What is the Pockel's effect?

Both our phase and our amplitude modulators are based upon the Pockel's effect: the electro-optic effect where the refractive index along one or more axes is proportional to an externally applied electric field. Therefore, by applying a voltage across the electrodes of an electro-optic crystal, you can change the phase of light as it passes through the crystal. By placing the crystal between crossed polarizers, this phase modulation can be converted into amplitude modulation.