Stark effect on Cr3+ spectra in LiNbO3

The electric field effect on the absorption spectra of Cr3+ impurity centers in LiNbO3 has been investigated at 77 K using a sensitive modulation method. A linear Stark effect on B- and R- absorption lines of Cr3+ was observed for a field applied along the trigonal crystal axis Z, and no effect was detected when field was normal to Z. Such properties establish that the permanent dipole moments of the observed Cr3+ centers are oriented alone the trigonal crystal axis proving their C-3 point symmetry. The quantitative characteristics of the held effect are obtained. The marked peculiarity of the Stark effect in LiNbO3:Cr3+ is the opposite sign of the electric field shift of B-1 and B-2 lines.