Enhanced emission of 286 μm from diode-pumped Ho^3+/Yb^3+-codoped PbF_2 crystal

A novel Ho(3+)Yb(3+)-codoped PbF(2) mid-IR laser crystal was successfully grown and analyzed. Enhanced emission at 2.86 μm was observed from the crystal under excitation of a common 970 nm laser diode for the first time. The effect of Yb(3+) codoping on the 2.86 μm photoluminescence of Ho(3+) was investigated. In comparison to Ho(3+)-singly doped PbF(2) crystal, the Ho(3+)/Yb(3+)-codoped PbF(2) crystal possessed comparable quantum efficiency (88.8%), and fluorescence branching ratio (20.52%) along with a larger calculated emission cross section (1.90×10(-20) cm(2)) corresponding to the laser transition (5)I(6)→(5)I(7) of Ho(3+). It was found that the introduced Yb(3+) enhanced the 2.86 μm emission by depopulating the Ho(3+):(5)I(7) level. The energy transfer (ET) efficiency from Yb(3+):(2)F(5/2) to Ho(3+):(5)I(6) is as high as 96.7%, indicating that Yb(3+) ion is an effective sensitizer for Ho(3+) ion in PbF(2) crystal. These results suggest that Ho(3+)/Yb(3+)-codoped PbF(2) crystal may become an attractive host for developing solid state lasers at around 2.86 μm under a conventional 970 nm LD pump.