Abstract

It has been shown that Pr,Yb-doped YLiF₄ (YLF) is a suitable upconversion laser material. Under excitation with a Ti:sapphire laser tuned to an emission wavelength of about 830nm, 75mW of red output on the transition Pr³⁺(³P₀) →Pr³⁺(³F₂) at 639.5nm were obtained. Experimental observations indicate that an avalanche process is the main upconversion mechanism leading to population of the ³P_J multiplets of Pr³⁺.The metastable intermediate energy level required for upconversion is the Pr³⁺(¹G₄) multiplet [1].Recently a significant improvement of red output in YLF was achieved by optimizing the Pr- and Yb- concentration. The best composition was Pr(3%),Yb(5%):YLF. Moreover green and yellow upconversion lasing have been demonstrated. Since the host lattice YAlO₃ (YAP) has turned out to be a good material for laser crystals [2], YAP doped with various concentrations of Pr and Yb have been investigated for a similar upconversion mechanism. Spectroscopic measurements were carried out on Czochralski-growm crystals, with melt compositions Pr(0.5%),Yb(5%):YAP, Pr(0 75%),Yb(5%):YAP and Pr(0.8%),Yb(5%):YAP. The respective dopant concentrations refer to the Y sites.

© 1998 IEEE