Absolute excited state absorption cross section measurements in Er3+:LiYF4 for laser applications around 2.8 μm and 551 nm

Using a pump probe technique, absolute excited state absorption cross sections are measured in various Er3+ doped laser crystals in a wavelength domain extending from 0.53 to 2.9 mu m. The gain cross section around 2.8 mu m and the population ratio between the involved levels I-4(11/2) and I-4(13/2) are measured for different Er3+ concentrations and pumping wavelengths. The cross sections for the transitions involved in the upconversion pumping processes of the characteristic green emission of Er:LiYF4 are also estimated and discussed. A comparison is made between these results and those obtained semi-theoretically by using the Judd-Ofelt formalism.