Polarizing Films

High-quality mineral polarizers such as tourmaline and calcite-based Nicol prisms have been superseded by other methods of producing polarized light, most notably through the use of polarizing polymer films. Today, while both iodine and iodine-free polarized films are widely available, it is still the case that those incorporating iodine are regarded as being superior in terms of transmittance and polarization efficiency for the visible part of the electromagnetic spectrum. Iodine has played an outstanding role in the production of polarized light. The origin of the commercial polarizing film is found in Herapath's 1852 paper in Philosophical Magazine. Iodine is no longer critical to the preparation of polarizers, of which there are now innumerable types depending on the wavelengths of interest and the applications. The phenomena of diffraction, interference, scattering, and nonnormal reflection and transmission have all been exploited to fashion practical light polarizers.