Energy Level Splits Of Cr³⁺ Ions In The LiNbO₃ Crystal Field

The LiNbO₃ crystal was a multifunctional material in photoelectric industry. As a broadly studied and used luminescence ion, Cr³⁺ had two stronger absorption bands around 470nm and 660nm. Recently, attention on the Cr³⁺: LiNbO₃ crystal has been attracted more and more, due to its potential tunable laser in a broad band, together with the excellent photoelectric properties of LiNbO₃ crystal.The basic theories on group theory and crystal field theory were introduced in the foreside work of this paper. As an example of the application of these theories, the terms of nd3 configuration was established under a weak Oh field, wish the ground state of 4A2. Many theoretical and experimental researches show that the strong field theory should be used when studying the electronic states of some transition elements such as Fe,Cr and others. So that, the strong field theory combining with experimental data has be used to study the energy level splits of Cr³⁺ ions in LiNbO₃ crystals in the chapter 4 and chapter 5. In the chapter 4, the Hamiltonian matrix of Cr³⁺ ions in LiNbO₃ crystals was acquired. The measurements and the calculations of absorption spectra of 0.2 mol.% Cr³⁺: LiNbO₃ crystals were carried out in Chapter 5. Two absorption peaks at 482nm and 655nm are displayed, which is corresponding to the transition of 4A2→4T1 and 4A2→4T2 , respectively. The crystal field parameter of Dq and Racah parameters B and C were calculated and list in the following table.Because of the D_q/B= 2.87> 2.3 , it could be concluded the crystal field of Cr³⁺ in LiNbO₃ crystals was really strong. By putting Dq and Racah parameters into Hamiltonian matrix every energy term of Cr³⁺:LiNbO₃ was acquired finally, which is consistent with the experiments well.