Pockels Effect

(also electrooptical effect), the change in the index of refraction of light in crystals placed in an electric field, the change being proportional to the intensity of the field. The effect is observed only in piezoelectric materials. It was first discovered in 1894 by the German physicist F. C. Pockels but for a long time thereafter was little studied and found limited application. This was due chiefly to the high voltages—on the order of hundreds of kilovolts—needed to obtain an appreciable effect.

The emergence of lasers stimulated the study of the Pockels effect, which in turn has been used in the development of a number of devices for controlling coherent optical radiation electrically. Almost all light modulators are based on the Pockels effect. It has the important property of low inertia, which permits light to be modulated up to frequencies of approximately 10¹³ hertz. Moreover, because of the linear dependence of the refractive index on the intensity of the electric field, the nonlinear distortion incurred in modulating light is fairly low. The low inertia allows the use of the effect in modulating the quality factor of lasers and thus obtaining light pulses of short duration and high power. The effect is also used in systems that deflect light beams and in devices that produce two-dimensional optical images.