Explanation

Under the action of external electric field, the change of refractive index of electro-optical materials is proportional to the intensity of external electric field. This effect is called paul kerrs or primary electrophoto effect and linear electrophoto effect. The materials presenting this effect is called Pockels materials. There are many kinds of such materials, including inorganic materials and organic materials - but inorganic crystal are mainly of practical significance. They can be divided into four types according to crystal structure: potassium dihydrogen phosphate type, ilmenite type, tungsten bronze type and sphalerite type. The common feature of crystal structure is that there is no symmetry center. It is required to have large electro-optic coefficient, high refractive index, small dielectric constant and optical absorption coefficient. Actual materials often have important differences in light damage resistance, coefficient of thermcal expansion, light transmission range, temperature stability, chemical stability and availability, which must be selected according to specific use conditions. Pockels materials is the most commonly used and therefore the most important electro-optical materials. When used, it can induce refractive index changes in crystal through different device configurations, crystal orientation and the direction of applied electric field relative to the polarization of incident light, thus realizing the modulation of laser intensity, phase or polarization.

Classification