AI 中文总结
研究反射衬底上均匀有损层的完美电磁吸收条件，通过相量图分析及时间耦合模理论，发现接近n = 1的中间区域情况有根本变化，此临界阻尼状态能驱动光谱展宽并瞬间耗散超短脉冲，将品质因数最小化到Q≈0.69。
AI 中文摘要
我们重新审视了反射衬底上均匀有损层中实现完美电磁吸收的条件。通过相量图分析，我们证明了高折射率极限（经典达伦巴赫四分之一波长吸收器）和近零介电常数区域（半波长共振）之间存在基本的物理相似性。在这两种极端情况下，完美吸收都依赖于长循环多径传播和逐渐的幅度衰减。关键的是，我们发现，在接近n = 1的中间区域，情况发生了根本变化：俘获效率急剧增加，并且在单次往返中几乎瞬间消除了反向散射。使用时间耦合模理论，我们证明这种低对比度状态将系统的品质因数最小化到全局最小值Q≈0.69。这种临界阻尼状态反映了声学和力学中普遍存在的高阻尼稳定原理，驱动异常光谱展宽，并能够几乎瞬间耗散超短脉冲而没有时域振铃。
英文摘要
We revisit the conditions for perfect electromagnetic absorption in a homogeneous lossy layer on a reflecting substrate. Using phasor diagram analysis, we demonstrate a fundamental physical similarity between the high-refractive-index limit (classic Dallenbach quarter-wavelength absorbers) and the epsilon-near-zero regime (half-wavelength resonances). In both extremes, perfect absorption relies on long cyclic multipath propagation and gradual amplitude decay. Crucially, we uncover that in the intermediate regime near $n = 1$, this picture changes fundamentally: the trapping efficiency drastically increases, and backscattering is eliminated almost instantaneously within a single round-trip. Using temporal coupled-mode theory, we prove that this low-contrast state minimizes the system's quality factor to a global minimum of $Q \approx 0.69$. This critically damped state mirrors universal highly damped stabilization principles found in acoustics and mechanics, driving anomalous spectral broadening and enabling nearly instantaneous dissipation of ultrashort pulses without time-domain ringing.
