Infrared (Er)BaY2F8 laser pumped through di‐ and tri‐ionic upconversion processes

Emission and absorption spectra of (5% Er) BaY2F8 were studied at 300, 77, and 4.2 °K. Stark‐level positions were determined from the liquid‐helium absorption spectra. Emission spectra were excited with a UV flash lamp and 1.53‐μm radiation from an Er:glass laser; in the latter case, the visible and near‐IR fluorescence of the Er3+ ions was excited through a multiphoton upconversion process. The lifetimes of Er3+‐ion‐excited states were measured at 300 and 77 °K. Laser action was stimulated at 0.85, 1.73, and 2.796 μm in a (5% Er) BaY2F8 laser rod using the transitions 4S3/2→4IJ, where J=13/2, 9/2, and 4I11/2→4I13/2, respectively. A Xe flash lamp was used for optical pumping. The latter two laser transitions were also pumped through upconversion of 1.53‐μm radiation of the Er:glass laser. The cross‐relaxation ion‐pair conversion coefficient for the 4I13/2 levels of the Er3+ ions in BaY2F8 was calculated to be α=3.7×10−17 cm−3 s−1.