Sensitization and deactivation effects of Ndon the Ho : 3.9 μm emission in a PbF crystal.

The use of Nd codoping for sensitizing the Ho ion and enhancing the ∼3.9  μm emission from Ho:I5→I5 was investigated in the PbF crystal for the first time, to the best of our knowledge. The ∼3.9  μm fluorescence emission properties and energy transfer mechanism of the as-grown crystals were investigated. The results show that the Nd ion can act as a sensitizer to the Ho ion, providing an efficient excitation channel, making the Ho/Nd:PbF crystal propitious to be pumped by commercialized InGaAs laser diodes (LDs). Moreover, an enhanced ∼3.9  μm emission was obtained in the Ho/Nd:PbF crystal due to the codoping of Nd ions, leading to an efficient energy transfer from a lower laser level of Ho:I5 to Nd:I4, while having little influence on the higher laser level of Ho:I5. These advantageous spectroscopic characteristics indicate that the Ho/Nd:PbF crystal might have potential application in ∼3.9  μm mid-infrared lasers under a conventional 808 nm LD pump.