Ho^3+/Er^3+ co-doped fluoride glass sensitized by Tm^3+ pumped by a 1550  nm laser diode for efficient 20  μm laser applications

In the present Letter, a high-emission intensity of 2.0 μm is reported for Ho(3+)/Er(3+) co-doped fluoride glass sensitized by Tm(3+) ions under 1550 nm excitation. The measured absorption spectra do not show clustering in the local ligand field, which also demonstrates that Er(3+) ions are efficiently excited by pumping and energy transfer (ET) to Ho(3+) and Tm(3+) ions. The enhanced Ho(3+):2.0 μm emission has a maximum emission cross section (4.8×10(-21) cm(2)). An ET mechanism based on the enhanced 2.0 μm emission and other reduced near-infrared emissions is discussed. Results show that the addition of Tm(3+) ions populates the Ho(3+):(5)I(7) level through the channel at the Tm(3+):(3)F(4) level between Er(3+) and Ho(3+) ions. The spectroscopic characteristics and thermal property of Er(3+)/Ho(3+)/Tm(3+) tri-doped ZBYA glass reveal that the material is an attractive host for 2.0 μm lasers.