Enhanced broadband 3 μm emission in Yb³⁺/Dy³⁺:YAlO₃ crystal under 979 nm excitation

Yb³⁺ ion was introduced as a sensitizer for commercial 980 nm pump source utilization in Yb³⁺/Dy³⁺ co-doped YAP crystal for the first time. An intense broadband 3 μm emission (Dy³⁺:⁶H_13/2 → ⁶H_15/2 transition) in Yb³⁺/Dy³⁺:YAP crystal was demonstrated. As compared with Dy³⁺ singly-doped YAP crystal under 802 nm OPO excitation, the larger emission cross-section (=4.25 × 10⁻²¹ cm²) and effective emission bandwidth (=316 nm) were obtained in Yb³⁺/Dy³⁺:YAP crystal under 979 nm OPO laser excitation, which make it favorable for tunable lasers. The energy transfer efficiency from Yb³⁺ to Dy³⁺ was obtained as high as 97.2%. The greatly reduced near-infrared emission of Yb³⁺:²F_5/2 → ²F_7/2 transition and largely shortened lifetime of Yb³⁺:²F_5/2, also reveal the efficient energy transfer from Yb³⁺ to Dy³⁺. The energy transfer micro-parameters were calculated by spectral overlapping integral method, and the main energy transfer channel is determined. In addition, the energy dispersive X-ray spectroscopy, X-ray diffraction and Raman spectrum were measured in Yb³⁺/Dy³⁺:YAP crystal. Rietveld refinement was also employed to investigate the variation in lattice parameters in Yb³⁺/Dy³⁺:YAP crystal. It can be concluded that Yb³⁺/Dy³⁺:YAP is an excellent candidate for achieving mid-infrared laser.