Temperature dependence of the refractive index in BaTiO₃ and photorefraction in perovskite oxides

Abstract

The optical refractive index of BaTiO₃ in the paraelectric phase is calculated. The anomaly of the optical refractive index is attributed to the electron-phonon interaction which causes deviation from a linear temperature dependence of the band gap at T>T₀ (T₀ is the cubic-tetragonal phase transition temperature). Photorefraction related to optically generated carriers (photodoping) in perovskite oxides is considered within the microscopic electron-phonon theory taking into account also the impurity states. The photodoping and recharging of impurities lead to a change of spontaneous polarization and birefringence.

Key Words:

• Ferroelectricity
• perovskite oxides
• refractive index
• photorefraction