How does birefringence occur in electro-optical ceramic materials?

In electro-optical ceramic materials, birefringence occurs as a result of the material's response to an applied electric field, which induces a change in its optical properties.12

Birefringence is defined as the difference between the refractive index measured parallel to the optical axis of the crystal and the refractive index measured perpendicular to that axis. Because light propagates at different velocities in these two directions, a phase shift is introduced as the light passes through the material.1

In electro-optical ceramics, this phase shift is voltage-dependent. When an external electric field is applied, it alters the material's internal polarization, which in turn modifies the refractive index. This phenomenon allows for the precise control of light, making these materials essential for components such as optical switches, modulators, and demodulators used in high-speed communications. While some materials exhibit this effect linearly (the Pockels effect), others respond proportionally to the square of the applied field (the Kerr effect).132