Oct 10 2013
The Kerr effect (also known as quadratic electro-optic effect) is a phenomenon observed in non-linear optic materials where the refractive index of the material changes in response to an electric field. This effect is observed in all materials; however, it is more prominent in certain liquids. John Kerr, a Scottish physicist, discovered it in the year 1875.
The Kerr or quadratic electro-optic effect (QEO) effect can be of two types: the Kerr electro-optic effect and the optical Kerr effect. In the first type, a varying DC field is applied on the material and in the second type the light source itself acts as an AC source. The following sections will elaborate on the working, experimental set up and applications of the optical Kerr effect.
Experimental Set Up
The optical Kerr effect is more prominent in liquids. When an electric field is applied on a Kerr media (mostly liquids), the liquid molecules tend to align themselves with the electric field. Typical values of applied electric field are 108 V/m. This causes a change in the refractive index of the medium and the material turns birefringent. Thus, incident light is modulated when passed through a Kerr medium.
Polar liquids like nitrotoulene have very large Kerr constants and hence respond very quickly to the applied electric field.
Working
There are two types of Kerr effects: electro-optic and optical Kerr effect. The working of both the types is described below:
Electro-optic Kerr effect – in this type, a varying DC electric field is applied to the non-linear optic medium, resulting in the perturbation of the refractive index of the material. As a result, the material acts as a waveplate that polarizes light in a desired direction.
Optical Kerr effect – this is a self-induced effect, where the incident light creates an electric field.
Applications
Some of the areas of application of the Kerr effect are listed below:
- Waveguides
- Spectroscopy of liquids
- Optical hetrodyne creation
References