Optical Spectroscopy of Pr³⁺ Ion Singly Doped LiLuF₄ Single Crystal by Bridgman Method

High quality LiLuF₄ single crystals doped with various Pr³⁺ ions were synthesized by a vertical Bridgman method in completely sealed platinum crucibles. The excitation spectra spans from 420 nm to 500 nm. The prepared single crystals exhibit a blue band at 480 nm (³P₀→³H₄), a green band at 522 nm (³P₁→³H₅), and a red band at 605 nm (¹D₂→³H₄) when excited at 446 nm; their corresponding average lifetimes are 38.5 μs, 37.3 μs, and 36.8 μs, respectively, which are much longer than those in oxide single crystals. The effects of excitation wavelength and doping concentration on emission intensities and chromaticity coordinates are investigated. The optimal Pr³⁺ concentration is confirmed to be 0.5%. The temperature dependent emission shows that the emission intensity constantly decreases with the increase of temperature from 298 K to 443 K due to the enhancement of non-radiative quenching at high temperature. The ³P₀→³H₄ transition is the most vulnerable to temperature, followed by the ³P₁→³H₅ transition and ¹D₂→³H₄ transition.