Journal of Luminescence 91 (2000) 147–153 Temperature-dependent spectroscopic analysis of F2

A temperature-dependent spectroscopic analysis of the color center laser medium, LiF: F2 +**, is shown. Special attention is devoted to the well-known F2 +* * color center as well as a new F2 +**-like color center, conclusively discovered in this work, which is found to have a peak absorption near l0abs 808 nm and peak emission near l0ems 1080 nm. Justification for the association of this new center with F2+**-like color centers is explained in the text. Standard F2 +* * color centers have kinetics of fluorescence lifetime of t13 K 32 ns, t300 K 21 ns, for a quantum eciency of fluorescence, Z 66%. Concerning the new F2+**-like color center, the 13K lifetime was found to be t 5 ns. We show that Alexandrite laser radiation can simultaneously excite the absorption bands of both F2+**-like centers in their region of spectral overlap. The resulting emission from both centers is the mechanism responsible for the ultrabroadband range of tunability, 800–1300 nm, from this laser medium at RT. This crystal is the heart of a potential ultrabroadband, near-IR laser; frequency doubling this fundamental output will realize a truly white-ligh