Electro-optics is a branch of technology involving components, devices and systems which operate by modification of the optical properties of a material by an electric field. Thus it concerns the interaction between the electromagnetic (optical) and the electrical (electronic) states of materials.
The electro-optic effect relates to a change in the optical properties of the medium which usually is a change in the birefringence and not simply the refractive index. In a Kerr cell, the change in birefringence is proportional to the square of the electric field, and the material is usually a liquid. In a Pockels cell, the change in birefringence varies linearly with the electric field, and the material is a crystal. Non-crystalline electro-optic material have caught interested because of their low cost of production. It is polymer-based material, therefore is organic material. It is called sometimes as organic EO material, plastic EO material, or polymer EO material, which consists of a polymer and a nonlinear optical chromophore. Nonlinear optical chromophore is the molecule has Pockel's effect.