Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 77: Poster: Plasmonics and Nanooptics

O 77.16: Poster

Mittwoch, 14. März 2018, 18:15–20:30, Poster A

Scanning near-field optical spectroscopy with an inline interferometer for probing local absorption — •Jens Brauer, Jinxin Zhan, Petra Groß, Manuela Schiek, and Christoph Lienau — Carl von Ossietzky Universität Oldenburg

Combining spectroscopy methods with nanoscale probing techniques such as scanning near-field optical microscopy (SNOM) helps to measure vibrational fingerprints, quantifiy chemical composition or study the interaction of light with plasmonic nanoparticles or hybrid nano structures. Until now local spectra on the nanoscale are mainly measured indirectly, for example by repeated SNOM scans using monochromatic light and tuning the wavelength of the laser or by Fourier transform interferometry techniques. Nanoscale spectroscopy with SNOM is thus limited either in spectral resolution or in scan speed. A direct spectrometer approach is usually thought not to be possible since high-frequency modulation techniques are needed for background suppression.

We demonstrate a way to suppress background fields over a broad spectral range employing an inherently stable in-line interferometer in a homodyne detection scheme. In combination with a fast line camera it allows to directly acquire spectra employing existing modulation techniques. We record near-field spectra with a spatial resolution of 20 nm and reveal a spectral variation below the resolution limit of widefield microscopy. With a microscopic model of the sample we relate this spectral variation to a local change of the morphology.