The investigations of yellow spectral performances in potentially efficient Dy3+:BaF2 and Dy3+/RE3+ (RE = Tb, Eu):BaF2 crystals

Abstract

High quality Dy3+: BaF2 and Dy3+/RE3+ (RE = Tb, Eu): BaF2 crystals were successfully grown by temperature gradient technology (TGT). The visible spectroscopic properties as well as the energy transfer mechanism of Dy3+ and Tb3+/Eu3+ co-doped BaF2 crystals were systematically discussed. The spectral performance at 575 nm (Dy3+: 4F9/2 → 6H13/2) emission was significantly improved by co-doping Tb3+/Eu3+ ions. Through the upper level lifetime changed, it can be proved that there is a quasi resonance energy transfer between Dy3+: 6H13/2 and Tb3+: 7F4 / Eu3+: 7F4 states, and the final gain effect exceeds negative influence of the upper level energy transfer. Meanwhile, the optimal concentration ratio of Dy3+/Tb3+ and Dy3+/Eu3+ in double-doped crystals was relatively different. The optimal ratio of Dy3+/Tb3+ was 10:1 in 2%Dy3+,0.2%Tb3+: BaF2 crystal. The emission cross section increases from 8.147 × 10−22 cm2 to 11.284 × 10−22 cm2 with an increase of 38.5 %, and the quality factor (σem⋅τ) increases by 22.3 %. The optimal ratio of Dy3+/Eu3+ was 20:1 in 2%Dy3+,0.1%Eu3+: BaF2 crystal, the emission cross section is increased to 10.411 × 10−22 cm2 with an increase of 27.8 %, and the quality factor increases by 26.9 %. The above results show that Dy3+: BaF2 crystals co-doped with deactivated ions (Tb3+/Eu3+) of low concentration have great potential as gain media for yellow laser output.