Partial polarization of the Raman radiation combined with variations in the transmittance of the mono-chromator for radiation having different directions of polarization will lead to errors in the recorded intensity. The magnitude of these errors may vary with the age of the Raman source and with changes in the geometrical relations between the sample and the source. A properly oriented mica quarter-wave plate will reduce these errors to a negligible value in a Cary model 81 Raman spectrophotometer.
D. D. TUNNICLIFF and A. C. JONES, "Compensator for the Polarization Sensitivity of a Cary Model 81 Raman Spectrophotometer," J. Opt. Soc. Am. 51, 1430-1432 (1961)