The influence of doping on the laser performance

We report a comparison, at low inversion population density, between two Yb:YAG ceramics lasers with different doping levels (10 and 20 at %) emitting at 1030 and 1050 nm. At the shorter lasing wavelength, the efficiency and the maximum output power of both samples are almost independent on the concentration of dopants. Conversely, at 1050 nm the two samples show a sizeable difference in the performances for higher values of the pump power. The results are compared with numerical simulations accounting for the pump beam and the laser radiation in order to map the temperature distribution experienced by the samples. We studied the effects of the reinjection of the pump inside the active medium. We obtained an output power of 10 W with a slope efficiency of 59% in respect of the pump power on the 20 at % sample. Finally, we report the tuning range for the heavier-doped sample (20 at %), which, to the best of our knowledge, is the first measurement on an heavily doped sample even reported in literature.