Electro-optic cofficient

The electro-optic coefficient is a measure of the changability optical activity of a material when an electric field is applied.

<math>r_{33} = \beta(\epsilon,\omega)N<cos^3\theta>\,\!</math>

where

<math>\beta(\epsilon,\omega)\,\!</math> is the molecular first hyperpolarizability which at a give wavelenth ω

<math>N<cos^3\theta>\,\!</math> is number density