Effective polarizability and optical resonances of a square lattice of rod-like metal nanoparticles on a dielectric substrate

Resonance properties of the lattice of rod-like nanoparticles are studied in the local field approximation; the characteristics of single nanoparticles are calculated within the framework of the equivalent spheroid approach. According to the results of the calculations, a blue shift of the maxima of the imaginary part of the effective transverse polarizability for the square lattice of nanocylinders with a decrease in their effective aspect ratio was established. The imaginary part of the effective transverse polarization of the lattice of cylinders is four orders of magnitude greater than the corresponding value for a single cylinder. The lattice resonance frequency increases when metals with a higher plasma frequency are used or when the lattice is placed in a medium with a lower dielectric constant. The obtained results indicate a significant influence of the size, shape, and material of rod-like nanoparticles, as well as the surrounding medium, on the frequency dependence of the imaginary part of the effective transverse polarization of the lattice. The possibility of controlling the lattice resonance frequency by changing the effective aspect ratio of the nanoparticles forming the lattice has been demonstrated. The strong interaction between the constituent elements of the lattice leads to an increase by four orders of magnitude in the imaginary part of the effective transverse polarizability and the absorption cross section of the lattice in comparison with a single nanoparticle.