Bakunov M I, Shirokova A V, Kurnikov M A, Maslov A V
Opt Lett. 2021 Oct 1;46(19):4988-4991. doi: 10.1364/OL.437419.
Temporal discontinuity in the permittivity of a nondispersive dielectric (temporal boundary) is a conventional model for considering electromagnetic phenomena in dynamic materials and metamaterials. Here we apply a more general model of a Lorentz medium with the rapidly changing density of its structural elements (oscillators) or their resonant frequency to determine the realms of applicability of the conventional temporal boundary model. We demonstrate the dependence of the continuity conditions and the energy relations at a temporal boundary on the nonstationarity mechanism and the ratio between the rate of nonstationarity and the characteristic frequencies in the system.
非色散电介质介电常数的时间不连续性（时间边界）是用于考虑动态材料和超材料中电磁现象的传统模型。在此，我们应用一种更通用的洛伦兹介质模型，该模型中其结构元素（振子）的密度或其共振频率快速变化，以确定传统时间边界模型的适用范围。我们证明了时间边界处的连续性条件和能量关系取决于非平稳性机制以及系统中非平稳率与特征频率之间的比率。
