We have studied Cr3+ emission in LiNbO3 crystals with compositions close to
stoichiometry, which were not investigated up to now. The emission spectra
recorded at low temperature exhibits new peaks at 13555 and 13415 cm(-1) T
he measurement of the fluorescence decays and the recording of the excitati
on spectra monitored at all the emission peaks were performed in order to d
etermine the different Cr3+ centres in lithium niobate as well as their ene
rgy levels contributing to the emission experiments. Three Cr3+ centres per
mit to describe the various features of the emission spectra. The main cent
re corresponds to the weak crystal field scheme and yields the broad emissi
on band as well as the new peaks which have a vibronic origin. The two othe
r Cr3+ centres agree with the high crystal field scheme and display the sha
rp R-lines at 13685 and 13614 cm(-1). (C) 1999 Published by Elsevier Scienc
e B.V. All rights reserved.