There has been considerable discussion of the problems associated with the measurement of Raman scattering tensor components and depolarization ratios. Accurate measurement of these quantities requires the recorded data to be corrected for the relative efficiency of the instrument. The relative efficiency is a function of both the polarization and the wavelength of the incident radiation. While several components of the spectrometer affect the polarization character of the radiation, the dominant cause is the difference in efficiency associated with a grating when the radiation is polarized parallel or perpendicular to the grating rulings. This difference in efficiency for the two polarizations may be quite large for wavelengths larger than the blaze wavelength. For example, the ratio of the efficiencies for 657.8 wavelength radiation polarized perpendicular and parallel to the rulings for two Jarrell-Ash 1180-line/mm gratings blazed at 500 nm and mounted in a Spex model 1401 double monochromator is 3.4 to 1.0.
Larry A. Rahn, Paul A. Temple, and C. E. Hathaway, "On "Scrambler Plates" Used to Depolarize Visible Radiation," Appl. Spectrosc. 25, 675-677 (1971)