Raman Scattering for Label-Free Chemical Imaging

Raman spectroscopy provides chemical information by detecting light scattered from a monochromatic source (such as a laser) at energies that correspond to molecular vibrations. Because Raman spectroscopy commonly uses visible lasers, the spatial resolution is approximately the same as what can be seen with an optical microscope. First demonstrated in the 1970s, coupling Raman spectroscopy with microscopes enabled the chemical information to be obtained from a focused laser spot. By moving the laser across the sample and recording the Raman spectrum at each location, images can be generated from changes in intensity at different Raman shifts that spatially characterize the molecules present. From the development of the Raman microprobe to today, advances in instrumentation have increased the speed, sensitivity, and spatial resolution of Raman microscopy. This article covers the fundamentals of Raman microscopy and how technological advances are enabling a variety of applications.