Geometric Influence on Optical Bistability and Local Field Enhancement in Core-Shell Nanocomposites

This work investigates the role of geometric shape in tuning the optical bistability (OB) and local field enhancement factor (LFEF) of metal-coated dielectric core-shell (CS) nanoinclusions embedded in nonlinear dielectric host matrices. Through quasi-static analysis and Drude-based modeling, the study reveals that spherical and cylindrical nanoinclusions exhibit distinct OB thresholds and LFEF behaviors depending on their radii, dielectric environments, and shape-induced plasmonic resonances. Spherical CS nanostructures display stronger OB responses and field confinement at lower thresholds than their cylindrical counterparts. Results show that increasing host permittivity significantly widens the OB region, while reducing nanoinclusion size enhances optical nonlinearity. This investigation underscores the sensitivity of nonlinear optical responses to geometry, shell thickness, and host environment, providing valuable insights for designing tunable photonic components, including switches and optical memory devices.