Electro-optic effect
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The electro-optic effect is a change in the optical properties of a material in response to an electric field that varies slowly compared with the frequency of light. The term encompasses a number of distinct phenomena.
Two of the most important electro-optic effects having application as modulation mechanisms in optical communication are the Pockels effect and the Kerr effect, in which birefringence is induced or modified by an electric field. The Pockels effect is a change in refractive index or birefringence that depends linearly in the field. Only certain crystalline solids show the Pockels effect, as it requires inversion asymmetry. The Kerr effect is a change in index or birefringence that is quadratic in the field. All materials display the Kerr effect, with varying magnitudes, but it is generally much weaker than the Pockels effect.
The term "electro-optic" is often erroneously used as a synonym for "optoelectronic."