorder on VRS is not fully understood yet. This study delves into the complexities of VRS amidst various distributions and degrees of disorder. Our analysis provides precise analytical expressions for linear absorption, transmission, and reflection spectra, along with a “sum” rule, offering a straightforward protocol for extracting accurate collective light–matter coupling values from experimental data. Importantly, our study cautions against directly translating large VRS to the onset of ultrastrong coupling regime. Furthermore, for rectangular disorder, we witness the emergence of narrow side bands alongside a broad central peak, indicating an extended coherence lifetime even in the presence of substantial disorder. These findings not only enhance our understanding of VRS in disordered molecular systems but also open avenues for achieving prolonged coherence lifetimes between the cavity and molecules via the interplay of collective coupling and disorder.

中文翻译：

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从无序极化子中提取准确的光-物质耦合

分子极化子中的真空拉比分裂（VRS）是集体光-物质耦合的基本测量方法。尽管具有重要意义，但分子紊乱对 VRS 的影响尚未完全了解。这项研究深入探讨了 VRS 在不同分布和无序程度下的复杂性。我们的分析提供了线性吸收、透射和反射光谱的精确分析表达式，以及“求和”规则，为从实验数据中提取准确的集体光-物质耦合值提供了一个简单的协议。重要的是，我们的研究警告不要直接将大 VRS 转化为超强耦合状态的开始。此外，对于矩形无序，我们看到在宽的中心峰旁边出现窄边带，这表明即使存在大量无序，相干寿命也延长。这些发现不仅增强了我们对无序分子系统中 VRS 的理解，而且还为通过集体耦合和无序的相互作用实现腔和分子之间延长相干寿命开辟了途径。