Absolute excited state absorption cross section measurements in Er3+:LiYF4for laser applications around 2.8 µm and 551 nm

Using a pump-probe technique, absolute excited state absorption cross sections are measured in various Er 3+ doped laser crystals in a wavelength domain extending from 0.53 to 2.9 µm. The gain cross section around 2.8 µm and the population ratio between the involved levels 4 I 11/2 and 4 I 13/2 are measured for different Er 3+ concentrations and pumping wavelengths. The cross sections for the transitions involved in the upconversion pumping processes of the characteristic green emission of Er:LiYF 4 are also estimated and discussed. A comparison is made between these results and those obtained semi-theoretically by using the Judd-Ofelt formalism.