Polarizer

A polarizer (also spelled polariser) is an optical filter whose transmission depends strongly on the polarization state of the light that reaches it. A linear polarizer passes light polarized in one direction and either absorbs the orthogonal polarization or sends it in a different direction; a circular polarizer passes one handedness of circular polarization. Common types include stretched-polymer sheet polarizers, reflective polarizing films, birefringent crystal prisms, thin-film coatings and wire grids.

Polarizers are found throughout virtual reality (VR) and augmented reality (AR) hardware. Every LCD panel needs polarized light, and in a VR headset the absorption in its polarizers and color filters is part of the reason only about 2% of the backlight gets through the panel. The pancake lenses used in many current headsets fold the light path with a reflective polarizer, a quarter-wave plate and a half mirror, and AR light engines built on liquid crystal on silicon (LCoS) panels use polarizing beam splitters to separate the illumination from the image light. Polarizing glasses are also used to give each eye its own image on 3D displays.

Reviewed 13 October 2026. Polarizer principles, types and specifications against RP Photonics; polarizer history against FSU, MacTutor, HBS, Optica and Land patent; VR/AR display and pancake-lens claims against the Yin 2022, Xiong 2021, 3M 2017 papers, UploadVR, 3M and Samsung sources; research paper details via Crossref and abstracts About review dates.

How polarizers work

For linearly polarized light whose polarization direction makes an angle θ with a polarizer's pass direction, the transmissivity follows a cos²θ dependence. This relation is Malus's law; it can be understood by splitting the incoming polarization into a component along the pass direction and a component along the blocked direction. Two polarizers with crossed pass directions therefore transmit no light in the ideal case. A polarizer cannot convert light of an arbitrary polarization into the desired state; it can only remove the unwanted part.

Most polarizers act on linear polarization. A circular polarizer is usually built by combining a linear polarizer with a quarter-wave plate, the same kind of birefringent retarder discussed in the article on birefringence.

An ideal polarizer would pass all of the light in the wanted state, block all of the orthogonal state, and do so at every wavelength, over a wide range of incidence angles and at any power level, without distorting the wavefront. Real polarizers fall short on each of these points. The specifications used to compare them include:

• Polarization extinction ratio (also called contrast ratio): the ratio of maximum to minimum transmissivity. RP Photonics gives about 500:1 as an example for a simple sheet polarizer and up to 10⁶:1 for a high-quality birefringent polarizer such as a Glan-Taylor prism. The ratio can differ between the two outputs of a polarizing beam splitter cube.
• Throughput or insertion loss for the wanted polarization, often limited by the anti-reflection coatings.
• Wavelength range and acceptance angle. Some polarizing cubes accept only about 3 degrees, while dichroic glass and wire-grid polarizers can work over ranges of the order of 10 degrees or more.
• Wavefront distortion, power handling and damage threshold, clear aperture, and the angle at which a rejected beam leaves the device.

Types

Type	How it separates polarizations	Notes
Absorptive (dichroic) sheet polarizer	A doped polymer sheet stretched in one direction aligns its polymer chains; light polarized along the chains is strongly absorbed and the perpendicular polarization is weakly absorbed	Can be made large and cheaply; used in sunglasses and polarizing 3D glasses; low power handling (RP Photonics cites an intensity of about 1 W/cm2 as possibly critical for simple polymer sheets)
Dichroic glass polarizer	Silver or copper nanoparticles embedded in a thin glass plate	More expensive than polymer sheet and not available in very large sizes, but with a substantially better extinction ratio
Reflective polarizing film	Transmits one linear polarization and reflects most of the other instead of absorbing it	Widely used in LCD backlights to recycle the rejected light; multilayer polymer versions have been used as the reflective polarizer in pancake lenses
Birefringent crystal polarizer	Two pieces of a birefringent crystal (for example calcite, quartz, yttrium vanadate, BBO or magnesium fluoride) joined with different optical-axis orientations. In Nicol, Glan-Thompson, Glan-Taylor and Glan-Foucault prisms one polarization undergoes total internal reflection; Wollaston, Nomarski, Rochon and Sénarmont prisms rely only on different refraction angles	High power handling because the rejected light is redirected rather than absorbed; high extinction ratios; some designs accept only a narrow range of incidence angles, which is usually no problem with low-divergence laser beams
Thin-film polarizer	A dielectric multilayer coating whose reflectivity is strongly polarization-dependent at non-normal incidence; built as coated plates (often used at Brewster's angle) or as polarizing beam splitter cubes	Works over a limited wavelength range (up to a few hundred nanometers); can be made large
Wire-grid polarizer	Very narrow, sub-wavelength metal stripes made lithographically on glass (or free-standing for longer wavelengths) reflect one linear polarization and transmit the other	Can be used at very high average power levels and over a comparatively large range of incidence angles; wire-grid polarizers for visible light and wire-grid polarizing beam splitters for projectors and liquid crystal displays are sold commercially

History

Étienne-Louis Malus discovered in 1808 that light could be polarized, after looking through a rotating crystal of Iceland spar at sunlight reflected from the windows of the Luxembourg Palace in Paris. His account of polarization by reflection was published in 1809.

