title: Fluorescence quantum efficiency measurements in the presence of Auger upconversion by the thermal lens method.
abstract: Mode-mismatched thermal lens (TL) measurements in Cr3+-doped fluoride crystals (LiSrAIF6 and LiSrGaF6) are reported. A nonlinear increase of the TL signal, and decrease of quantum efficiency, with increasing excitation power was observed and attributed to energy-transfer upconversion (ETU). Assuming an upconversion rate that is proportional to the excited-state population, Wup = gammaN(e), the theoretical model developed fits the experimental data well. The ETU parameters (gamma) were determined with unprecedented accuracy for low Cr concentrations. Thermo-optical parameters (K, ds/dT) were also obtained.
authors.affiliation: Istituto de Física de São Carlos, Universidade de São Paulo, C.P. 369, CEP 13560-970, São Carlos, São Paulo, Brazil. vpilla@if.sc.usp.br
authors.forename: Viviane
authors.initials: V
authors.lastname: Pilla
authors.forename: Tomaz
authors.initials: T
authors.lastname: Catunda
authors.forename: Hans P
authors.initials: HP
authors.lastname: Jenssen
authors.forename: Arlete
authors.initials: A
authors.lastname: Cassanho