Near-infrared emissions and quantum efficiencies in Tm 3+-doped heavy metal gallate glasses for S- and U-band amplifiers and 1.8 μm infrared laser

Abstract

Intense 1.8 μm and efficient 1.48 μm infrared emissions have been recorded in Tm 3+-doped alkali-barium-bismuth-gallate (LKBBG) glasses with low phonon energies under the excitation of 792 nm diode laser. The maximum emission cross-sections for 1.8 and 1.48 μm emission bands are derived to be 6.26×10 −21 and 3.34×10 −21 cm 2, respectively, and the peak values are much higher than those in Tm 3+-doped ZBLAN glass. In low-concentration doping, the full-widths at half-maximum (FWHMs) of the two emission bands are 223 and 122 nm, and the quantum efficiencies of the 3F 4 and 3H 4 levels are proved to be ∼100% and 86%, respectively. When the doping concentration increases to 1 wt%, the quantum efficiency of the 3H 4 level is reduced to 60% due to the cross-relaxation processes in high-concentration doping. Efficient 1.8 μm infrared emission in Er 3+/Tm 3+-codoped LKBBG glass has also been achieved under the excitation of 970 nm diode laser, and the probability and the efficiency of non-radiative energy transfer from Er 3+ to Tm 3+ are as high as 354 s −1 and 58.4%, respectively. Efficient and broad 1.8 and 1.48 μm infrared emission bands indicate that Tm 3+-doped LKBBG glasses are suitable materials in developing S- and U-band amplifiers and 1.8 μm infrared laser.