In 1852 William Bird Herapath found that iodine combined with a quinine salt forms light-polarizing crystals, now called herapathite, but the crystals were too small and costly to be practical. Edwin H. Land took a different route: instead of growing one large crystal, he made a film containing millions of micrometer-sized polarizing crystals aligned with one another. According to Harvard Business School's Polaroid collection, Land's 1928 breakthrough was to align microscopic crystals suspended in a lacquer with a magnetic field, and he then coated plastic sheets with the crystals and stretched them to align them before they dried; he applied for his first patent on a light-polarizing sheet in 1929. The company he formed with his Harvard physics instructor George W. Wheelwright III, Land-Wheelwright Laboratories, was renamed Polaroid Corporation in 1937. Early customers included Eastman Kodak, which contracted in 1934 for polarizing camera filters to reduce glare, and American Optical, which signed a contract in 1935 to produce sunglasses marketed as Polaroid Day Glasses. Optica's biography names sunglasses and scientific work as the initial major applications of Land's sheet polarizers, which soon found other uses.

A later Land patent, filed in May 1939 and granted in April 1941, describes making light polarizers from polyvinyl alcohol: a sheet of polyvinyl alcohol is softened, stretched (typically to between two and a half and eight times its original length) so that its molecules are aligned, and then stained with a solution of iodine and an iodide that forms a polarizing polyiodide. Land described the development of the material in a 1951 paper, "Some Aspects of the Development of Sheet Polarizers", in the Journal of the Optical Society of America.

Wire grids were studied as infrared polarizers by George R. Bird and Maxfield Parrish, whose paper "The Wire Grid as a Near-Infrared Polarizer" appeared in the same journal in 1960. In 2000, researchers at 3M described in Science multilayer interference stacks made from polymers with large birefringence, in which the refractive index difference in the thickness direction of the film controls the Brewster's angle at each layer interface; they noted that the materials and processes suit large-scale manufacturing. In 2017, 3M engineers described polymeric, birefringent multilayer reflective polarizers formed onto spherical, aspheric and freeform lens surfaces for pancake optics.

Applications in VR and AR

Liquid crystal displays

A liquid crystal display needs polarized illumination. With an absorbing entrance polarizer, at least half of the unpolarized backlight is lost; a reflective polarizing film placed behind the panel sends the wrong polarization back toward the light source, where part of it is converted to the usable polarization and recycled. 3M describes its Dual Brightness Enhancement Film (DBEF), a multilayer reflective polarizer film, as transmitting the polarization an LCD uses and reflecting the other back into the backlight, and claims efficiency gains of up to 30%.

In a 2022 review, Kun Yin, Shin-Tson Wu and co-authors explain that high-pixel-density LCDs for VR headsets have small aperture ratios; once the absorption of color filters and polarizers is added, the total light transmittance of the panel is only about 2%. See LCD for the use of LCD panels in headsets.

OLED panels

Many OLED panels carry a polarizer to stop the panel from reflecting external light. When Samsung Display announced its polarizer-free Eco² OLED in August 2021, it said a conventional polarizer reduces transmittance by more than 50 percent, and claimed from internal tests that removing it raised transmittance by 33 percent and cut power consumption by up to 25 percent. In VR headsets with pancake optics, a circular polarizer after the display panel is one of the components of the folded optical system.

Pancake lenses

Pancake lenses (polarized catadioptric optics or folded optics) depend on polarizers. Yin and colleagues list the typical components as a display panel, a circular polarizer, a half mirror, a magnifying lens, a quarter-wave plate and a reflective polarizer. Polarization decides whether the reflective polarizer reflects the light or lets it pass, and the half mirror folds the optical path three times before the light leaves toward the eye. The folded path allows a shorter gap between the lens and the display, which makes slimmer headsets possible. According to a 2017 3M paper, such optics were first described for immersive flight simulators, and using a reflective linear polarizer in place of one of the two beam splitters of the original design reduces the direct, not fully magnified transmission of the display image and increases contrast.

