Surface plasmon polariton beam focusing with parabolic nanoparticle chains

We report on the focusing of surface plasmon polariton (SPP) beams with parabolic chains of gold nanoparticles fabricated on thin gold films. SPP focusing with different parabolic chains is investigated in the wavelength range of 700-860 nm, both experimentally and theoretically. Mapping of SPP fields is accomplished by making use of leakage radiation microscopy, demonstrating robust and efficient SPP focusing into submicron spots. Numerical simulations based on the Green's tensor formalism show very good agreement with the experimental results, suggesting the usage of elliptical corrections for parabolic structures to improve their focusing of slightly divergent SPP beams.