Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 97: Nanostructure at Surfaces: Structures and Properties

O 97.9: Vortrag

Freitag, 20. März 2015, 12:30–12:45, MA 005

Background suppression in near-field optical microscopy by generalized lockin detection — •Susanne Hartmann¹, Falk Müller¹, Yi Huang², Abeer Al Mohtar², Aurélien Bruyant², Michael Ludemann¹, and Anne-D. Müller¹ — ¹Anfatec Instruments AG, Melanchthonstr. 28, 08606 Oelsnitz, V. — ²Laboratoire de Nanotechnologie et Instrumentation Optique, CNRS (FRE 2671), Universite de Technologie de Troyes, 10010 TROYES cedex, France

A detection scheme is presented that allows to simultaneously measure signal amplitude and phase in near-field optical microscopy (SNOM) with the aid of interferometry. The method is based on a phase modulation of the reference arm inside the interferometer followed by a demodulation of the measured signal with specifically chosen trigonometric functions. The output can be understood as generalized lockin technique (GLIA). The GLIA successfully extracts the signal while suppressing the background. In case of an additional tip oscillation at f_r, a further background subtraction is achieved by a preceding amplitude demodulation of the GLIA’s input signal at f_r. The calculations are verified by measurements on gold discs. The method is a crucial step for background suppression with applications not only in near-field optical microscopy.