Cary model 14 spectrophotometers like other prism and grating instruments have polarization characteristics that affect the transmittance values of anisotropic or dichroic materials. In the uv, the degree of polarization is fairly constant from 3000 Å to 4000 Å, whereas in the visible, it shows some variation with wavelength. In the near ir, the variation of the degree of polarization with wavelength is large, showing sharply defined maxima at approximately 0.77 µ, 0.97 µ, and 1.27 µ. The spectral transmittance of optical quality sapphire, a uniaxial crystal, cut at 45°, 60°, and 90° to the c axis, showed undulations for certain orientations of the privileged directions.
Marian E. Hills, Allen L. Olsen, and Lawrence W. Nichols, "Polarization in Cary Model 14 Spectrophotometers and Its Effect on Transmittance Measurements of Anisotropic Materials," Appl. Opt. 7, 1437-1441 (1968)