Electro-optic modulator

device that can quickly change the phase of an optical beam according to an applied voltage

An Electro-optic modulator is an optical device. It is made of a material that has a so-called electro-optical effect. This means that the material changes its optical properties when there is an electric field. One example is then when there is no electricity, light can pass through, and when there is, it cannot, and is reflected.