Polarization dependence of the luminescence properties of the erbium doped KNbO ₃ ferroelectric ceramics

The polarization dependence of the Stokes photoluminescence (PL) spectra of erbium doped Potassium niobate (KNbO ₃) ceramics has been investigated by studying the relations between PL spectra with the poling electric field, poling time. All the Stark splitting components of ⁴S _3/2 → ⁴I _15/2 transition were evident after the poling process. The experiments also showed that the polarization enhances the fine structure and modifies the intensity ratio of the ⁴S _3/2 → ⁴I _15/2, ⁴F _9/2 → ⁴I _15/2 and the ⁴S _3/2 → ⁴I _3/2 transitions at different poling electric fields and poling times. From the similar tendency between the frequency shift of PL spectra ^Δv and the planar electromechanical coupling factor Kp demonstrate indirectly that the Stark splitting was produced by the dipole moment of erbium ions state interacting with the internal local electric field due to polarization.