Optical polarizers are optical devices that can transform unpolarized or natural light into polarized light, usually by the selective transmission of polarized rays. They are used in infrared (IR), visible light, and ultraviolet (UV) applications.

Rapid Learning: Polarizing of Light. Video Credit: Rapid Learning Center / CC BY-SA 4.0

Types of Optical Polarizers

There are many different types of optical polarizers.

• Calcite polarizers are crystals that separate unpolarized light into two separate plane polarized beams.
• Circular polarizers block all photons rotating in one direction, while allowing those rotating in the opposite direction to pass. These optical polarizers are assemblies that consist of a linear polarizer and a wave retarder, usually a quarter or a half waveplate.
• Depolarizers obliterate the polarization of a polarized beam by reflecting the beam in all directions at right angles to its axis.
• Linear polarizers transmit light waves along one axis and absorb them along the other. The transmitting and absorbing axes of linear polarization are oriented at 90 degrees to each other.
• Waveplates, which are sometimes known as retardation plates, are optical elements with two principal axes (one slow and one fast) that resolve an incident polarized beam into two mutually perpendicular polarized beams. The emerging beam recombines to form a particular single polarized beam.
• Polarization rotators maneuver linearly-polarized light about an optical axis.

Optical Polarizer Review. Video Credit: edmundoptics / CC BY-SA 4.0

Specifications

For each type of optical polarizer, performance specifications include clear aperture, extinction ratio, transmittance, beam deviation, and operating temperature. Polarizer surface criteria is another important specification to consider.

More information on these specifications can be found on IEEE GlobalSpec's How to Select Linear Polarizers.

Features

Optical polarizers are available with features that include an antireflective coating, pigtail, and broadband connections. An antireflective coating will improve transmission, reduce glare, and improve readability. Broadband has a uniform optical characteristics over a wide area of the spectrum in the polarization rotator. Pigtail describes a polarization rotator which has a short length of optical fiber permanently fixed to a component. They are used to achieve accurate mounting for precision alignment of optical components.

Fiber optic pigtail. Image Credit: DIY Trade