Localization of defect modes in cholesteric liquid crystals with disordered defect layers

Light localization can significantly enhance light-matter interactions, making it crucial for achieving low-threshold lasers. In this study, we investigate how the degree of disorder in the positions of defect layers affects the localization of defect modes in the cholesteric liquid crystal with multiple defect layers. Defect modes are inherently localized within the defect layers. But the modes exhibit an extended state throughout the periodic defect layers due to mode coupling between nearest-neighbor layers. As the degree of disorder increases, the defect-mode field redistributes. For the defect modes, the inverse participation ratio gradually increases, the effective mode width narrows, and the variability of the mode's center position increases. These changes indicate that the degree of localization of the defect modes gradually increases, potentially approaching Anderson localization. The defect modes undergo a second-stage localization transition, becoming more strongly localized. In addition, as the number of defect layers increases, the degree of localization strengthens, and the effective mode width continues to narrow. This study presents a unique system for investigating Anderson localization and is significant for the realization of low-threshold lasers.