Preparation and Spectra Properties of Near-stoichiometric Cr∶LiNbO_3 Single Crystals Grown by Bridgman Method

The near-stoichiometric LiNbO3 single crystals doped Cr3+ in the raw compositions were grown by Bridgman method using K2O as flux,and taking high temperature gradient of about 60~ 80 ℃/cm of the interface as seeding and growing of the crystal. The composition of as-grown crystal were analyzed by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES),the content of Cr3+,Li2O and Nb2O3 were 0.62 mol%、49.23 mol% and 50.15 mol%,respectively. The FT-IR indicated that stretching vibration of OH- changes as the composition changing. The absorption and fluorescence were also measured,two wide absorption band centered at 480 nm and 658 nm which corresponded to the 4A2→4T1 and 4A2→4T2 level transition,and two weak absorption of R-lines were at 684 nm and 728 nm were observed. The fluorescence spectrrum showed a emission wideband ranging from 850 nm to 1150 nm excited by 670 nm pulse laser in room temperature. It was to note that the wide emission assigned to the Cr3+Ni and Cr3+Nb transition of 4T2→4A2 level. The crystal field and Racah parameters were also calculated.