Direct imaging of molecular symmetry by coherent anti-Stokes Raman scattering

TL;DR

This paper introduces a novel symmetry-resolved vibrational microscopy technique using circularly polarized CARS, enabling simultaneous chemical and symmetry analysis of samples with enhanced contrast and selectivity.

Contribution

The authors demonstrate a new method to determine molecular symmetry using circularly polarized CARS in a single measurement, improving contrast and chemical specificity.

Findings

Quantified vibrational bond organization in crystalline samples

Enhanced contrast for anisotropic biological samples

Provided symmetry information not accessible by traditional Raman techniques

Abstract

Nonlinear optical methods, such as coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS), are able to perform label free imaging, with chemical bonds specificity. Here, we demonstrate that the use of circularly polarized light allows to retrieve not only the chemical nature but also the symmetry of the probed sample, in a single shot measurement. Our symmetry-resolved scheme offers simple access to the local organization of vibrational bonds and as a result provides enhanced image contrast for anisotropic samples as well as an improved chemical selectivity. We quantify the local organization of vibrational bonds on crystalline and biological samples, thus providing new information not accessible by spontaneous Raman and SRS techniques. This work stands for a novel symmetry-resolved contrast in vibrational microscopy, with potential application in biological diagnostic.