Metal nanoparticles in strongly confined beams: transmission, reflection and absorption

We investigate the interaction of tightly focused light with the surface-plasmon-polariton resonances of metal nanospheres. In particular, we compute the scattering and absorption ratios as well as transmission and reflection coefficients. Inspired by our previous work in Ref. [1], we discuss how well a metal nanoparticle approximates a point-like dipolar radiator. We find that a 100 nm silver nanosphere is very close to such an ideal oscillator. Our results have immediate implications for single nanoparticle spectroscopy and microscopy as well as plasmonics.