Polarization Introduction and Definition by American Polarizers

American Polarizers Inc. (API) is globally known for polarization products and solutions used across a broad range of industries, including research, aerospace, 3D imaging, medical, machine vision, photo, and more.

Our expertise in polarization is backed by industry-best quality certifications and standards. Whether you’re inventorying previous orders or seeking a brand new product solution, you can count on API to fulfill your order using the most stringent quality standards in the industry.

Regardless of your imaging needs, it’s essential for you to understand the physics behind the manipulation of polarizing light for optical design. While a focus on the wavelength and intensity of light is important, polarization is frequently neglected.

A lack of polarization can negatively impact everything from laser beams and filters to microscopes and LCD screens.

What Is Polarization?

Polarization is a phenomenon that is observed in certain electromagnetic radiations, including light waves. In a polarized light wave, the direction and magnitude of the vibrating electric field are related in a specified way. This is in contrast to unpolarized light waves, in which the direction of the electric field fluctuates randomly in time.

Light waves are transverse, which means that the vibrating electric vector associated with each wave is perpendicular to the direction of propagation. The orientation of the electric field vector determines the polarization state of the light wave. The polarization axis of a light wave is the direction of the electric field vector.

Linear polarization is a common type of polarization, in which the electric field oscillations occur in a single plane. The direction of polarization is the direction of this plane. In vertically polarized light, the electric field oscillates vertically, while in horizontally polarized light, the electric field oscillates horizontally.

Circular polarization is another type of polarization, in which the electric field vector rotates in a circular pattern as the wave propagates. Circular polarization can be either right-handed or left-handed, depending on the direction of rotation.

The polarization state of a light wave can be described mathematically using polarization density. This is a vector quantity that describes the amplitude and phase of the electric field vector in each direction of polarization.

Understanding polarization is important in many areas of science and technology, including optics, seismology, radio, and microwaves. It has applications in technologies such as lasers, wireless and optical fiber telecommunications, and radar.
Applications of Polarization

Polarization has a wide range of applications in various fields. In this section, we will discuss some of the most notable applications of polarization.

What is Light?

There are a few ways to understand light. In the simplest of terms, light is a form of radiation called an electromagnetic wave. More specifically, light can also be defined as a form of energy with two types of nature made up of photons that are like participles but have properties that are also wavelike.

Photons carry a fixed amount of energy that depends on the wavelength of light. The shorter the wavelength, the more energy a photon possesses. Theoretically, light has no mass, yet, with its dual nature, it can simultaneously act as a particle and a wave.

The Visible Light Spectrum

As radiant energy, light-energy waves travel in a straight line. The visible light of electromagnetic spectrum falls within specific wavelengths ranging from about 380 to 750 nanometers.

Depending on the wavelength reflected when light hits a surface, you’ll see a particular color. There are seven colors that make up the visible spectrum from longest to shortest wavelength: red, orange, yellow, green, blue, indigo, and violet. When all colors in the spectrum are combined, you see white. According to the Wave Theory, light is an electromagnetic wave containing visible light as well as x-rays, UV rays, infrared rays, gamma rays, etc.

Light travels at about 186,000 miles per second. Most light is not visible to the naked eye and thus falls outside of the visible wavelength spectrum.

The Difference Between Unpolarized and Polarized Light

Light waves, which have both an electric and magnetic component, are produced when electric charges vibrate. The waves oscillate perpendicularly to the direction of propagation. When a light wave fluctuates randomly in multiple planes, it’s called unpolarized light.

Unpolarized light includes natural and artificial light, including the sun, candlelight, incandescent lightbulbs, neon lights, LEDs, etc. In contrast, polarized light is when the wave fluctuates in a single plane so that the electric field is well defined.

Examples of polarized light include that emitted from lasers, glass, calm water, the surface of a highway, etc. Three types of polarized light are classified based on how the electric field is oriented.

  • Elliptical Polarization – the electric field of light describes an ellipse (most common)
  • Linear Polarization – the electric field is confined to a single plane along the direction of propagation
  • Circular Polarization – the electric field consists of two linear components that are perpendicular to each other

Applications of Polarization

Polarization has a wide range of applications in various fields. In this section, we will discuss some of the most notable applications of polarization.

In Photography

Polarizers are commonly used in photography to reduce glare and improve color saturation. A polarizing filter can be used to control the amount of polarized light that enters the camera lens. By rotating the filter, the photographer can selectively eliminate reflections from non-metallic surfaces such as water or glass. This results in a clearer image with more vibrant colors.

