General Raman Spectroscopy Overview

Raman spectroscopy directly probes the vibrational and rotational states of a molecule via scattering from a molecule of merely one photon in a million. Unlike infrared spectroscopy, no sample preparation is required, nor is there interference due to water content in the sample. Samples can be analyzed against a library in the field using non-destructive,…

Surface-enhanced Raman Scattering

Raman signals are inherently weak, especially when using visible light excitation and so a low number of scattered photons are available for detection. One method to amplify weak Raman signals is to employ surface-enhanced Raman scattering (SERS). SERS uses nanoscale roughened metal surfaces typically made of gold (Au) or silver (Ag). Laser excitation of these…

Coherent anti-Stokes Raman Scattering

Coherent anti-Stokes Raman scattering (CARS) is a nonlinear four-wave mixing process that is used to enhance the weak (spontaneous) Raman signal. In the CARS process a pump laser beam (at frequency ωpump) and a Stokes laser beam (at ωStokes) interact, producing an anti-Stokes signal at frequency ωCARS = 2ωpump – ωStokes. The Stokes beam (ωStokes)…