Polarization scrambling by high pressure cell windows as a function of pressure up to 2 kbar has been measured for two window materials and two sizes of plug apertures. Measured scrambling was about 1% for quartz, 0.5% for float glass, and decreased with decreasing aperture size. The amount of scrambling decreased significantly with time when the cell was left pressurized. A qualitative explanation of the results, based on changes in the P44 Pockels coefficient with pressure is given.
D. M. Cantor, J. Schroeder, and J. Jonas, "Polarization Scrambling by Optical Windows Used for Light Scattering Experiments at High Pressures," Appl. Spectrosc. 29, 393-396 (1975)