Simulation of arrays of metal nano-particles using a monochromatic recursive convolution finite-difference time-domain method

Abstract

The arrays of metal nano-particles can support localized surface plasmon resonance (LSPR) modes, making them suitable for coloring applications. The LSPR peaks of such arrays can be tuned by changing the structural parameters, such as, shape, size, of each particle and the interparticle distance. In this paper we study the dependence of LSPR properties of arrays on the structural parameters. The extinction spectra of a spherical particle can be computed analytically using Mie theory. No analytical computation method is available for particle arrays. Numerical methods, e.g., discrete dipole approximation, finite-difference time-domain (FDTD) method are used. Here, we compute the extinction spectra of linear arrays of nano-particles using a monochromatic version of recursive convolution (RC) FDTD method. We developed this method to be able to use the handbook values of permittivity of the material of the particles at each wavelength. The simulations indicate that the position and size of the peaks of the extinction spectra are determined by the interparticle distance between any two particles and the number of particles in the array. In case of linear arrays of infinite, silver nano-cylinders, the LSPR peak can be shifted toward the longer wavelengths (red-shift) by reducing the interparticle distance. The red-shift increases as the interparticle distance becomes smaller. The peaks of extinction spectra become larger as the number of particles in the array increases.