Spectroscopic analyses of Tm3+/Yb3+: BaGd2(MoO4)4 crystal for mid-infrared applications

A Tm3+/Yb3+ co-doped BaGd2(MoO4)4 crystal was successfully grown and analyzed. The use of Tm3+ codoping for enhancement of the transition of Tm3+:3F4 → 3H6 ∼ 2 μm emissions was investigated. Compared with Tm3+ singly-doped BaGd2(MoO4)4 crystal, the Tm3+/Yb3+ codoped BaGd2(MoO4)4 crystal possessed a longer fluorescence lifetime (2.467 ms), higher fluorescence emission cross section (1.174 × 10−20 cm2) corresponding to the stimulated emission of Tm3+ :3F4 → 3H6 transition. The ∼2 μm emission characteristics and energy transfer were investigated in detail. The energy transition efficiency from Tm3+:3H4 level to Yb3+:2F5/2 level, and from Yb3+:2F5/2 level to Tm3+:3H5 level were calculated to be 0.52 and 0.75, respectively. It indicates that Yb3+ can act as an effective bridge between 3H4 level and 3F4 level of Tm3+ to obtain efficient 1.9 μm emission under being pumped by a conventional 782 nm LD. Therefore, Tm3+/Yb3+ co-doped BGM crystal is a promising candidate for mid-infrared applications.