Coherent Anti-Stokes Raman Scattering Microscopy for High Speed Non-Staining Biomolecular Imaging

Vibrational microscopy (Raman microscopy and infrared microscopy), which observes molecular vibrations, gives us the information of molecular species without staining because the observed signals are originated from intrinsic molecules of a cell. However, infrared radiation is absorbed with water, and the long wavelength (3-10 mu m) limits the spatial resolution to several micrometers. Spontaneous emission of Raman scattering is quite feeble, and the Raman scattering often overlaps with one-photon fluorescence from a specimen. Coherent anti-Stokes Raman scattering (CARS) microscopy, which is one of the nonlinear Raman microscopy, is a method to overcome those problems. In this review, present system of CARS microscopy, the methods of background rejection, and applications are introduced.