In Astronomy

Polarization is also used in astronomy to study the magnetic fields of stars and galaxies. The polarization of light from distant objects can reveal information about the magnetic fields that the light has encountered on its journey through space. Astronomers use polarimeters to measure the polarization of light from celestial objects.

In Organic Chemistry

Polarimetry is a technique used in organic chemistry to determine the concentration, purity, and identity of chiral molecules. Chiral molecules are molecules that are non-superimposable mirror images of each other. Polarimetry measures the rotation of plane-polarized light as it passes through a sample containing chiral molecules. This technique is widely used in the pharmaceutical industry to ensure the quality and purity of drugs.

In Spectroscopy

Polarization is also used in spectroscopy to study the properties of materials. By measuring the polarization of light that is absorbed or emitted by a material, researchers can determine the molecular structure and composition of the material.

This technique is particularly useful in the study of biological molecules such as proteins and DNA.

In 3D Movies

Polarization is used in 3D movies to create the illusion of depth. Two images of the same scene are projected onto the screen, each with a different polarization orientation. The viewer wears polarized glasses that allow each eye to see only one of the images. This creates the perception of depth and a three-dimensional image.

In conclusion, polarization has a wide range of applications in various fields, including photography, astronomy, organic chemistry, spectroscopy, and 3D movies. By selectively filtering polarized light, researchers and professionals can gain valuable insights into the properties of materials and create stunning visual effects.

The ability to control polarization is useful in many imaging applications. Polarizers can be placed over a light source and lens for increasing color and contrast effects, reducing reflective hot spots and glare, glass and plastic stress evaluation, organic chemical compounds identification, and polarization microscopy.

Polarization Solutions by Industry

You can turn your most innovative ideas into reality with our polarizing materials and polarization solutions for a wide range of applications, including aerospace, imaging, computer vision, motion picture video and still cameras, passive 3D, inspection, biomedical, nondestructive testing, quality control and testing, and measurement applications.

Polarization Articles and Resources

Discover articles, charts, and graphs that make it easy to understand the basics of polarization. Polarization is an important factor to consider when designing optical products. Learn how you can control the wavelength and intensity of light with API’s high-quality polarization solutions.

Polarization of Light

Unpolarized light can be manipulated to become polarized light by transmission, reflection, refraction, and scattering. Polarization can be accomplished in a few ways using materials from expensive large, pure crystals to inexpensive stretched plastic.


Polarizers select specific polarized light while leaving the rest to be either transmitted, reflected, or absorbed.

  • Reflective Polarizer – transmits a specific polarization of light and reflects the rest (e.g., wire grid polarizers, Brewster’s angle)
  • Dichroic Polarizer – absorbs a specific polarization of light and transmits the rest (e.g., modern nanoparticle polarizers)
  • Birefringent Polarizer – selects polarization of light that refracts at different angles based on the refractive index

Waveplates (or Retarders)

Waveplates modify existing polarizations without the beam being attenuated, deviated, or displaced. They retard (or delay) a component of polarization based on its orthogonal component.

  • Half-Wave Plate – shifts the polarization direction of linearly polarized light
  • Quarter-Wave Plate – converts linearly polarized light to or from circularly polarized light

Frequently Asked Questions

How can electromagnetic waves be polarized?

Electromagnetic waves can be polarized by filtering out all but one direction of oscillation. This is typically done using a polarizing filter, which only allows waves with a particular orientation of the electric field to pass through.

What is linear polarization?

Linear polarization is a type of polarization in which the electric field oscillates in a single plane. This is in contrast to circular polarization, in which the electric field rotates around the axis of propagation.

What are some examples of polarization?

There are many examples of polarization in the natural world. Light reflecting off of a flat surface, such as water or a road, is often polarized. Some animals, such as bees, use polarization to navigate. In physics, polarization is used to describe the orientation of the electric field in electromagnetic waves.

What is the significance of polarization in physics?

Polarization is an important concept in physics, as it describes the orientation of the electric field in electromagnetic waves. This has important implications for how waves interact with matter, and is used in many different areas of physics, from optics to solid-state physics.

How is polarization affected by reflection?

When light is reflected off of a surface, it can become polarized. The degree of polarization depends on the angle of incidence and the properties of the reflecting surface. For example, light reflecting off of a flat surface at a particular angle will be completely polarized in the plane of reflection.

What is the polarization formula?

The polarization formula is a mathematical expression that describes the degree of polarization of an electromagnetic wave. It is typically written as a ratio of the difference between the maximum and minimum amplitudes of the electric field to the sum of those amplitudes. This formula is used in many different areas of physics, from optics to solid-state physics.

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