Abstract

Pr³⁺-doped fluorides, in particular LiYF₄ (YLF) and GdLiF₄ (GLF), are promising laser materials for the visible spectral range. Recently, pulsed laser action of Pr: GLF¹ and cw laser action of PriYLF² have been realized at room temperature on several visible transitions as well as cw laser action of Pr:GLF and Pr:KYF₄ (Pr: KYF) on the ³P₀ → ³F₂ transition at 639 nm and 642.5 nm, respectively. In this work the influence of the anisotropy of the host lattice on the spectroscopic parameters was compared with the laser data of Pr-doped YLF and GLF. Pr:KYF was also investigated. Due to the large number of energy levels of the Pr³⁺ ion, Pr-doped crystals exhibit several absorption and emission lines. The fluorescence spectra of Pr-doped YLF, GLF, and KYF are shown in Fig. 1. While the absorption and fluorescence spectra of Pr:YLF and Pr:GLF are very similar, the absorption and emission lines of Pr:KYF are inhomogeneously broadened because there are six different rare earth sites in the host lattice.³'⁴ The emission cross-sections σ_em of the pulsed laser transitions of Pr:GLF² and the cw laser channels of Pr:YLF² obtained from the fluorescence spectra are summarized in Table 1. The lifetime of the thermally coupled ³P₀ and ³P₁ states which are the upper laser levels of the investigated visible laser transitions in Pr-doped YLF, GLF, and KYF is about 37 µs, 40 µs, and 53 µs, respectively.

© 1994 IEEE