Evolution of Cr 4+ , Cr 3+ and Cr 2+ contents in Cr:Mg 2 SiO 4 crystals during those oxidizing annealing

The evolution of Cr 4+ , Cr 3+ and Cr 2+ contents in Cr:Mg 2 SiO 4 crystals during those prolonged high-temperature oxidizing annealing have been studied. The concentration of Cr 4+ increases by factor of 1, 5-2, 5, whereas the parasitic Cr 2+ ions practically disappear during such annealing. Therefore this post-growth treatment of Cr:Mg 2 SiO 4 crystals considerably enhances their spectroscopic properties as the active laser media.