Regensburg 2016 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 23: Plasmonics and Nanooptics: Light-Matter Interaction, Spectroscopy

O 23.2: Poster

Montag, 7. März 2016, 18:15–20:30, Poster E

Excitation of Surface Phonon Polaritons using an Infrared Free-Electron Laser — •Nikolai Passler, Ilya Razdolski, Martin Wolf, and Alexander Paarmann — Fritz-Haber-Institut der Max-Planck-Gesellschaft

Similar to surface plasmon polaritons (SPPs) at metal surfaces, polar dielectrics can support surface polaritons. These surface phonon polaritons (SPhPs) [1] emerge due to negative permittivity between transverse and longitudinal optical phonon frequencies, the so-called Reststrahl region. As for SPPs, these excitations are non-radiative due to a wave vector mismatch, which is why they can only be excited in sub-wavelength nanostructures or via prism coupling. SPhPs have, however, much longer lifetimes than SPPs, promising low-loss optical modes below the diffraction limit.

Here, we employ the Otto geometry [2] for prism coupling to excite SPhPs at the SiC-air interface, using a tunable mid-infrared Free-Electron Laser (FEL). In this configuration, the necessary momentum for SPhP excitation is provided by the evanescent wave leaking into the air gap between prism and sample for incident angles of total internal reflection inside the prism. The optimal coupling conditions for the phase-matched SPhP excitation are studied using reflectance spectroscopy. Additionally, the resonant nonlinear response of the excited SPhPs is probed by second harmonic generation spectroscopy.

[1] Neuner et al., Opt. Lett. 34, 2667 (2009)

[2] Otto, Zeitschrift für Physik 216, 398 (1968)