This research numerically calculated the optical absorption of gold nanoparticles (AuNP) in the presence of metallic (Au) and dielectric (Si) AFM probes, illuminated by a surface plasmon polaritons on an infinite gold substrate. Nanoscale probes localize and enhance the field between the apex of the tip and the particle. However, the absorption of the nanoparticle is not always enhanced; in fact, under a gold tip, the absorption is suppressed for a 50 nm diameter AuNP. After fitting the numerical absorption data with the equation of a driven damped harmonic oscillator (HO), it was found that the AFM tip modifies both the driving force (F₀), consisting of the free carrier charge (q) and the driving field (E), and the overall damping of the oscillator (β). The enhancement or suppression of absorption with different tips can be understood in terms of competition between β and F₀. Introducing the metallic tip increases β and decreases F₀, resulting in reduced absorption. Introducing the dielectric tip, although it increases β, it also increases F₀, resulting in overall absorption enhancement. Therefore, one most consider both β and F₀ to control the absorption of nanoparticles under Surface Plasmon Polaritons.

Date Published: 14 March 2013
PDF: 8 pages
Proc. SPIE 8619, Physics and Simulation of Optoelectronic Devices XXI, 86191F (14 March 2013); doi: 10.1117/12.2002619

Published in SPIE Proceedings Vol. 8619:
Physics and Simulation of Optoelectronic Devices XXI
Bernd Witzigmann; Marek Osinski; Fritz Henneberger; Yasuhiko Arakawa, Editor(s)