Bandwidth enhancement of ∼3 μm emission and energy transfer mechanism in Yb3+/Ho3+/Dy3+ co-doped PbF2 crystal

The ∼3 μm emission in Yb3+/Ho3+/Dy3+ doped with PbF2 crystal is investigated in this paper. The involved energy transfer mechanisms between Yb3+/Ho3+/Dy3+ in PbF2 crystal is explained in detail. As far as we know, it is the first time to report a broadband emission extending from about 2600 to 3400 nm with a maximum full width at half maximum (FWHM) of 283 nm obtained in Yb0.02Ho0.02Dy0.02: Pb0.94F2 crystal under 970 nm pump. The energy transfer efficiency from Ho3+: 5I7 to Dy3+: 6H13/2 is as high as 97.9%, and the Ho3+: 5I6 → 5I7 fluorescence lifetime ratio τ(5I6)/τ(5I7) in the Yb0.02Ho0.02Dy0.02: Pb0.94F2 crystal was calculated to be 105.1%, indicating that Dy3+ ion is to be an efficient deactivated ion for Ho3+ ion to greatly facilitate the Ho3+: 5I6 → 5I7, while also broaden the mid-infrared lasers operating in the wavelength region ∼3 μm. All imply that Yb0.02Ho0.02Dy0.02: Pb0.94F2 crystal can be a potential candidate for the development of solid-state lasers operating in the mid-infrared broadband emission.