The reflective polarizer can be a metallic wire grid; the 3M paper cites an earlier head-mounted display eyepiece by Roger Huxford that used a plane wire-grid polarizer. The authors argue that polymeric birefringent multilayer polarizers have advantages: very low scattering and absorption, polarized reflectivity of up to 95% across a broad wavelength range at incidence angles from normal to plus or minus 60 degrees (after accounting for Fresnel reflections), low color shift, and films that can be formed into conic, aspheric and freeform lens surfaces. Because the light passes through the lens bodies several times, the paper also states that lenses in the cavity should be molded with minimum birefringence to keep a high degree of polarization through the folded path.

The polarization optics set the efficiency limits of the design. Jianghao Xiong and co-authors write that, with two incidences on the half mirror, maximum system efficiency is 25% for polarized input and 12.5% for unpolarized input, and that stray light from surface reflections and polarization leakage can cause visible ghost images; pancake headsets therefore usually show darker images with lower contrast than headsets with conventional refractive lenses. Yin and colleagues state that the folded path reduces optical efficiency about four times, and estimate that, to reach the 200 to 300 nits of a normal VR display, a display module behind pancake optics needs around 800 to 1,200 nits. See Ghost image and Stray light for these artifacts.

Meta's Meta Quest Pro used pancake lenses with what UploadVR, reporting Meta's description, called "more than 10 layers" of functional optical films. Meta wrote that "pancake lenses and polarization optics are in themselves nothing new", but that it had to build the supply chain for its lenses with industry partners because of the "incredibly precise lens and polarization film fabrication and integration" required.

LCoS light engines and AR combiners

An LCoS panel is a reflective display that modulates polarized light, while most light sources, including LEDs, are unpolarized. In an amplitude-modulating LCoS projector, a polarizing beam splitter separates the polarized light directed onto the panel from the modulated light, whose polarization the panel has changed, that goes on to the near-eye optics. Polarization conversion or recycling optics can be added to improve the light efficiency when an unpolarized LED is used. Xiong and colleagues note that a digital micromirror device does not need polarized light and so is generally more efficient than LCoS with an unpolarized source.

Yin and colleagues describe Google Glass as using a conventional polarizing beam splitter as its optical combiner with a field-sequential color LCoS panel of 640 x 360 pixels, a layout often called birdbath optics, and list HoloLens 1, Magic Leap 1 and Magic Leap 2 among AR products that use LCoS light engines. The polarizing beam splitter in such systems is covered in more detail in Beam splitter.

Polarized stereoscopic displays

Polarizing glasses can deliver separate images to the two eyes from a single screen: in a linear system one eye receives vertically polarized light and the other horizontally polarized light. Land's sheet polarizers were used in glasses for full-color stereoscopic movies. The history and variants of this method, including its use in immersive projection rooms, are covered in Polarized 3D system.

Research

In a 2024 paper in Opto-Electronic Advances, Yuqiang Ding, Zhenyi Luo, Garimagai Borjigin and Shin-Tson Wu proposed replacing the lossy half mirror of a pancake lens with a nonreciprocal polarization rotator. Their demonstration used a commercial Faraday rotator with reflective polarizers; they report that the theoretically predicted 100% efficiency can be approached with two high-extinction-ratio reflective polarizers, and that ghost images can be suppressed to an undetectable level if the optics have anti-reflection coatings. See also Anti-reflection coating.

In a SIGGRAPH 2020 paper, Andrew Maimone and Junren Wang of Facebook described VR display prototypes that combine holographic optics, directional backlighting, laser illumination and polarization-based optical folding; the prototypes were under 9 mm thick with a horizontal field of view above 90 degrees.

For optical see-through AR, Ruidong Zhu, Shin-Tson Wu and colleagues proposed in 2016 a "functional reflective polarizer" that works like a polarizing beam splitter but is more compact and lighter, combined with a polarization-independent guest-host liquid crystal cell that changes the see-through transmittance from about 73% to about 26% with 8 V and responds in about 50 ms, which they report is at least ten times faster than photochromic transition glasses. Polarization-selective liquid crystal elements, such as cholesteric liquid crystal reflectors that can replace the quarter-wave plate and reflective polarizer in a pancake lens, are reviewed by Yin and colleagues.

See also

• Birefringence
• Pancake lenses
• Beam splitter
• Polarized 3D system
• LCD
• Liquid crystal on silicon
• Optical combiner
• Ghost image
• Anti-reflection coating