Abstract:

In order to investigate the spectral properties of the Cr3+ in Ca₃Al₂Ge₃O₁₂: garnet, the polycrystal material Ca₃Al₂Ge₃O₁₂:Cr³⁺ was synthesized; its X-ray diffraction patterns, diffuse reflection spectra, excitation and emission spectra were measured. The spectral properties of the material were discussed and the crystal field strength (Dq/B), Stokes displacements(ΔEs) along with Huang-Rhys factors(S) were calculated. Under the excitation of 450 nm light, the emission spectrum of Cr3+ in Ca3Al2Ge3O12 garnet at room temperature mainly consists of three broad bands with weak R line. Three broad bands correspond to 4T1-4A2, 4T2-4A2, and 2T2-4A2 transitions of Cr³⁺ ions, respectively. The R line becomes stronger and sharper at low temperature of 30 K. The calculated results showed Dq/B=2.43, ΔEs=1884 cm-1 and S=5.21, indicating that Cr³⁺ ions in Ca₃Al₂Ge₃O₁₂: garnet locate at weaker crystal field strength and the coupling between the electrons and the phonons is strong. The results imply that Ca₃Al₂Ge₃O₁₂:Cr³⁺ would be a promising material for tunable laser.

Key words: Spectroscopy;Cr3+ doped calcium aluminium germanate garnet;Broad-band emission;Crystal field parameter;Tunable laser material