Comparison of the spectrum of a calcite crystal (polarized E^c) taken with polarizers of three different polarization efficiencies.
The apparent height of an absorption band of an anisotropic
solid can be significantly decreased is polarizers of low
polarization efficiency are used. This graph compares the
spectrum of calcite taken with a polarizer of zero
efficiency (red trace -
unpolarized), a Au-wire-grid polarizer of moderate
efficiency on a AgBr substrate; and a LiIO3
(Glan-Thompson design) polarizer of very high polarization
efficiency (back trace). For the stronger bands, the high
efficiency polarizer produces higher absorbance values which are
close to the true absorption intensity of the calcite.
From: Libowitzky E, Rossman GR (1996) Principles of quantitative absorbance measurements in anisotropic crystals. Physics and Chemistry of Minerals 23, 319-327.