Optical spectra of VTE LiNbO3 : Cr

The luminescence in the region 13 350 13 900 cm(-1) of E-2 --> (4)A(2) tran sitions of Cr3+ are studied at 5, 50 and 80 K with congruent and stoichiome tric LiNbO3 : Cr (0.1 mol%) specimens are obtained using the Vapour Transpo rt Equilibrium (VTE) procedure. Twelve emission lines were observed in stoi chiometric crystals and 7 in congruent ones, Emission lines in VTE specimen s vs, congruent ones shift a little to lower energies and linewidth decreas es by about factor 2.5. The emission lines peaking at 13 420 and 13 540 cm( -1) seem to be depressed in congruent specimens and the emission line at 13 613 cm(-1) seems to be very weak in stiochiometric ones. Tn region 5-80 K; luminescence intensity decreases with temperature in congruent specimens, but increases VTE ones. A possible origin of the emission lines observed is discussed.