Theoretical studies of the optical properties of plasmon resonance on silver nanoparticles in the near-field optics

Near-field spectral characteristics, images, and optical parameters of silver nanoparticles are studied using Green's tensor. The Lippmann-Schwinger integral equation is discretized, and numerically solved with complex-conjugate gradient method-fast Fourier transform algorithm. Simulation models include placing nanoparticles in either an infinitely homogeneous medium or on a substrate, and illuminated either directly with plane waves or through a glass substrate under total internal reflection. Simulation results suggest that local plasmon resonance redshifts to longer wavelengths when dielectric constant of the surrounding medium increases or when a substrate is presented, but blueshifts to shorter wavelengths when the height of a nanoparticle increases. Due to the exponential attenuation behavior of evanescent waves, total intensity of electrical field attenuates quickly as the detection distance increases. Optical efficiencies, scattering efficiencies, absorption, and extinction efficiencies of Ag nanoparticles are also reported.