Comparative studies of luminescence in congruent and stoichiometric VTE-treated linbo₃:Cr

Abstract

The luminescence spectra of Cr³⁺ impurity have been studied in the wide spectral (11500 to 13900 cm⁻¹) and temperature (5 to 300K) ranges for initially congruent grown LiNbO₃:Cr³⁺ (0·1% mol.) specimens. The samples were further stoichiometrised using the Vapour Transport Equilibrium (VTE) procedure. In contrast to the congruent samples, for which in the region of supposed ²E-⁴A₂ transitions in Cr³⁺ ions 7 emission lines were detected, 12 emission lines were observed in stoichiometric VTE specimens. Moreover, in VTE crystals, we observed 5 so far unknown polarized lines centered at 12801, 12530, 12215, 11980 and 11720 cm⁻¹ (T=80K) on the short-wavelength side of ⁴T₂- ⁴A₂ emission band. These new lines can be tentatively attributed to transitions in exchange-coupled pairs of Cr³⁺ ions.

Key Words:

• Keywords: LiNbO₃
• Cr³⁺ centers
• luminescence