Activation and deactivation effects to Ho^3+ at ~28 μm MIR emission by Yb^3+ and Pr^3+ ions in YAG crystal

Abstract

The use of Yb3+ and Pr3+ co-doping with Ho3+ to enhance the Ho3+:5I6→5I7 ~2.8μm emissions are investigated in the YAG crystal for the first time. Absorption spectra of the Yb:Ho:YAG and Yb:Ho:Pr:YAG crystals find that doping of Yb3+ increase absorption intensity within 850-1050nm and make the crystals suitable to high-power InGaAs LDs. Fluorescence spectra show that ~2.8μm lasers may be realized on both crystals at different wavelengths, with the maximum emission cross section of 1.69 × 10−20 cm2 at 2780 nm for Yb:Ho:Pr:YAG and 1.23 × 10−20 cm2 at 2848 nm for Yb:Ho:YAG. Lifetime results and energy transfer analyses indicate that activator Yb3+ ions can prolong the higher laser level of Ho3+: 5I6 and deactivator Pr3+ ions are able to depopulate the lower laser level of Ho3+: 5I7, both beneficial to population inversion and contributed to facilitate ~2.8μm laser operations. All these results indicate that Yb:Ho:Pr:YAG crystal is a promising laser medium for LD-pumped ~2.8μm laser applications.