Influence of Stark splitting levels on the lasing performance of Yb(3+) in phosphate and fluorophosphate glasses.

Lasing properties have been investigated for Yb(3+) doped glasses with similar emission cross sections (σ(emi)) and lifetime while possessing different Stark levels. Narrow Stark splitting of Yb(3+)-phosphate glass is responsible for severe heat generation, narrow emission band and much smaller σ(emi) at lasing wavelength, making Yb(3+)-phosphate glass unsuccessful to achieve laser output, whereas 1.166W cw laser was obtained in Yb(3+)-fluorophosphate (FP) glass with broader Stark splitting. Analysis on laser system levels reveals that under room temperature, Yb(3+) laser is quasi-3.13-level in phosphate glass and quasi-3.36-level in FP glass. These demonstrations suggest that unless the Stark splitting is enlarged, conventional Yb(3+)-phosphate glass is not a good gain medium for bulk Yb(3+)-laser.