Sharp r-lines in absorption and emission of cr3+ in stoichiometric (vte) linb03

Abstract

R-line absorption and luminescence spectra of Cr3+ doped LiNbO3 show a distinct dependence on crystal stoichiometry. In the Cr3+ R-line region around 730 nm, up to five transitions can be observed in absorption and emission. In stoichiometric LiNb03:Cr crystals the line width (FWHM) in both absorption and emission decreases by about a factor of 2.5 in comparison with the same transitions in congruent samples. The emission line at lowest Energy in the R-line spectrum (A — 734.5 nm) disappears completely in stoichiometric LiNb03:Cr. This results, discussed together with models dealing with charge compensated Cr3+ pairs on Li and Nb sites and unpaired Cr3+ on Li site, is indicating a vanishing of the unpaired Cr3Li+with increasing [Li]/[Nb] ratio. Luminescence lifetime measurements in stoichiometric LiNbCO3:Cr reveal values similar to results for congruent material of r = 295 μs for the 731 nm line and τ= 268 μs for the 735 nm line, underlining the R-line character of these transitions. © 1995, Taylor & Francis Group, LLC. All rights reserved.