Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 43: Poster Session II - MA 141/144 (Surface Spectroscopy on Kondo Systems; Frontiers of Surface Sensitive Electron Microscopy; Methods: Scanning Probe Techniques+Electronic Structure Theory+Other; Time-Resolved Spectroscopy of Surface Dynamics with EUV and XUV Radiation; joined by SYNF posters)

O 43.18: Poster

Tuesday, February 26, 2008, 18:30–19:30, Poster F

Interferometric detection methods for scanning near-field optical microscopy — •Christoph Zeh, Susanne C. Schneider, and Lukas M. Eng — Institute of Applied Photophysics, TU Dresden, D-01062 Dresden

Scanning near-field optical microscopy (SNOM) is a scanning probe technique which allows optical examination of nanostructures with a resolution ways below the classical diffraction limit. Hence, it finds many applications in nano science. Basically, there are two types of SNOM: the aperture-type, utilizing a tapered optical fibre for local illumination and/or detection, and the (apertureless) scattering type, in which light is scattered from a small particle, e.g. an AFM tip. Both types suffer from weak signal strengths, due to coupling losses at the fibre tip, or due to the small scattering cross sections. In order to amplify the optical near field signal, detection systems based on heterodyne or homodyne interferometry are very appropriate. Furthermore, the heterodyne detection method allows us to separate the near field's optical amplitude and phase, since the near-field signal is compared with a well known, but frequency shifted, reference signal. In this work we compare interferometric detection schemes with respect to their resolution limit and signal-to-noise ratio, for both free-beam version as well as fibre-based version.