Regensburg 2016 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 42: Plasmonics and Nanooptics III: Infrared Microscopy
O 42.3: Vortrag
Dienstag, 8. März 2016, 14:30–14:45, H4
Amplitude-modulated scattering cross-section in near-field infrared microscopy (s-SNIM) — •Frederik Kuschewski1, S.C. Kehr1, N. Awari2, B. Green2, S. Kovalev2, M. Gensch2, and L.M. Eng1 — 1Institut für Angewandte Photophysik, TU Dresden, 01062 Dresden, Germany — 2Helmholtz-Zentrum Dresden-Rossendorf, Institut für Strahlenphysik, 01314 Dresden, Germany
Scattering-type scanning near-field optical microscopy (s-SNIM) was applied to investigate the local infrared-optical properties of Ge, Si and SiGe thin films in a pump-probe experiment below the diffraction limit. The combination of s-SNIM with pump-probe techniques allows for studying electron-excitation processes at an ultimate temporal resolution, and for investigating their decay behavior.
Pump excitation is exhibited in our setup with different NIR laser systems, while near-field probing was carried out either by using a cw CO2 or the tuneable free-electron-laser at the Helmholtz-Zentrum Dresden-Rossendorf. The periodic optical excitation of the sample induces sidebands to the higher-harmonics in our s-SNIM setup, that contain the pure pump-induced information [1]. Using a special demodulation technique, the existence of these new frequencies was proven up to the 10th sideband. The investigated samples show a time-variable pump-effect in the near-field when being probed at ∼10 µm wavelength. Image scans clearly proof the resolution far beyond the diffraction limit. Our experiment proves that ultra-fast phenomena may elegantly be probed in the near field with a superb sub-diffraction resolution.
F. Kuschewski. et al., Scientific Reports 5, 12582 (2015).