Local field enhancement of cylindrical core-shell nanoparticle composites in passive and active dielectric core

In this paper, we investigated how local field enhancement (LFE) and induced optical bistability (IOB) of cylindrical core-shell nanoparticle composites (NPCs) with passive and active dielectric cores were affected by the metal fraction (p), and dielectric constant of host matrix. We have determined the expressions of the electric potentials for cylindrical core-shell NPCs by solving Laplace’s equations in the quasi-static limit. The equation of IOB was derived from the equation of local field enhancement factor (LFEF) by incorporating Drude-Sommerfeld model into the expressions. The host dielectric and the dielectric of the core are interfaced with the metal shell. The LFEF significantly rises at two resonant frequencies with increasing p and dielectric constant in both passive and active dielectric core. The findings reveal that S-like peaks of IOB are created in both passive and active dielectric cores of cylindrical NPCs, no matter how p, and dielectric constant change or remain constant. In NPCs, both in passive and active dielectric cores, an increase in any of these parameters results in switching-up and switching-down threshold points where optical bistability (OB) resonances prevail. Within passive and active dielectric cores, increasing p shows the incident field required at each switching-up threshold point also increases and the bistable region produced gets wider. Additionally, it was found that the bistable area of the IOB in active dielectric cores of cylindrical core-shell NPCs is reduced when the host dielectric constant increases.