Unpolarized (natural) light
The most common polarizers used today are
(1) dichroic devices, which operate by effectively absorbing one plane of polarization
(e.g., Polaroid type-H
sheets based on stretched polyvinyl alcohol impregnated with iodine) and (2) double
refracting calcite (CaCO3) crystal
polarizers - which differentially disperse the two planes of polarization (examples of this class of
polarizers are Nicol polarizers, Wollaston prisms and Glan-type polarizers such as the Glan-Foucault, Glan-Thompson and Glan-Taylor polarizers)