Near-Field Optical Detection of Plasmon Resonance from Gold Nanoparticles: Theoretical and Experimental Evidence

The study of plasmon-induced electromagnetic fields is a very interesting topic for basic research and photonic applications. The plasmon properties depend on many factors, such as composition, size, shape and arrangement of nanoparticles. In this paper, we propose an experimental and theoretical study on the optical properties of gold nanoparticles deposited by pulsed laser ablation and investigated by near-field optical microscopy (SNOM) in a transmission far-field collection scheme. The electromagnetic field properties have been simulated by an exact theoretical analysis based on the multipolar expansion of the fields and on T-matrix approach. The theoretical model almost accurately reproduces the experimental data and makes us confident that the used method is suitable to describe more complex system of metal nanoparticles.