A polarizer is nothing but an optical filter that lets the specific polarization light waves pass through. The most common types of polarizers are circular polarizers and linear polarizers – used in multiple optical instruments and techniques, and polarizing filters can find useful applications in LCD and photography technology.
Polarizers can even be designed, keeping in mind different types of electromagnetic waves besides light, including microwaves, radio waves, and X-rays. LCD reflective film is one of the most common applications of polarized technology.
Linear polarizers are categorized as absorptive polarizers, which absorb unwanted polarization in the device, and beam-splitting polarizers, that allow the unpolarized beam to split into two beams from opposite polarization states. Polarizers maintain the common axes of polarization with diverse angles of incidence called Cartesian polarizers, independent from the basic orientation of the polarizer surface.
Specific crystals show dichroism allowing preferential absorption of light, polarized in specific directions. Thus, they can also be used as linear polarizers. A Polaroid sheet with a polarizing filter operates similarly on any atomic scale to the wire-grid polarizer.
The practicality and durability of Polaroid make it a highly common type of polarizer, including photographic filters, sunglasses, and high-definition liquid crystal displays.
The beam-splitting polarizers simply split the incident beam equally into two different beams having linear polarization. Unlike absorptive polarizers, the beam splitting polarizers don’t dissipate and absorb the energy of any rejected polarization state, more suitable for the usage of high-intensity laser light beams. A true polarizing beamsplitter is also useful where two polarization components are used or analyzed simultaneously.
Polarization using Fresnel reflection
When a light beam reflects at an angle from an interface between a couple of transparent materials, the reflectivity can be diverse for light polarized in the plane of light and incidence polarized perpendicular to it.
The wire-grid polarizers convert the unpolarized beams into one having a single linear polarization. The diagonally polarized light waves also contribute to the overall transmitted polarization.
Linear polarizers successfully exploit the birefringent characteristics of crystals such as calcite and quartz. In such crystals, any beam of unpolarized light incident falling on their surface is smartly split by refraction into two rays.
The thin-film linear polarizers are glass substrates with the special optical coating applied. Either interference effects or Brewster’s angle reflections in the film cause them to act as beam-splitting polarizers smoothly. Thin-film polarizers generally don’t perform as sufficiently well as Glan-type polarizers, but they are less expensive and allow two beams that are equally well polarized.
Reflective polarizer film used in daily products like sunglasses, cameras, or TV screens cover the eyes and reduces the amount/intensity of light passing through the retina. This maintains the permitted amount of light to pass, not letting the shape of the eye change in response to extreme glare exposure. It also protects eyes from fatigue, eye power, redness, and emotional irritation caused by extreme strain. Polarized lenses neutralize the extensive sunrays, allowing the eyes to feel comfortable.