Laser crystal with at least two co-dopants

An amplifying medium for at least one of emitting and amplifying a light beam by laser effect, consisting of an X—F2 doped crystal, where X refers to a chemical element of the alkaline earth family and F refers to fluorine, and where the crystal is doped with trivalent ions of rare earth, called dopant ions, said dopant ions comprising:

• a first category of optically active dopant ions, in which each dopant ion is an ion of a first rare earth;
• and
• a second category of dopant ions, called buffer ions, optically inactive in that they do not directly cause the laser effect utilized in the doped crystal, being used only to limit formation of aggregates of several ions of the first category of dopant ions, wherein each dopant ion of the second category is an ion of a rare earth distinct from the first rare earth;
• wherein the second category of dopant ions includes at least ions of a second rare earth and ions of a third rare earth, the second rare earth and the third rare earth being distinct from each other;
• and
• wherein the ions of the second rare earth and ions of the third rare earth are associated with elemental fluorescence spectra centered on respective central wavelengths at least 3 nm apart, where each elemental fluorescence spectrum refers to a fluorescence spectrum of the same crystal, doped with the same dopant ions of the first category of dopant ions and co-doped only with ions of the second rare earth, respectively the third rare earth.