Electrooptic

Electrooptic refers to phenomena and materials in which the optical properties of a medium, particularly its refractive index, change in response to an electric field. The most studied effects are the electro-optic effects, notably the Pockels effect (linear electro-optic) and the Kerr effect (quadratic electro-optic). In the Pockels effect, the induced change in refractive index is proportional to the applied electric field and is described by an electro-optic tensor. The Kerr effect produces a change proportional to the square of the field and is typically weaker but observable in a broader range of materials, including some centrosymmetric crystals.

Electrooptic materials are used to construct devices that modulate or control light. Common materials include lithium niobate (LiNbO3) and lithium tantalate (LiTaO3), which are widely used in optical modulators and frequency conversion. Other notable electrooptic crystals include potassium dihydrogen phosphate (KDP) and beta barium borate (BBO). In addition to inorganic crystals, organic electrooptic polymers and liquid crystal systems offer large electro-optic coefficients and are explored for integrated and flexible photonics. Some devices employ thin-film or waveguide configurations to enhance interaction between light and the electric field.

Applications span fiber-optic communications, where electro-optic modulators encode information onto light, to laser systems for phase, amplitude, or Q-switching control. In integrated photonics, electrooptic effects enable compact, high-speed modulators and switches for optical networks, sensing, and display technologies. The field continues to evolve with advances in material science and device engineering to achieve higher bandwidth, lower voltage operation, and broader wavelength coverage.