Inhomogeneous broadening of optical transitions in Yb:CaYAlO4

Yb:CaGdAlO4 is a promising laser media for femtosecond impulsions in the infrared, because of a broad emission line around 1 μm. This feature is related to the crystal structure where the doping ion, which substitutes Gd3+, is located in a disordered environment where Ca2+ and Gd3+ are randomly distributed on a same crystallographic site. Since Gd3+ ions prevent any EPR measurement to be carried out, CaYAlO4, which is isostructural to CaGdAlO4, has been studied, in the present work. The origin of the broadening of the optical absorption and emission lines has been studied by low temperature optical spectroscopy on CaYAlO4. Two families of sites have been highlighted and are related to the broadening of optical transitions.