Kerr Effect

What Does Kerr Effect Mean?

The Kerr effect is a phenomenon in which the refractive index of a material changes because of an applied electrical field, and the change in the refractive index is proportional to the square of the applied electric field. The Kerr effect is best observed in materials known as Kerr mediums, centrosymmetric materials like liquids, gases and some crystals, although most materials show the Kerr effect to some extent when subjected to an electrical field.


The Kerr effect has been applied to digital photography to create a type of shutter with very short exposures and rapid reaction.

The Kerr effect is also known as the quadratic electro-optic effect (QEO effect).

Techopedia Explains Kerr Effect

The Kerr effect was discovered by John Kerr in 1875. It is weaker compared to the Pockels effect, which changes the refractive index varies linearly to the value of the applied electrical field. Both the Kerr and Pockels effect are applied in components that are used in optical signal-processing applications and on optical communications as a whole.

The Kerr effect has two types:

  • Electro-Optical Effect: Through the slow application of an external, varying electrical field to a Kerr medium, the material will develop two indexes of refraction. One is for light that is polarized parallel to the electric field, while the other is for polarized light perpendicular to the field.
  • Magneto-Optic Kerr effect (MOKE): The phenomenon in which light exhibits a slightly rotated plane of polarization when reflected from a magnetized material.

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Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.