Regensburg 2007 – scientific programme

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BP: Fachverband Biologische Physik

BP 20: Novel Methods

BP 20.2: Talk

Wednesday, March 28, 2007, 17:45–18:00, H43

Nonlinear vibrational microscopy with coherent anti-Stokes Raman scattering — •Christoph Heinrich, Alexander Hofer, Stefan Bernet, and Monika Ritsch-Marte — Division for Biomedical Physics, Innsbruck Medical University, Müllerstraße 44 A-6020 Innsbruck, Austria

It is well known that the intrinsic ability of molecules to rotate and vibrate can be utilized to obtain spectroscopic resolution. Commonly used methods like Raman and infrared spectroscopy have, however, crucial shortcomings in microscopy. Infrared microscopy yields a lack of resolution due to the long excitation wavelengths whereas Raman microscopy does only deliver a weak signal. Coherent anti-Stokes Raman scattering (CARS) microscopy has emerged as new microscopic method a few years ago combining both, high resolution and an intense signal. High resolution is guaranteed through the blue shifted anti-Stokes signal making it also easy to separate it form the excitation laser beams and fluorescence by means of a short pass filter. The coherent signal is enhanced compared to the linear Raman effect due to stimulated emission and constructive interference in the direction determined by the phase matching condition. A drawback unfortunately is a frequency independent nonresonant background always accompanying the resonant signal. Wide-field CARS microscopy presented in this contribution is a non-scanning approach that allows high speed imaging. Latest results and prospects will be discussed.