Crystal field analysis and low lying energy levels for Cr³⁺ doped in LiNbO₃

Due to its numerous optical applications, Cr³⁺-doped lithium niobate LiNbO₃ is an extensively studied material. Despite a large number of the experimental and theoretical studies of this system, still there exists an ambiguity regarding the nature of the Cr³⁺ impurity centers. In the present work we report on the detailed crystal field parameters and energy levels calculations of the CrLi³⁺ positions. The exchange charge model of crystal field was used to calculate the crystal field parameters with taking into account the effects of the covalent bond formation between the Cr³⁺ and O^2- ions. The calculated CFP values were used for diagonalization of the Cr³⁺ crystal field Hamiltonian in a complete basis set spanned by all wave functions of LS terms of the 3d³ electron configuration. The calculated energy levels are in good agreement with the experimental data available in the literature.