Polarization measurements in raman microspectroscopy.

A number of quantitative polarization measurements have been made by Raman microspectroscopy. After correction for effect of the beam splitter used in Raman microprobe instruments, the depolarization introduced by the large aperture objectives is evaluated theoretically with the use of the characteristics of the objectives and the isotropic refractive index of the sample. In the case of cubic crystals the theoretical expressions account for the observed depolarizations, which are found to be weak. For uniaxial and biaxial crystals the birefringence introduces an additional depolarization. This depolarization can be reduced to a negligible value with the use of an objective of moderate aperture, if the effective volume of the sample is near the surface, and if the orientation of the surface with respect to both the refractive index directions and the microscope axis is correct