Polarization measurements in Raman microspectroscopy. I—Isotropic samples

A quantitative analysis is made of the problem of obtaining accurate polarization measurements in Raman microspectroscopy. The introduction of experimentally determined correction factors arising from the optical properties of the beam splitter allows the depolarization by the microscope objective to be studied separately. Correction curves are calculated for the various parameters which characterize the light‐excitation path and the light‐collection path. These parameters are functions of both the numerical aperture of the objective and the refractive index of the (isotropic) sample. The introduction of these parameters into the expressions for the depolarization ratios of various Raman and resonance Raman bands accounts well for the differences noted between the results of the present microprobe measurements and those obtained with conventional instruments. The values determined here are, within experimental error, in agreement with the calculated results over a large range of depolarization ratios.