Chromium centers in stoichiometric LiNbO3

The nature of Cr3+ center in LiNbO3 has been the subject of intense discuss ions in recent years. Partly, contradictory assignments of the centers resu lted from intrinsic defects in the so-called congruent samples. More recent ly, stoichiometric samples, produced via the VTE process, have become avail able and show a largely reduced number of Cr sites. In this paper we presen t new spectroscopic data on a stoichiometric LiNbO3 :Cr3+ Sample produced u sing the HTTSSG process. This sample shows an even further reduced number o f lines in the so-called R-line region. In addition, the study of this samp le sheds new light on the origin of near infrared emission lines first disc overed in LiNbO3 : Cr : Mg, which might be due to Cr3+-Nb4+ pairs. All emis sion lines show an unprecedented small line width, which allows high-resolu tion studies on this fascinating system. (C) 2000 Elsevier Science B.V. All rights reserved.