Effective sensitization of Dy3+:6H11/2 energy level by Tm3+ ions in KPb2Br5 crystal for 4.3 µm lasers

To the best of our knowledge, this is the first study to investigate the use of Tm 3+ to sensitize the Dy 3+ ion and enhance the ∼4.3 µm emission from Dy 3+ : 6 H 11/2 → 6 H 13/2 in the KPb 2 Br 5 (KPB) crystal. The ∼4.3 µm fluorescence emission properties and energy transfer mechanism of the Dy:KPB and Tm,Dy:KPB crystals were examined. The results show that Tm 3+ is an excellent sensitizer to the Dy 3+ ion and can provide an efficient excitation channel; thus, the Tm,Dy:KPB crystal can be pumped by a commercial 808 nm laser diode (LD). Compared with the Dy:KPB crystal, co-doping with the Tm 3+ ion improves the absorption around 800 nm by an order of magnitude, and the energy transfer efficiency from Tm 3+ : 3 F 4 to Dy 3+ : 6 H 11/2 is as high as 76.7%, indicating that the Tm,Dy:KPB crystal has great potential application in ∼4.3 µm mid-infrared lasers under a commercial LD pump.