Spectral Properties and Upconversion Luminescence of Er3+, Yb3+: BaWO4 Crystal

The optical quality of Er3+, Yb3+: BaWO4 crystal was grown by Czochralski method. Absorption spectra were measured and energy levels were assigned. According to Judd-Ofelt theory, the spectral strength parameters of Er3+ ion were fitted to be ω2 =0.3926 x 10−20 cm2, ω4 =0.0721 x 10−20 cm2, ω6 =0.0028 x 10−20 cm2. Emission peaks centered at around 523, 544 and 670 nm were observed under 334 nm He-Cd laser excitation and emission peaks centered at 1001 and 1534 nm were detected under 976 nm laser excitation. Strong green emission was also observed when the crystal was pumped with 808 nm and 976 nm laser. The mechanisms of frequency upconversion and sensitization were analyzed.