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

Using a pump probe technique, absolute excited state absorption cross secti ons are measured in various Er3+ doped laser crystals in a wavelength domai n extending from 0.53 to 2.9 mu m. The gain cross section around 2.8 mu m a nd 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. Th e cross sections for the transitions involved in the upconversion pumping p rocesses of the characteristic green emission of Er:LiYF4 are also estimate d and discussed. A comparison is made between these results and those obtai ned semi-theoretically by using the Judd-Ofelt formalism.