Tunable polarization-sensitive optical nanoswitches based on spheroidal core-shell nanoparticles

Abstract

In this paper, we suggest the design of wavelength tunable, polarization-sensitive optical nanoswitches based on plasmonic spheroidal core–shell nanoparticles. Using a quasi-static approximation, we derive closed-form expressions for short and open circuit conditions, which respectively provide extremely high and low permittivity values at optical frequencies. Owing to the anisotropic nature of spheroidal particles, the analysis are performed in longitudinal and transversal polarizations, where the electric field of the impinging wave is along the major and minor axes of the spheroid, respectively. The derived formulas analytically elucidate this anisotropy, which has been implied by different short and open circuit conditions for two states of polarization. Our results show that by exploiting eccentricity in the spheroidal core–shells (i.e. compared to the spherical core–shells), the switching conditions can be transferred to infrared (IR) and ultraviolet (UV) frequencies, in longitudinal and transversal polarizations, respectively. Finally, the effective permittivity of the core–shell is extracted analytically using the concept of internal homogenization, which gains insight into the optical response of particle. Our analyses pave the way towards realizing tunable and polarization dependent components in UV, optical and IR frequencies for sensing and nanocircuitry applications.