Propagation of electromagnetic waves through liquid crystals with defect-based interfaces.

We present a theoretical study of electromagnetic surface wave modes along a dielectric interface that includes a smecticliquid crystal-based layer, and a metallic layer. The liquid crystal layer has a twist defect and metallic inclusions. The system is modeled by Maxwell's equation and we propose a Maxwell-Garnett theory for the dielectric response of the liquid crystal layer. Surface waves satisfy a Marcuvitz-Schwinger system that we solve numerically in the liquid crystal region assuming continuous fields at interfaces. The inverse dispersion relation shows the existence of localized modes associated with defect-tuned resonances. Field distributions for the electric, magnetic, and Poynting vector components imply enhanced confinement near the defect region, with strong amplification at resonant frequencies and clear evidence of energy trapping. We also observe the existence of a region of negative group velocity in the dispersion relation and we evaluate the possibility of metamaterial behavior. The comparison between single-period and multi-period liquid crystal layers indicates that increasing the number of periods reinforces localization and mode stability. These results highlight the role of structural defects in tailoring light propagation through anisotropic composite waveguides and open perspectives for tunable photonic devices based on liquid crystals.