Luminescence from Pr3+ P-3(1) and P-3(2) states in beta-NaYF4:Pr3+

Strong luminescence signals were observed from Pr3+ P-3(1) states in beta-NaYF4:Pr3+ compounds under one-color and three-color pumping. The feeding of P-3(1) is shown to involve a two-ion interaction, coupled with a thermalization process from P-3(0) levels. The efficiency of this mechanism is assumed to be due to the small P-3(0)-P-3(1) gap (590 cm(-1)) and to strong resonances between Pr3+ levels. The latter is improved by the multisite character of the host structure, which contributes to broaden the Pr3+ levels by Stark effect. In contrast, the P-3(2) states are fed exclusively from radiative de-excitations from S-1(0) states.