Independent trapping, manipulation and characterization using fiber based CARS microspectroscopy.

This paper demonstrates a simple CARS micro-spectrometer based on a single femtosecond Ti:sapphire laser and microstructured optical fibers for frequency compression and frequency conversion. The latest version of our microspectrometer employs a three-pulse geometry, where a pump and a Stokes pulse generates a Raman polarization in the medium which is subsequently probed by a delay pulse. This three-pulse-geometry facilitates suppression of the inherent nonresonant background in the sample and makes simple chemical analysis possible through identification of the well known Raman bands of the sample under investigation. This simple microspectrometer was used to investigate a line of liver cells that were feed with mono-cultures of cis- or trans fatty acids. The two acids, oleic acid and elaidic acid, differ only in their cis-trans geometry at a single C=C double bond. From the differences in their Raman spectra, we are able to distinguish the two in the CARS-micro-spectrometer and use the imaging capabilities of the CARS-microscope to identify their incorporation in the liver cells feed with pure cis- and trans fatty cells.