Spectral characteristics and crystal field parameters of the Cr3+ doped Cd3Al2Ge3O12

Abstract

Polycrystalline Cd3Al2Ge3O12：Cr3+ was synthesized by high temperature solid-state method. Its crystal structure was analyzed by X-ray diffraction. Based on its absorption spectrum at room temperature and the emission spectra at room temperature and 77K， the spectral properties were investigated and the crystal field parameter was calculated. The results show that under the excitation of 450nm light， the emission spectrum of Cd3Al2Ge3O12：Cr3+ at room temperature mainly consists of three broad bands with a weak R line. The three broad bands correspond to 4T1→4A2， 2T2→4T2， and 4T2→4A2 transitions of Cr3+， respectively. The broad band emissions weaken and the R line becomes stronger and sharper at low temperature. The calculated results showed the crystal field strength Dq/B=2.32， Stokes displacement ΔES=1919cm-1 and Huang-Rhys factor S=5.58， which indicates that Cr3+ in Cd3Al2Ge3O12 garnet are located in a weak crystal field strength and the coupling between the electrons and the phonons is strong， The distance ΔE between 4T2 zero phonon energy level and 2E energy level is only 326.5cm-1， which is beneficial to the output of Cr3+ tunable laser.