Absorption and Light Localization in One-Dimensional Apodized Photonic Crystals

Apodization is a well-known method designed to control the propagation of light in photonic crystals (PCs) and has a variety of applications. Apodization involves modulating the depth of refractive index variation in PCs. In this work, we considered harmonic PCs with different forms of linear apodization. We investigated the characteristics of reflection, absorption, photonic density of states (PDOS), and light energy density spectra in the PC. For the first time, it was shown that apodization significantly reduces the PDOSs at the first edge modes, while its influence on higher-order edge modes is considerably weaker. Depending on the apodization profile, the spectral density of integral absorption can either substantially increase or decrease, and, moreover, in large intervals. We also studied the evolution of light localization in the PC, both in the presence and in the absence of apodization. One of the central and most significant claims in our paper is the demonstration of a divergence between integral absorption and total localized light energy. Our results demonstrate that apodization leads to a reduction in the total integral light energy localized within the PC layer.