The modulation of optical properties of a material can be exploited for a number of "intelligent" optoelectronic devices such as switches,logic gates and memory.

Certain materials change their optical properties when subjected to an electric field.This is caused by forces that distort the positions, orientations, or shapes of the molecules consistuting the material.The Electro-Optic Effect is the change in the refractive index resulting from the application of a DC or low-frequency electric field.A field applied to an anisotropic electro-optic material modifies its refractive indices and thereby its effect on polarized light.

The refractive index of an optical medium is altered by the presence of sound.Sound is dynamic strain involving molecular vibrations that take the form of waves which travel at a velocity chracteristic of the medium.The simplest form of interaction of light and sound is the partial reflection of an optical plane wave from the stratified parallel planes representing the refractive-index variations created by an acoustic plane wave. This form of light-sound interaction is known as Bragg diffraction and the device is called Bragg cell.

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