The technology associated with those components, devices and systems which are designed to interact between the electromagnetic (optical) and the electric (electronic) state. Note 1: The operation of electro-optic devices depends on modification of the refractive index of a material by electric fields. Note 2: In a Kerr cell, the refractive index change is proportional to the square of the electric field, and the material is usually a liquid. Note 3: In a Pockels cell, the refractive index change varies linearly with the electric field, and the material is a crystal. Note 4: "Electro-optic" is often erroneously used as a synonym for "optoelectronic".