Regensburg 2007 – scientific programme

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O: Fachverband Oberflächenphysik

O 17: Poster Session I (Nanostructures at Surfaces; Metal Substrates: Epitaxy and Growth; Methods: Scanning Probe Techniques; Phase Transitions)

O 17.49: Poster

Monday, March 26, 2007, 17:30–20:30, Poster C

Phase-controlled Homodyne Interferometric Detection for s-SNOM — •Marcus Cebula, Susanne Schneider, and Lukas Eng — Institute of Applied Photophysics, TU Dresden, D-01062 Dresden

Apertureless or scattering-type scanning near-field optical microscopy (s-SNOM) is a versatile technique for high-resolution optical investigations of various materials. Common systems contain homodyne or heterodyne interferometric detection with lock-in demodulation to analyse the optical near-field signal. These methods are restricted in there application especially concerning their wavelengths range.

To eliminate these restrictions, a phase-controlled homodyne interferometric setup was designed. This setup can be used in the entire near-UV to far-IR spectral range. It consists of an enhanced homodyne interferometer containing a phase-modulated reference beam. By using additional lock-in demodulation and controlling techniques, a wavelength independent phase-regulation and therewith the possibility to measure both the optical amplitude and phase of the near-field signal, becomes available. The two signals can be measured simultaneously and also up to higher harmonic modes.

Our setup is designed to allow interferometric near-field measurements by the use of a free-electron laser, available at the Forschungszentrum Rossendorf. This precisely tunable light source covers the wavelength regime from 4 to 100 micrometer, and was used up to now for near-field optical investigations of organic thin films and ferroelectric single crystals by means of a direct intensity analysis.