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Q: Quantenoptik und Photonik
Q 54: Anwendung ultrakurzer Lichtimpulse II
Q 54.3: Talk
Tuesday, March 8, 2005, 18:00–18:15, HU 1070
Gated heterodyne coherent anti-Stokes Raman scattering for chemical imaging — •Marco Greve1, Bernd Bodermann1, Harald R. Telle1, Peter Baum2, and Eberhard Riedle2 — 1Physikalisch-Technische Bundesanstalt, Braunschweig — 2LS für Biomolekulare Optik, Ludwig-Maximilians-Universität München
The use of molecular vibrations as contrast mechanism makes coherent anti-Stokes Raman scattering (CARS) microscopy a powerful method for molecule-specific imaging [1]. As coherent four-wave mixing process CARS provides a fixed phase relationship between the four light fields and allows the heterodyne detection of the CARS signal if a tunable phase-coherent local oscillator pulse is available. With proper pulse timing such a detection scheme - gated heterodyne CARS - is capable of significantly improving the signal-to-background ratio, i.e. the image contrast.
We demonstrate this novel method with three femtosecond noncollinear optical parametric amplifiers (NOPAs) seeded by a common white-light. Two NOPAs have previously been shown to emit phase coherent light [2]. A contrast improvement of more than two orders of magnitude compared to conventional CARS was achieved with deuterated benzene as sample and heavy water as a possible solvent.
Further applications include the thermometry of combustion processes.
[1] M. D. Duncan et al., Opt. Lett. 7, 350 (1982)
[2] P. Baum et al. , Opt. Lett. 28, 185 (2003)