Radiative lifetimes and fractional thermal loading of Yb/sub 3/Al/sub 5/O/sub 10/ (YbAG) and highly-doped Yb:Y/sub 3/Al/sub 5/O/sub 12/ (Yb:YAG)

Summary form only given. Combined with appropriate laser designs such as the thin disk and waveguide architectures, highly-doped solid-state laser materials offer the potential for higher average power scaling and improved thermal management. Because stress fracture is limited by thermal gradient, the ability to keep the gain element thin while still having sufficient rare earth ion density to absorb the pump light can allow higher pump intensities and efficiencies. To date impurities in the crystals have limited the usefulness of high concentration Yb:YAG. At higher Yb/sup 3+/ concentrations, energy migration makes the fluorescence lifetime and fractional heat loading particularly sensitive to defects. The work described here addresses some of the questions that have been raised regarding the maximum useful Yb/sup 3+/ concentration in YAG. We systematically measured the fractional heat loading, radiative lifetimes and other material properties.