Anti-stokes luminescence in Pr3+ activated crystalline ZBLAN (Zr, Ba, La, Al & Na) fluoride phosphor

Abstract

Infrared-to-visible up-conversion in Pr3+ activated ZBLAN fluoride crystalline phosphors has been investigated at room temperature for different activator concentrations. In the excitation spectra as well as in the emission spectra, initially the intensity increases with activator concentration, attains an optimum value and then it decreases with further increase in the activator concentration. It seems that blue excitation of the phosphor is due to Excited State Absorption (ESA) mechanism. The 2nd power dependence of the blue fluorescence from the (3)p(0) state under IR pumping of (1)G(4) state indicates a dominant two photon ESA mechanism. The mechanism of anti-Stokes luminescence in an unique optical activator Pr3+ in the ZBLAN fluoride host material, is discussed.