Rare earth doped AlF3-based flouride glass

Energy transfers and upconversion fluorescence spectroscopy in both Er3+ singly doped and Tm3+-Yb3+ co-doped AlF3-based flouride glass,excited at 970 nm,are investigated experimentally. In Er3+ :AYF glass,the optium Er3+ content for 550 nm emission is about at 6 mol%,which is 12 mol% in AZF glass. With the increase of E3+ content,the intensity ratio of the red emission to the green emission ( I-red/I-green) is increased in AYF and AZF glass,and the red emission intensity in these gass depends on (p(ex))(1.6). They are mainly due to a cross-relaxation process between two erbium ions,one in the S-4(3/2) and the other in the I-4(9/2) In Tm3+-Yb3+ co-doped AlF3-based flouride glass,the concentration quenching of Tm3+ in blue at 476 nm is stronger than that in infrared light at 793 nm,and the optimum content of Tm3+ for 476 nm emission is about 0.1 mol%,while it is (0.3-5)mol% for 793 nm emission. The concentration quenching of Yb3+ to upconvertion fluorescence is also observed. It may be due to the back-energy transfer from the F-3(4) level of Tm3+ to the F-2(5/2) level of Yb3+.