Spectroscopic properties of Er3+/Yb3+/Ho3+:CaLaGa3O7 and Er3+/Yb3+/Eu3+:CaLaGa3O7 crystals used in mid-infrared lasers

Abstract

Er3+/Yb3+/Ho3+:CaLaGa3O7 (abbreviated as Er/Yb/Ho:CLGO) and Er3+/Yb3+/Eu3+:CaLaGa3O7 (Er/Yb/Eu: CLGO) crystals were grown by Czochralski technology and detailed spectroscopic analyses were carried out. The effects of Ho3+ and Eu3+ on the spectroscopic properties and mutual energy transfer mechanisms were investigated. It is found that the introductions of Ho3+ and Eu3+ are helpful in achieving enhanced mid-infrared (MIR) emission, as well as reduced near-infrared emission. Furthermore, the introduction of Ho3+ and Eu3+ depopulated the lower laser level through energy transfer and thus reduced the fluorescence lifetime of Er3+:4I13/2 in Er/Yb/Ho:CLGO and Er/Yb/Eu:CLGO crystals without significantly affecting the fluorescence lifetime of the upper laser level Er3+:4I11/2, which reduces the self-saturation problem to a degree. As a result, Eu3+ is a more appropriate deactivated ion than Ho3+ for Er3+ in this crystal. So Er/Yb/Eu:CLGO crystal could be a potential MIR gain medium for an enhanced 2.7 μm laser.