Sensitization and deactivation effects of Nd^3+on the Ho^3+ : 39 μm emission in a PbF_2 crystal

Abstract

The use of Nd³⁺ codoping for sensitizing the Ho³⁺ ion and enhancing the ∼3.9 μm emission from Ho³⁺:I₅5→I₆5 was investigated in the PbF₂ 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 Nd³⁺ ion can act as a sensitizer to the Ho³⁺ ion, providing an efficient excitation channel, making the Ho³⁺/Nd³⁺:PbF₂ crystal propitious to be pumped by commercialized InGaAs laser diodes (LDs). Moreover, an enhanced ∼3.9 μm emission was obtained in the Ho³⁺/Nd³⁺:PbF₂ crystal due to the codoping of Nd³⁺ ions, leading to an efficient energy transfer from a lower laser level of Ho³⁺:I₆5 to Nd³⁺:I_15/24, while having little influence on the higher laser level of Ho³⁺:I₅5. These advantageous spectroscopic characteristics indicate that the Ho³⁺/Nd³⁺:PbF₂ crystal might have potential application in ∼3.9 μm mid-infrared lasers under a conventional 808 nm LD pump.