Abstract

The optical properties of surface plasmons at the resonant wavelength depend on the geometrical nanostructure of materials, refractive indices, thickness (materials and dielectrics), and shapes of the formation unit cell nanoantennas. In this study, we take different shapes of plasmonic nanoantenna structures with a prototype of single and dual U-shapes as a common part to format a unit cell of nanoantenna by adding T and L-shapes based on a different dielectric such as, a silicon nitride, magnesium fluoride, and aluminium oxide, with gold as a variation of refractive indices. A single U-shape provides a dual spectral resonance at a wavelength range of (500-950)nm. Thus, in these proposed structures, we try to achieve a triple band with the best transmission and field enhancement distributions (electric field intensity and magnetic field intensity), and we design and simulate these fractals by using the 3D- finite difference time domain method Lumerical program with an incident source between a visible to infrared range. From the results, the triple bands have a wide range of applications in medicine as biosensors and in communication systems (optical modulators).

Keywords: Plasmonics; Multi-spectral resonances; Optical properties; Nanoantennas; Geometrical parameters; Variable refractive index