Structure, first-principles calculations and yellow spectral properties of Dy3+: CaLaGa3O7 single crystal

Abstract

High optical quality Dy3+-doped CaLaGa3O7 (abbreviated as Dy: CLGO below) crystal was grown successfully by the Czochralski technique along the (0 0 1) orientation. The lattice parameters of the as-grown crystal were obtained by Rietveld refinement to its XRD pattern. The electronic structures including band structure and density of state (DOS) were calculated by using first-principles calculations based on density functional theory (DFT). The spectroscopic characteristics of Dy: CLGO are investigated, with special attention to the yellow emission that could be pumped directly by the rapidly developed blue GaN LD. Based on the Judd-Ofelt (J-O) theory, the intensity parameters from the measured line strengths were determined. The J-O parameters were used to predict radiative transition probabilities, radiative lifetime and branching ratios for various excited levels of the Dy: CLGO crystal. The absorption cross-sections of Dy: CLGO at 453 nm are calculated to be 0.14 × 10−20 cm2 and 0.11 × 10−20 cm2 for π- and σ-polarizations, respectively. Meanwhile, Dy: CLGO exhibits strong yellow emission at 574 nm corresponding to the transition 4F9/2 → 6H13/2 with stimulated emission cross-sections of 3.88 × 10−21 cm2 and 3.42 × 10−21 cm2 for π- and σ-polarizations, respectively. The relatively long fluorescence lifetime (565 μs) indicates a high laser efficiency of the crystal. All results suggest that Dy: CLGO crystal could be a promising candidate for yellow laser at 574 nm pumped by blue GaN LD.