American Chemical Society, Journal of Physical Chemistry B (Soft Condensed Matter and Biophysical Chemistry), 7(119), p. 3242-3249, 2015
DOI: 10.1021/jp5113813
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We investigate how to extract information on molecular bonds' orientational order in biological samples from polarized coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) microscopy. Experimentally, the mean orientation of the molecular angular distribution, as well as its second and fourth orders of symmetry, are estimated by monitoring intensity signals under a varying incident polarization. We provide a generic method of analysis of polarized signals in both CARS and SRS contrasts, and apply it to lipid bonds' orientational order imaging in multilamellar vesicles. A comparison of the two contrasts in the lipid region around 3000 $cm^{-1}$ shows that while SRS allows retrieving pure molecular order information, CARS is generally tainted by a bias from the non resonant contribution.