Cr3+doped Ca3(VO4)2: A new tunable laser crystal

A new near-infrared tunable laser crystal, Cr ³⁺ doped Ca ₃(VO ₄) ₂ crystal (Cr: CVO) is grown by the Czochralski method for the first time. The crystal structure and thermal expansion of Cr: CVO crystal are investigated in detail. The substitution of Cr ³⁺ for Ca ²⁺ is confirmed by the formation energy calculation. The Cr: CVO crystal has a strong and broad absorption at visible wavelength and a broad emission in the near-infrared. The absorption cross-section in the σ direction is about 1.56 times that in the π direction at 690 nm. A broadband emission extends from 750 nm to 1200 nm with the full width at half maximum 185 nm and 178 nm in the σ and π direction, respectively. The crystal field and electron-vibration coupling are discussed, as well as the origin of the broadband emission. While Cr ³⁺ ions substitute other ions with a large difference in ionic radii and charges such as Ca ²⁺ ions, the lattice distortion and vacancy may be produced, leading to the severe distortion of the octahedron and the broadening of the emission band. Our work guides the design of broadband luminescent materials and confirms that Cr: CVO is a potential candidate for tunable laser crystals.