Hannover 2013 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 14: Poster 1: Cluster, Femtosecond Spectroscopy

MO 14.22: Poster

Dienstag, 19. März 2013, 16:00–18:30, Empore Lichthof

Scanning Near-Field Femtosecond CARS Microscopy — •Mahesh Namboodiri, Tahir Zeb Khan, Günter Flachenecker, Sidhant Bom, and Arnulf Materny — Research Center for Functional Materials and Nanomolecular Science, Jacobs University, Campus Ring 1, D-28759 Bremen, Germany

Recently, organic semiconductors have attracted increasing attention, e.g. for the fabrication of cheap solar cells. In these devices nano-structures play an important role. The small size of these semiconductor materials results in different electronic and vibrational properties when compared to bulk samples. Also the light induced dynamics depends on size, shape and environment of the nano-structures. In order to study these processes, femtosecond time-resolved optical spectroscopy in resonance with electronic transitions is required. We have used nonlinear femtosecond time-resolved Raman techniques to obtain highly spatially resolved images in combination with near-field microscopy. We present our first results of femtosecond coherent anti-Stokes Raman scattering (fs-CARS) detected with sub-diffraction limited resolution. For this, a scanning near-field microscope with fiber tips having apertures down to 200 nm were employed. SNOM-CARS images of poly(3-hexylthiophene) (P3HT) nano-structures have been obtained. A comparison between thin films (145 nm) and thick films (1.5 µm) of this organic semiconductor shows that especially the depth resolution obtained with SNOM-CARS clearly surpasses the resolution that can be obtained with high NA (≈ 1.2) objectives.