Regensburg 2013 – scientific programme
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O: Fachverband Oberflächenphysik
O 63: Plasmonics and Nanooptics V
O 63.5: Talk
Thursday, March 14, 2013, 11:30–11:45, H38
Surface Plasmons onordered and bi-continuous spongy nanoporous gold films — •Neha Sardana1, Carsten Reinhardt2, and Jörg Schilling1 — 1ZIK SiLi-nano, MLU, Halle, Germany — 2Laser Zentrum Hannover, Hannover, Germany
In sub-wavelength optics of thin metal films (negative real dielectric constants), the dispersion relation of surface plasmons (SPs) on metal/dielectric surfaces 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 resp. We investigate tuning of dispersion of SPs by keeping εd fixed but changing εm via introducing a nanoporosity into the metal. We compare a bi-continuous nanoporosity fabricated by dealloying with a uniform hexagonal porosity formed by evaporating gold Au on self-ordered nanoporous templates. The porosity leads to increase in εm which causes red shift of the SP frequency at constant kx. This is observed experimentally by applying angular resolved reflection measurements. A dip in reflectivity, which shifted to shorter wavelength with increasing angle of incidence, was identified. This shift is in good agreement with effective medium theory’s. Determination of SP propagating losses, was performed by leakage radiation microscopy in both direct and Fourier space. It is observed that ordered nanoporous gold film exhibits lesser scattering and overall lower attenuation than the spongy nanopores. This metallic structure represents a bridge between designer plasmons at structured metal surfaces for microwave range and classic SP optics with plane metal layers in visible allows larger flexibility in SP devices.