Effect of Yb3+ doping on upconversion emission intensity and mechanism in Er3+/Yb3+-codoped fluorozirconate glasses under 800 nm excitation

Er3+ singly- and Er3+/Yb3+-codoped fluorozirconate glasses were prepared. T he upconversion emission intensities of the Er3+ ion around both 550 and 66 0 nm were measured under 800 nm excitation. The absorption band of the Yb3 ion is located around 980 nm. Though the absorption band of Yb3+ does not interact directly with the incident light at 800 nm, both upconversion inte nsities around 550 and 660 nm emission increased with the increasing YbF3 c oncentration. We calculated the upconversion intensities around 550 and 660 nm by using rate equations and evaluated the principal upconversion mechan ism in Er3+ singly- and Er3+/Yb3+-codoped samples quantitatively. We also i nvestigated the reason for the increase of the upconversion emission intens ities with the codoping of Yb3+ under 800 nm excitation. (C) 1999 American Institute of Physics. [S0021-8979(99)03023-6].