Pockels effect

In optics, the Pockels effect, or Pockels electro-optic effect, is a directionally-dependent linear variation in the refractive index of an optical medium that occurs in response to the application of an electric field. It is named after the German physicist Friedrich Carl Alwin Pockels, who studied the effect in 1893. The non-linear counterpart, the Kerr effect, causes changes in the refractive index at a rate proportional to the square of the applied electric field. In optical media, the Pockels effect causes changes in birefringence that vary in proportion to the strength of the applied electric field.

The Pockels effect occurs in crystals that lack inversion symmetry, such as monopotassium phosphate (KH₂PO₄, abbr. KDP), potassium dideuterium phosphate (KD₂PO₄, abbr. KD*P or DKDP), lithium niobate (LiNbO₃), beta-barium borate (BBO), barium titanate (BTO) and in other non-centrosymmetric media such as electric-field poled polymers or glasses. The Pockels effect has been elucidated through extensive study of electro-optic properties in materials like KDP.