In CARS imaging, the pump and Stokes beams are tightly focused into the sample and a CARS image is generated by scanning either the sample or the laser beams. Besides possessing the same 3D sectioning capability afforded to 2PF and 3PF microscopy, CARS microscopy also permits non-destructive molecular imaging without any labeling. Please see CARS and SRS Raman Microscopy for additional information.
Figure 1. Energy level diagram for the CARS imaging mechanism.