Specialty Optical Polarizers

Specialty optical polarizers use the optical properties of a medium to alter the polarization of light. Typical mediums for specialty optical polarizers include birefringent materials such as calcite, as well as photonic crystals and liquid crystals. Birefringent materials have an anisotropic crystal structure such that different polarization orientations experience difference indices of refraction. Photonic crystals in specialty optical polarizers use periodic optical structures combined with carefully-placed defects to produce specific polarization effects. The liquid crystals used in specialty optical polarizers are rod-like molecules that are arranged in certain patterns to determine the type of polarization output. The rods in these liquid crystals are directed by electric fields, and the rods move to align with the field. There are three main types of specialty optical polarizers that use liquid crystals: radial polarizers, azimuthal polarizers, and elliptical polarizers. Radial polarizers and azmiuthal polarizers are two main types of specialty optical polarizers. Radial specialty optical polarizers convert a linearly-polarized light into a beam that is still linearly polarized, but is divergent from a single radial point. Radial polarization results when specialty optical polarizers have rods in liquid crystals set into a specific radial pattern. Radially-polarized light is completed for light that is perpendicular to the cell axis. Azmiuthal specialty optical polarizers take linearly-polarized light and modify it into a beam that remains linearly polarized, but that curls around a single point. This curling occurs because the rods in the liquid crystals are arranged in an azimuthal or counter-clockwise circular pattern. Typically, azimuthally-polarized light is executed for light that is parallel to the cell axis. Elliptical polarizers are another basic type of specialty optical polarizers. Elliptical polarization describes states where the ordinary and extraordinary plane waves are out of phase by more than 0 degrees, but less than 90 degrees. Elliptical polarizers achieve the desired phase difference by cutting a birefringent material to a specific length. Specialty optical polarizers that produce a phase difference of 90 degrees are called waveplates, and are said to produce circularly-polarized light. Specialty optical polarizers that produce no phase-change are said to produce linear polarized light.

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