Emission spectrum and simulated laser parameters of Yb3+:LiLu(WO4)2 crystal

Crystal growth and spectroscopic study of the new compound Yb³⁺:LiLu(WO₄)₂ have been undertaken for the first time. Preliminary growth using flux method with Li₂W₂O₇ as solvent allows us to obtain small single crystals. As a promising laser crystal, Yb³⁺:LiLu(WO₄)₂ have characteristics of a low concentration quenching effect and low laser threshold owing to the existence of covalent bands in WO₄ group. Its absorption peak at 977 nm, corresponding to ²F_7/2(1) → ²F_5/2(5) transition, is suitable for laser diode pumping. Emission spectrum shows large bands extending from 900 to 1100 nm, five peaks centred respectively at 959, 978, 997, 1025 and 1056 nm are well resolved. The FWHM of the most intense emission band located at 997 nm is about 20 nm. Energy Stark levels are: 0, 201, 469 and 749 cm⁻¹ for the ²F_7/2 component and: 10,230, 10,427 and 10,890 cm⁻¹ for the ²F_5/2 component. The overall splitting of ²F_7/2 ground-state manifold is 749 cm⁻¹, which is larger than that observed in similar systems such as Yb³⁺:LiLa(WO₄)₂ (632 cm⁻¹). Such large crystal-field splitting of the ²F_7/2 ground-state will be advantageous to lower laser thermal effect and re-absorption losses. As we can see, the stark electronic levels are characterized by relatively large crystal-field splitting favourable to laser crystal applications in the near infrared spectral region.