Dresden 2011 – scientific programme

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MO: Fachverband Molekülphysik

MO 15: Linear and nonlinear Raman Spectroscopy

MO 15.6: Talk

Wednesday, March 16, 2011, 16:00–16:15, MER 02

Shaper Assisted Multiplex CARS — •Jean Rehbinder, Christoph Pohling, Tiago Buckup, and Marcus Motzkus — Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany

Coherent Anti-Stokes Raman Scattering (CARS) is one of the most specific non-linear effects, able to produce microscopical chemical maps without any label. Compared to its spontaneous counterpart, the coherent nature of CARS gives rise to stronger signals and hence an increase of the speed of acquisition. A limiting factor for this speed then becomes the CCD detector used to acquire whole spectra. Video-rate capabilities of CARS have been demonstrated when probing a single Raman level, sacrificing, however, chemical specificity for speed. Here we present a new scheme suited for single-channel as well as for spectrally-resolved applications [1]. In this approach, we exploit the fact that the excitation probability for Raman modes is directly proportional to the spectral intensity of the broadband Stokes pulse in a Multiplex CARS setup. By use of an amplitude shaper we gain full control of the excited levels across the whole spectral range, where modes from 400 cm⁻¹ to 3100 cm⁻¹ can be selected with a resolution of 7 cm⁻¹. The method is illustrated by imaging a polymer blend containing polystyrene, polyethylene and polymethylmethacrylate with close, partly overlapping bands selected only by the shaper. [1] Rehbinder,J. et al., Optics Letters 35 (2010) 3721.