The development of birefringence when an isotropic transparent substance in placed in an electric field. It is used in constructing Kerr cells, which function as variable wave plates with an extremely fast response time, and find use in high-speed camera shutters. Because the effect is quadratic with respect to E, is sometimes known as the quadratic electrooptical effect.
The amount of birefringence (as characterized by the change in index of refraction due to the Kerr effect can be parametrized by

where K is the Kerr constant (in cgs units of cm statv and is the vacuum wavelength.The phase change introduced in a Kerr cell of thickness d under an applied voltage V is given by