SIZE-DEPENDENT OPTICAL PROPERTIES OF COPPER NANOPARTICLE OVER A WIDE RANGE OF WAVELENGTHS: AN ELECTROMAGNETIC SIMULATION STUDY

Abstract

In this article, we modulate the optical absorption, scattering, extinction, transmission and field intensities of an ellipsoid copper nanoparticle by tuning its dimension. The finite-difference time-domain (FDTD) method is employed for this electromagnetic simulation study and a comparative investigation has been carried out. In the investigation it is found that Cu nanoparticle with 20 nm size exhibiting the optical absorption at the resonant wavelength ~530 nm. This plasmon peak is shifted to ~550 nm when the particle size is increased to 40 nm. In addition to shifting, the enhancement of the plasmon peak is also observed. This nonlinear enhancement arises due to the size dependent property of the surface plasmon resonance (SPR). For smaller nanoparticle, the scattering is found to be negligible as compared to the larger particle. The scattering becomes dominant as the particle size increases beyond 28 nm. The scattering cross-sections of all the particle decreases at the longer wavelength. All the structures exhibit a strong transmission minimum at a wavelength close to 590 nm in the visible spectrum. However, above 600 nm high transmission is observed. The electric field intensity is also enhanced from 5.15 (V/m)2 to 16.9 (V/m)2 as the particle size increases from 20 nm to 40 nm. We strongly believe that this research could provide an overall idea about the importance of particle size variation while fabricating Cu based solar energy harvesting systems, plasmonics photovoltaic devices etc.