Berlin 2018 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 4: Plasmonics and nanooptics: Fabrication and characterization
O 4.4: Vortrag
Montag, 12. März 2018, 11:15–11:30, MA 041
An experimental near-field study of subwavelength nanoaperture arrays in freestanding gold films — •Mike Prämassing1, Stephan Irsen2, and Stefan Linden1 — 1Physikalisches Institut, Universität Bonn, D-53115 — 2Research Center caesar, D-53175
Periodic nanoaperture arrays in metallic films with a thickness of several tens of nanometers are well known to exhibit extraordinary optical transmission orders of magnitude higher than predicted by standard aperture theory [1]. In contrast, for very thin metal films a suppressed optical transmission has been reported [2]. Both effects can be explained by resonant coupling of the incident light to surface plasmon polaritons (SPPs) via the array. Here, we present a new fabrication approach for nanoaperture hole arrays in freestanding gold films with thicknesses ranging from 20 nm to 80 nm. Optical transmission spectra of our samples reveal extraordinary transmission, as well as suppressed transmission for the thinner films. Furthermore, we utilize electron energy-loss spectroscopy (EELS) and scattering-type scanning near-field optical microscopy (s-SNOM) as two complementary near-field imaging techniques. EELS directly yields full spectroscopic data of the out-of-plane electric field amplitude |Ez|. Combining an interferometric transmission s-SNOM setup with a tunable near-infrared laser source allows for amplitude- and phase-resolved spectroscopic data of Ez. In summary, we are able to connect the SPP near-field patterns to the features in the far-field spectra.
[1] Ebbesen et al., Nature 391, 667-669 (1998).
[2] Braun et al., Phys. Rev. Lett. 103, 203901 (2009).