Modern Raman imaging: vibrational spectroscopy on the micrometer and nanometer scales.

Raman microscopes are currently used in various fields of research because they allow for label-free sample investigation. Moreover, the inherently low scattering cross section of Raman spectroscopy, as well as its diffraction-limited lateral resolution, has been overcome by new Raman microscopy techniques. Nonlinear methods such as coherent anti-Stokes Raman spectroscopy and stimulated Raman spectroscopy reduce measurement times and improve z resolution, allowing for three-dimensional spectroscopic imaging of biological samples. Moreover, tip-enhanced Raman spectroscopy, a near-field optical technique that combines scanning-probe microscopy with the enhancement offered by surface-enhanced Raman scattering, enables Raman spectroscopic imaging far below the optical diffraction limit. We cover the theoretical and technical aspects of Raman microscopy and related new imaging techniques and review some very recent applications in graphene research and cell biology.