Yb: Borate Glass with High Emission Cross Section

The emission cross section for the2F5/2–2F7/2transition of Yb3+has been determined from absorption and emission measurements of some borate glasses at room temperature. By systematic variations in the spectroscopic properties with composition, a glass composition with emission cross sections of more than 1.70 pm2and fluorescence lifetimes longer than 1.0 ms is obtained; this composition has advantages over some excellent laser glasses reported in published papers.