Kerr Effect


The Kerr Effect, also known as the quadratic electro-optic effect, is a change in the refractive index of a material in response to an applied electric field. This effect causes a rotation in the plane of polarization of light when it passes through certain transparent materials under influence of an electric field. It is named after the Scottish physicist John Kerr who discovered it in 1875.


The phonetics of the keyword “Kerr Effect” would be: “kur ih-fekt”

Key Takeaways

  1. The Kerr effect, named after John Kerr, is a phenomenon where the refractive index of a material changes in response to an applied electric field. This change in refractive index leads to a change in the polarization state of a light wave traveling through the material.
  2. There are two types of Kerr effect: the quadratic, or DC Kerr effect, and the linear, or AC Kerr effect. The DC Kerr effect occurs in all materials and depends on the intensity of the light, while the AC Kerr effect is observed only in some materials and depends on the electric field of the light wave.
  3. The Kerr effect has numerous applications in optical devices. Some of these include optical modulators, which use the Kerr effect to control the intensity, phase, polarization, or path of a light beam, and optical switches, which modulate light signals in optical communication systems.


The Kerr Effect, also known as the quadratic electro-optic effect, is crucial in technology as it plays a significant role in various optical and telecommunication applications. The heart of the Kerr Effect is the ability to alter the properties of a material, such as its refractive index, when subjected to an electric field.

This principle is key in creating many electro-optic devices like modulators and switches, paramount in telecommunications for regulation of signal intensity, phase, and polarization of light waves. The Kerr Effect also facilitates the development of magneto-optic storage devices, optical isolators, and electric field sensors, making it an indispensable aspect of current and future optical technologies.


The Kerr Effect, also known as the Quadratic Electro-Optic Effect (QEO effect), is a key principle in optical technology that is imperative for numerous applications in both scientific and industrial contexts. Essentially, the Kerr Effect refers to the alteration of the refractive index of a material as a result of the application of an electric field.

In simplified terms, it influences how a material interacts with light when an electrical charge is introduced, thus changing the path of light. The applications of the Kerr Effect are numerous and varied. In telecommunications, it finds use in optical fiber communications where alterations in light pathways help with the transmission and reception of data signals. Moreover, the Kerr Effect principle is employed in optical data storage technology, like compact discs and DVDs, where light is used to interpret stored information.

Furthermore, in the realm of scientific research, the Kerr effect is used in high-intensity laser physics and quantum computing to manipulate the pathways of lasers and photons respectively. Thus, the Kerr Effect is a fundamental concept in optics that greatly influences numerous existing technologies.


1. Optical Communication: Kerr effect plays a significant role in optical communication systems. It affects light signals in optical fibers as it changes the refractive index of the medium through which the light passes. This phenomenon is utilized in fiber optics technology, impacting the transmission of data through light signals.

2. Laser Physics: In laser physics, the Kerr effect is used for mode locking, in which a laser can be made to produce pulses of light of extremely short duration, typically around picoseconds to femtoseconds. The non-linear response of the medium (due to the Kerr effect) to the intense light contributes to an automatic synchronization of the modes, resulting in a pulsed emission.

3. Telecommunications and Signal Processing: The Kerr effect is used in telecommunications for all-optical signal processing, especially switching techniques. With the help of the Kerr effect, data signal can be switched from one channel to another without the need of converting it into an electric signal, thereby improving the speed and efficiency of digital communication systems.

Frequently Asked Questions(FAQ)

Q: What is the Kerr Effect?

A: The Kerr Effect is a phenomenon in the field of optics where the refractive index of a material is modified with the presence of an electric field. This effect is named after the British physicist John Kerr who discovered it.

Q: How was the Kerr Effect discovered?

A: John Kerr, a Scottish physicist, discovered the Kerr Effect in 1875 during his experiments on the reflection of light. He found out that the plane of polarized light changes when reflected at the pole of a magnet.

Q:What are the types of Kerr Effect?

A: There are two types of Kerr Effect: the magnetic Kerr effect and the electric Kerr effect. The magnetic Kerr effect is divided into two categories: longitudinal and transverse. On the other hand, the electric Kerr effect is broken down into two categories: optical and electro-absorption.

Q: How does the Electric Kerr Effect work?

A: The Electric Kerr Effect occurs when a material’s refractive index changes due to an applied electric field. The higher the electric field, the greater the change in the refractive index.

Q: How does the Magnetic Kerr Effect work?

A: The Magnetic Kerr Effect is an optical property observed when a light is reflected off a magnetised surface. The plane of polarization is influenced by magnetic properties of the material the light reflects off of.

Q: In what fields is the Kerr Effect used?

A: The Kerr Effect is widely used in the fields of telecommunications, material science, and data storage. It’s particularly useful for investigating magnetic materials, or to encode and retrieve data in optical memory devices.

Q: What is a Kerr cell?

A: A Kerr cell is an optical device that takes advantage of the Kerr effect for modulating light. It was widely used in early television systems before being replaced by more efficient technologies.

Q: How do I observe the Kerr Effect?

A: The Kerr Effect can be observed using specific equipment in a controlled environment, such as a laboratory. You need to apply an electric field or a magnetic field to a material while shining polarized light through or onto it and then detect the changes in the refractive index or light orientation.

Related Tech Terms

  • Nonlinear Optics
  • Electromagnetic Radiation
  • Polarization
  • Light Refraction
  • Optical Phenomena

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