Light localization in 1D chirped photonic crystals

The features of the light localization and absorption in 1D harmonic chirped photonic crystals (PCs) were investigated. It was shown that although chirping leads to a loss of perfect periodicity, the integral over a wide spectral region light energy density practically does not change. We investigate the peculiarities of the spectra of photonic density of states (PDOS) and compare these spectra to those of density of localized light energy at different laws of chirping. In the photonic band gap (PBG), the PDOS has equidistant peaks indicating the possible excitation of coupled modes in the PBG. However, as was shown by comparing the spectra of PDOS and density of light energy, not all coupled modes are excited in the PBG. We showed, that breaking ideal periodical structure (the chirping) not only can decrease the integral over a wide spectral region absorption, but also it can bring to increase in integral absorption in the PCs, and it depends on the form of chirping. Then we investigated the evolution of reflection spectra when the contrast of the chirping changes. We showed that mini zones of transmission due to Zener tunneling arise in the PBG at certain values of chirping contrast.