Menno F. Hazenkamp, Thomas C. Brunold and Hans-U. Güdel
Laser potential of CrO₄^3-- and MnO₄^2--doped crystals
J. Lumin. 72-74, 675-676 (1997)                 

Abstract: The broad emission band extending from 11000 to 6000 cm^–1 of both CrO₄^3-- and MnO₄^2--doped crystals is due to ligand-field transitions. The CrO₄^3--doped systems have very low luminescence quantum efficiencies, even at 15 K, a severe restriction for their use as laser materials. MnO₄^2--doped BaSO₄ on the other hand has a relatively high quantum efficiency of 20% at room temperature which makes this a promising laser material.