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Electro-optic Effect

Definition: the phenomenon that the refractive index of a material can be modified with an electric field

Alternative term: Pockels effect

German: elektrooptischer Effekt

Categories: nonlinear optics, physical foundations

Cite the article using its DOI: https://doi.org/10.61835/14x

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The electro-optic effect (or electrooptic effect) is the modification of the optical phase delay (often described with its refractive index) of a medium, caused by an electric field. Some authors more generally consider electro-optic effects such that any optical properties may be affected by an electric field – for example, it may also be a change of absorption characteristics, such as through the Franz–Keldysh effect as used in electroabsorption modulators. In this article, only phase effects.

Only non-centrosymmetric materials (mostly nonlinear crystal materials) exhibit the linear electro-optic effect, also called the Pockels effect, where the refractive index change is proportional to the electric field strength (see the article on Pockels effect for more details).

Only materials exhibiting the Pockels effect are called electro-optic materials. Some examples of such materials are lithium niobate (LiNbO₃), lithium tantalate (LiTaO₃), potassium titanyl phosphate (KTP) and β-barium borate (BBO).

All centrosymmetric media exhibit only the Kerr electro-optic effect, also called Kerr effect, where the refractive index change is proportional to the square of the electric field strength, and is typically much weaker than for the linear effect within the range of electric field strength which the material can tolerate. However, there are special cases where a giant quadratic electro-optic effect is observed [1].

Most devices in electro-optics are based on the linear electro-optic effect. It is exploited in Pockels cells, which can be part of electro-optic modulators, and for electro-optic sampling.

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Bibliography

[1]	M. M. Jahanbakhshian et al., “Giant electro-optic coefficient in a graphene oxide film”, Opt. Lett. 47 (11), 2798 (2022); https://doi.org/10.1364/OL.451503

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