Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 74: Plasmonics and nanooptics IV
O 74.9: Vortrag
Donnerstag, 29. März 2012, 18:00–18:15, MA 005
Dispersion control of propagating surface plasmons on nanoporous gold — •Neha Sardana1,2 and Jörg Schilling1 — 1Centre for Innovation Competence SiLi-nano, Martin Luther University of Halle-Wittenberg, Karl-Freiherr-von-Fritsch-Str. 3, 06120 Halle (Saale), Germany — 2International Max Planck Research School for Science and Technology of Nanostructures, Weinberg 2, 06120 Halle (Saale), Germany
Surface Plasmons (SPs) have wavelengths shorter than light and allow its strong confinement hence forming the backbone of current sub-wavelength optics. Their dispersion relation on plane metal/dielectric surfaces follows directly from Maxwell equations and is given as kx=(ω/c)*√[εm*εd/ (εm+εd)], where kx describes the wave vector of the SP and εm and εd are the dielectric constants of the metal and dielectric respectively. To control the dispersion of the SPs, normally εd is varied. An increase in εd causes a red shift of the SP at constant kx or an increase of kx for constant SP frequency ω. However in our experiments we explore the same possibility by changing the value of εm by introducing nanoporosity by dealloying method into the metal. Reflection measurements in the Kretchmann configuration are used to determine the dispersion relation of the SP on nanoporous gold/air interface. A characteristic dip in reflectivity, which shifted to shorter wavelength with increasing angle of incidence, was identified. This shift is compared with the Bruggeman effective medium theory. The experimental analysis proves that SP dispersion relation can be controlled by porosity of metal leading to larger flexibility in SP devices.