Polarization Introduction to and Definition

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 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

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

Applications for Polarization

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.

About American Polarizers Inc.

At API, we take pride in providing the highest level of customer service, leading-edge technical knowledge, and stringent quality control. In addition to competitive prices, we offer many value-added services, such as inventorying custom products and just-in-time delivery. Quality is our culture, not just in product production, but the level of attention and care that customers can expect to receive. That quality is backed by industry-best quality certifications and standards, including ISO 9001:2015 designation.

When quality counts, count on API.

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