Broadened and enhanced MIR emission in Yb3+/Er3+/Dy3+ triply-doped CaYAlO4 crystal

Yb³⁺/Er³⁺/Dy³⁺ triply-doped CaYAlO₄ single crystal was successfully grown to obtain the broadened and enhanced 3 μm MIR emission. The structure characters were studied by XRD measurement. The optical properties and energy transfer mechanism between Yb³⁺, Er³⁺, and Dy³⁺ were investigated according to the measured absorption spectra, emission spectra, and fluorescence decay curves. The absorption spectra show that the triply-doped crystal could be effective pumped by 980 nm due to the introduced of Yb³⁺ and Er³⁺. In comparison with Dy³⁺ singly-doped CaYAlO₄ crystal, a broadened and enhanced ∼3 μm MIR emission with a full width at half maximum (FWHM) of 286 nm was obtained due to the fact that there exists effective energy transfer process from Yb³⁺ and Er³⁺ to Dy³⁺. For Yb³⁺, it serves as an effective sensitized ion. For Er³⁺, it could be not only used as an effective sensitized ion, but also as a 2.7 μm MIR emission center. For Dy³⁺, it serves as a deactivating ion to solve the self-termination “bottleneck” effect of Er³⁺, and more importantly, as an emission center to achieve 3 μm emission. The comprehensive effect is to obtain enhanced and broadened MIR emission in the triply-doped crystal. In addition, the corresponding energy transfer efficiency from Yb³⁺: ²F_5/2 to Dy³⁺: ⁶H_5/2 is as high as 90 %. Hence, the Yb³⁺/Er³⁺/Dy³⁺: CaYAlO₄ crystal could be used as promising medium for MIR broadband tunable laser applications.